BANGKOK DIGITAL CAMERA

Digital Zoom: How they word and which is the best

2011-08-27T00:50:00.000-07:00

Digital Zoom: How they word and which is the best?

Although there has been information concerning digital zooms on megapixel.net for nearly 4 years, digital zooms have continued to evolve. Moreover, to this day, one of the more frequent questions we get asked remains "what is a digital zoom?".

The concept behind the digital zoom is actually very simple, but often, the way it is presented as an extension of the optical zoom, creates confusion. Examples of this are common: a 10X optical zoom suddenly becomes a whopping 60X zoom, as a 6X digital zoom is tacked on to the actual focal length of the lens. This puffery may make the numbers more impressive, but are quite misleading for the uninitiated.

The digital zoom is primarily a cropping system and not as labelled: a "zoom". A real optical zoom is a lens which can bring the photographer closer to the subject, much like a telescope can. A digital zoom on the other hand is merely a system that cuts the central part of a digital image in such a way that it corresponds approximately to the field of view that a longer optical lens would show.

Here is a simple example. The photo shown at right is captured with an optical zoom which, in this case, corresponds to a 42mmfocal length.

The original image is captured with a 6 megapixel camera, which yields an image size of 3024 x 2016 pixels, and is reduced to a size of 400 x 267 pixels, to show here.

The subject at the centre of the frame is some distance away, but if we crop the original image to the size shown above, a 400 x 267 pixel frame allows us to show the subject in the same physical space on this page.

This is exactly what the digital zoom does. It simply crops the image. At this stage, the image quality remains the same as it was in the original image.

Obviously, a system that allows this type of cropping to be done directly with the camera can be useful, but most digital zooms take the process one step further. Indeed, what happens afterwards is critical to the image quality, either it remains the same as it was in the original full-size frame, or it gets degraded. Currently, there are 2 very different types of digital zooms. One type interpolates the image back to the size of the image the crop was taken from, the other leaves the cropped image as is. We'll start by looking at the first type of digital zoom.

With most digital zooms, the cropped section from the full size frame is interpolated to create an image that has a horizontal and vertical size that is same as the image size currently selected on the camera. The interpolation process that takes that small cropped section and brings it up to a much larger size involves the use of complex algorithms, and takes place in the camera. The sizing up process is done by adding pixels in between the existing ones, matching their colour. Since only the original pixels in the cropped section recorded actual information, the interpolation process cannot add detail.

Since the pixels that made up detail for the image are multiplied, the inevitable result is that the image becomes coarser. In fact, the larger the image size increase achieved by interpolation, the greater the degradation of the image.

With our example above, if we were to take the crop we made and increased its size to match the size of the frame it came from, we would need to blow it up by 756%.

Shown here is a comparably size section (400 x 267 pixel) taken from the crop shown above which has first been interpolated up to 3024 x 2016 pixels, resulting in a severe loss of detail.

Although most digital zooms don't go to this extreme — a 756% magnification would be equivalent to a 7.56X digital zoom— the principle is nevertheless the same, and the image quality invariably decreases. Commonly, digital zooms apply a lesser interpolation, as otherwise the image quality declines precipitously.

With the majority of cameras, the digital zoom crops from the optically magnified image. In other words, the crop is made from what the camera captures at the full telephoto setting of the lens. The examples below show the process:

The entire image shown above and to the left is what is captured with the camera's optical zoom. The yellow frame is equivalent to the area a 3X digital zoom would select from this frame.

In the image above on the right, the digital zoom "discards" the rest of the image, shown by a yellow overlay, and selects the centre.

The last photo, shown at left, is the resulting digitally zoomed image. The cropped section has been interpolated by 300%, resulting in an image that has the same dimensions as the one it came from.

The other type of digital zoom has appeared more recently, and is often referred to as the "Smart Zoom". The Smart Zoom is an evolution of the concept, and became possible as the image resolution of cameras increased. Nowadays, 4 and 5 megapixel image sizes are common, and this allows a smaller, but still useable section of the full resolution to be used without interpolation. With this system however, for the Smart Zoom to be available, the user must select an image size inferior to the camera's maximum image size.

With all cameras, when a smaller image size than the full resolution of a camera is selected, the image captured by the sensor, whatever that may be, is "downsized" by the camera to match the selected image size. The downsizing process can be thought of as the opposite of interpolation, the image size is reduced by extracting pixels (data) from the full size image resulting in the desired image size. In this case however, although data has been extracted from it, the image generally retains a sharp and detailed appearance.

It is this process theSmart Zoom takes advantage of, by using the full resolution of the sensor and cropping the central part of the image it captures.

As long as the image size is less than the full resolution of the sensor, the Smart Zoom can work from the full image, avoid any interpolation, and the attendant degradation of the image quality that the interpolation process entails.

Therefore, starting with a camera that offers a 5-megapixel resolution (a full resolution of 2592 x 1944), when the the camera is set to capture a 640 x 480 pixel image, the full size image is internally downsized to 640 x 480. If the optical zoom is used, up to its maximum magnification, the captured photo is downsized to 640 x 480. But, when the Smart Zoom is used, the difference between the selected image size (640 x 480) and the actual resolution of the sensor (2592 x 1944), allows capturing an image that seems to have been taken with an even longer lens, but is simply cropped and at most downsized a slight bit.

One could assume that this same principle holds true with all digital zooms. As long as the image size is set to a smaller size than the full resolution of which the sensor is capable, the camera will reduce the degree of interpolation, or avoid it altogether. However, such may not be the case. Just as likely, the camera will interpolate the digitally zoomed image, and then re-size it downwards to save it; in effect "blurring" the digitally zoomed image through interpolation first, and then "re-sharpening" it through the downsizing process. Not quite the same as a Smart Zoom.

Conclusions:

Until the arrival of the Smart Zoom, the Digital Zoom was probably the most misleading, and frankly, useless element found on a digital camera. As it was originally implemented, the digital zoom simply degraded the picture quality. Moreover, it was regularly used to boost the apparent capability of a camera, which only served to confuse those unfamiliar with its function. This is changing. Most newer cameras — with some exceptions — are not marketed with the digital zoom lumped in with the optical zoom, and others are adopting the Smart Zoom concept.

A few things to consider when buying a digital camera

2011-08-27T00:39:00.000-07:00

A few things to consider when buying a digital camera

This article is intended as a synopsis of desirable features to have on a digital camera, things that should be considered when selecting a camera.

We have purposefully left out some items for consideration: the ergonomic design of a camera; the type of viewfinder; the size and resolution of the LCD monitor; etc. Instead, we have tried to distill those things we judged to be the most important elements.

Resolution:
As of this writing, and excluding special application cameras, digital cameras are available with sensors that cover a range from 640 x 480 (307,200 pixels) up to 14 megapixel (14 million pixels). For most consumers though, the current economic limit is at 8 megapixel.

A word of caution when considering resolution, the true resolution of the sensor is what matters, meaning the number of pixels physically present on the sensor, and not the resolution of the image. If the image the camera produces is bigger than the number of pixels on the sensor, for instance the CCD is 3 megapixel but the image size is 6 megapixel, the image is interpolated.

Strictly speaking, the higher the resolution the greater the detail the camera is able to capture, meaning that an 8 megapixel image will always have more detail than a 1 megapixel image. Likewise, larger resolution images result in more detailed prints, and if desired, larger prints.

But, when the gap in resolution is not as large, such as is the case between 3.2 megapixel and 4 megapixel, other factors can tip the balance towards a camera with a lower resolution, and its photos may end up being more detailed than those of the higher resolution model.

One of the factors that can impact the amount of detail a camera captures is compression.

(Related articles: Why resolution matters; Resolution vs Image sharpness; Interpolation;How many megapixel do you need?)

Compression and image formats:
One of most important things to look for when purchasing a camera is the type and variety of image file formats it offers. The vast majority of images captured with digital cameras are stored in JPEG format. JPEG uses a lossy compression algorithm that reduces the colour hues of the image in order to reduce its file size therby lessening the time it takes to save it, and the space it takes up on the memory card.

The downside of the JPEG format is that if the compression applied to the image is too strong, the quality degrades visibly, and images become much less detailed than they should be. It is therefore critical to ensure that any camera offer a good selection of compression settings.

A camera should offer at least 3 image compression settings, and one of these should offer a limited compression, creating files that are no less than 1/4 to 1/6 the uncompressed file size.

If possible, an uncompressed format should also be available (TIFF) and/or a RAW format that simply stores the image captured by the sensor "as-is".

(Related article: Compression)

Lens:
Most compact digital cameras have an optical zoom lens — not to be confused with a digital zoom (see "Related articles below) — and zoom lenses should meet some basic minimums.

A lens should have a fairly bright maximum aperture — f2 or f2.8 — and should correct for distortion: barrel distortion at the wide angle end, pincushion distortion at the telephoto end and chromatic aberration.

If a long telephoto lens is under consideration, the maximum aperture available at the telephoto end should be checked. Lenses that have relatively small apertures at the maximum telephoto position may require a lot of ambient light to avoid camera shake. Alternatively, it may be advisable to look to a camera that offers a stabilized lens. Additionally, very long telephoto lens tend to produce a better image contrast when LD (Low Dispersion) glass is used in their construction.

Shutter speed range and noise reduction:
The shutter speed range of the camera should be checked. Cameras that have the combination of bright lenses and high shutter speed are better at stopping fast action. Similarly, cameras that are capable of long exposure times — at least 8 seconds — are able to capture photos at night. Ideally, the shutter speed range of the camera should extend to both fast and slow shutter speeds. Moreover, a camera able to capture long exposures should offer a noise reduction feature.

(Related articles: The effect of shutter speed on the image; Night Photography; Noise: what it is and when to expect it)

Shooting modes:
The availability of a good range of shooting modes is an important element of a camera. Users that want point and shoot simplicity should also look for cameras that provide a variety of Scene modes. Scene modes automatically set a number of shooting parameters for specific types of image types. While not all these modes are useful, a handful of basic scene modes can be very useful:

• Portrait	• Night Scene	• Landscape
• Sports	• Beach/Snow	• Sunset

For users that want the flexibility to experiment with the way the camera captures images, the more "hands-on" Aperture Priority, Shutter Priority and Manual modes should be available. Moreover, the ease of use of the modes — the way shutter speeds or apertures are adjusted — should be checked.

Burst (also called Sequential) shooting modes should also be part of the package. These modes are designed to capture a series of images quickly so as to overcome the shutter lag of the camera. While many cameras nowadays exhibit very little shutter lag, autofocus and metering still require a bit of time. Burst modes go a long to overcoming this by allowing the photographer to capture as the action unfolds.

From http://www.megapixel.net/html/articles/article-what.php 27/08/2011

• Portrait	• Night Scene	• Landscape
• Sports	• Beach/Snow	• Sunset

Five Ways Digital Cameras Beat Film

2011-08-27T00:27:00.000-07:00

Five Ways Digital Cameras Beat Film

By Charlie Sorrel

Film might not be dead, but it has been relegated to a niche category. In its place has risen the digital camera, a product so successful that it has set the popularity of amateur photography on fire in a way not seen since George Eastman launched his mass-market Brownie.

It’s not hard to see why. While it can be argued (and I have tried) that film cameras still have some advantages, the modern digicam is better in so many ways that the demise of film is no surprise at all. Here’s a list of five ways the digicam wins.

Cost

This is the biggest. While the actual camera itself might cost more than an equivalent analog box, once you have it, the running costs are almost zero. No trips to the chemist or lab to have film developed– heck, no film to buy. And although you have to recharge the batteries once in a while, the price is negligible.

This alone is good enough to get more people out snapping, but the close-to-zero running costs are probably the biggest factor in the modern surge in photography as a hobby. You can shoot as much as you like. No more rolls of film with Christmas at both ends and a few birthdays in the middle — today we can shoot 100 frames, keep the best and throw the others away. No wonder amateurs are getting better.

Instant Gratification

It’s called ‘chimping’ and it annoys the the hell out of some people. The act of glancing at the camera’s screen after each shot has some drawbacks – you might miss a shot; you’re not fully engaged in what you are photographing – but, along with the cavalier attitude to shooting brought by low prices, the instant review is probably the biggest contributor to quick learning.

With instant feedback, you can learn the consequences of your mistakes right away, and fix them. You don’t have to wait for two weeks to find out you left the lens cap on, and you don’t need to write down the camera’s settings to remind you of how you got a shot right.

In fact, so important is the instant playback that it has driven whole product categories into obsolescence: The light meter (and also flash meter) is now close to useless when you can check and adjust the exposure on the fly. And the LCD screen was arguably the last nail in Polaroid’s coffin, which was traditionally the pro’s version of chimping their shots.

Metadata

Simple, but so very useful, today its hard to imagine taking photos without embedded meta-data. You can search your photos by time taken, lens type used, even the auto-focus mode your camera chose for you. Add in a little of your own work – the names of the people in the pictures and – and auto geo-tagging (GPS location co-ordinates embedded in the photo file) and you can not only see just where you went wrong with a photograph, but find pretty much any picture, instantly.

Colonel Mustard, in the drawing room, with a bottle of whiskey on Christmas day? You got it!

Image Quality

There. I said it. This point will kick up a debate amongst the purists, just like vinyl vs CD, but the fact is that for almost everyone, the photos from a digital camera are better than they would get from film. Resolution has surpassed that available to film (on pro-cameras, the lenses are now the limiting factor) and with modern digicams the low-light noise has either almost disappeared or can be tweaked out later.

Be honest: most of us look at our pictures on a computer screen, so six-megapixels is plenty. Even when we printed our analog shots, we scarcely went above 6×4s. Even the last remaining advantage of film – a higher dynamic range – has been fixed by the likes of the Nikon D3. Add in the ability to change the ISO "film" speed on the fly instead of being stuck with the wrong film in the camera, and photographers have never been able to get such great pictures, with such consistency.

No Film

This might seem obvious, and it is also the reason behind the low cost of shooting digital, but not using film has other benefits. You can safely run your camera bag through airport X-Ray machines without fogging your images, memory cards hold a lot more pictures than a 36 exposure roll and, best of all, you can’t open the camera back and ruin the whole film with light.

Sure, you don’t get the range of specialist emulsions that film offered, but then, that’s what Photoshop is for.

What have we missed? Or what did we get wrong? Answers, as always, in the comments.

From http://www.wired.com/gadgetlab/2008/12/five-ways-digit/#more 27/08/2011

outstanding "prothusiast" D-SLR, solid upgrade from my D5000

2011-08-27T00:23:00.000-07:00

Outstanding "prothusiast" D-SLR, solid upgrade from my D5000

Paul Christensen

As a long-time owner of the Nikon D5000, and former owner of the Nikon D60, I was eager to purchase the D5100 after seeing the announcements and pre-reviews. Being one of the lucky ones to buy the D5100 with 18-55VR kit earlier this week, I've had a few days to play with this camera and can honestly say it's a solid upgrade to the D5000 I'm replacing, and should be on the short list of consideration for any
"prosumer" looking to purchase a D-SLR with outstanding image quality, performance, and low-light capability in a lightweight, compact (for an SLR) body. And, unlike the D5000, this D-SLR finally has a usable Live View and HD video capabilities both with continuous autofocus.

First of all, it's important to understand where the D5100 fits in Nikon's capabilities. It is considered a "high-end enthusiast" D-SLR which means that it shares the same image sensor as the high-end D7000 without some of the higher-end features. If you're like me, very few of the D7000's features justify its extra cost and weight. The D5100 offers nearly the same image quality as its bigger brother in a less-expensive, smaller package, while adding a few tricks the D7000 doesn't have including an articulating display that helps you frame hard-to-reach spots.

Compared to its lesser-priced but still excellent brother the D3100, the D5100 offers improved image quality, speed, and resolution, along with a higher-resolution articulating display. For me, this is the sweet spot in Nikon's consumer D-SLR offerings.

The 18-55VR (3x) f3.5-f5.6 kit lens provides surprisingly good performance and image quality, although you'll likely outgrow it quickly. I have uploaded a few sample images taken with the D5100 and 18-55VR to show its performance and surprisingly good bokeh (pattern of blurred background) in large-aperture and macro shots.

For lens upgrades that include an AF-S autofocus motor, if you don't mind changing lenses, the Nikon 55-200VR is an outstanding value with excellent image quality, or consider the Nikon 18-105VR (5.8x) lens included with the D7000. If you don't mind some distortion and image softness, the 18-200 VRII (18x) lens may be your perfect "walkabout" lens. For me, I bought the pricey but outstanding Nikon 16-85mm VRII. Don't forget the Nikon AF-S 35mm f1.8 (if you can find it).

Low-light performance is outstanding with this camera, and the level of detail captured by the D5100 is excellent, even at higher ISOs. You're best capturing in RAW or RAW+JPEG mode (three different JPEG compression levels are offered) if you need to go back and fine-tune exposure or other settings after the shot. Nikon also offers "Active D-Lighting" which is a highly effective method for improving dynamic range of a photo to equalize the difference between high and low-light areas of a photo.

Interestingly, the improvement in image quality compared to my D5000 isn't dramatic. Given the incredible improvement I saw when upgrading from my Nikon D60 to the D5000 perhaps I had unrealistic expectations for this new sensor. But in most image settings, even low light, the improvement is noticeable but subtle. That speaks more for the outstanding quality and low-light sensitivity of the D5000 sensor (which is shared with the D90) than it speaks against the D5100. With the D5100 you get higher resolution for improved cropping, and the 14-bit RAW images offer greater dynamic range for more flexibility after the shot is taken.

Speaking of RAW format, as with any new camera, there is a bit of a wait until updates are available for your favorite camera software. As of May 18th, Adobe, Apple, and Nikon have added support for the D5100 RAW files, so you can use Aperture, iPhoto, Nikon View NX2 (v2.1.1 and later), Nikon Capture NX2 (v2.2.7 and later), Lightroom 3 or Photoshop CS5 (via Adobe Camera RAW 6.4 or later). If you use other photo software or another platform, you may want to verify RAW support for the D5100.

Compared to my D5000, Nikon has gone back and addressed most of my concerns on ergonomics and performance:
- camera body is roughly 10% smaller and 10% lighter
- 16.2 megapixel CMOS DX-format image sensor (shared with D7000) captures 14-bit RAW images and offers +1fs greater low-light sensitivity
- ISO 100-6400 range with expansion to 25,600 ISO (D5000 minimum is 200 and expansion to 12,300)
- high resolution (920k pixel) display for greater detail in image previews (although I had to bump up the default brightness one notch for accuracy)
- side-mounted articulating display no longer interferes with tripod (the D5000 display is inconveniently hinged at the bottom)
- dramatically improved (now usable!) LiveView mode with continuous autofocus even in HD video mode (more on that later)
- full HD 1080p movie capture without the "jelly effect", in more standard H.264 mode up to 22 min (D5000 is AVI format 720p up to 5min)
- slightly better control position (LiveView is now a rocker switch on the mode dial, Video Record is just behind and to the left of the shutter release)
- significantly quieter shutter release (plus, a "Quiet Mode" is available although hardly necessary)
- faster performance (4 frames per second)
- SDXC compliant supports higher capacity cards
- remote control sensor on rear now in addition to front-mounted sensor
- improved battery life, and an improved battery release
- battery charger now has built-in collapsable plug instead of requiring separate power cord
- MUCH better eyecap design no longer comes off in my small Nikon camera bag; also an improved diopter (eyeglass) control
- additional in-camera editing capabilities, including ability to trim video
- new "gimmick" special effects: in-camera HDR, selective color, night vision, etc

Let's start with the display - moving the hinge to the side not only makes the articulating display usable with a tripod, it makes the camera body shorter, so that it matches the height of most popular Nikon DX-format lenses and no longer leans forward when set down on a table as the D5000 did. It makes a surprising improvement in shooting comfort also. Nikon has improved the rubberized grip of the body and the thumb rest in the rear, although some have said that the grip is a bit shallow for larger hands. For my average-sized hands it is very comfortable.

The improved control placement is mostly welcome as well. LiveView is now a spring-release rocker on the side of the Mode Dial (VERY handy) and the video record button is also now on the top of the body, in front of the mode dial and behind the shutter release. What I didn't care for is the placement of the rear camera buttons, which now all shift above and to the right of the display to accommodate the left-mount hinge. What I don't like is that the "i" button (used to display and change shooting info) is too far away from the 4-way mode switch, so changing default shooting settings is a bit more of a stretch on my thumb. On playback, the delete button is just to the right of the Zoom buttons, instead of being far away like it should be. I didn't find myself accidentally deleting photos, but I'd rather have had a button closer by that I use more frequently (like the Menu button?)

What has dramatically improved from the D5000 is LiveView performance and HD video capture. Neither are perfect, but compared to my D5000 both are quite usable in the D5100. In LiveView mode, the D5100 tracks faces and subjects quickly and accurately, although still nowhere near fast enough for sports events or that "quick shot" like you might be used to with a compact camera. On my D5100, LiveView autofocus typically took half a second in lower-light conditions, which is no match for the viewfinder, but a huge improvement from the D5000.

Video capture is another notable improvement in the D5100, capturing single videos up to 22 minutes of 1080p HD (if you have the SD card capacity), in H.264 format, with continuous autofocus. Gone is the "jelly effect" of the D5000 when you quickly panned horizontally and the video appeared to bend. In theory, the continuous autofocus sounds like a great improvement for video capture, but in practice I found it slow to react (especially in low-light situations). Too often I found the camera "searching" for the correct focus, even with the (optional) Nikon 35mm F1.8 AF-S lens. It was so distracting that I ended up disabling autofocus and learning how to manually adjust focus as I moved from subject to subject. Also disappointing is that like the D5000, the built-in microphone is monoral. For stereo sound, you must buy the (forthcoming) ME-1 external microphone. Overall, the video capabilities are promising, especially at 1080p, but I am more satisfied with the native 720pHD stereo video captured from my Canon S95.

Rounding out the list of improvements and new features of the D5100 are the new "special effects", including the first in-camera HDR mode for any Nikon D-SLR. In practice, while there may be edge cases for these effects, I am not particularly impressed with any of them, including HDR. First of all, you cannot capture RAW with any of the effects. For HDR, there are further limitations (can only be used in P-S-A-M modes, not auto, no flash, etc). When you can get HDR mode to work, it can only be enabled one shot at a time, and then you have to go back to the menus to turn it on. Luckily, you can assign HDR mode to the Fn menu button. HDR mode takes two quick shots for each shutter press and then combines them in-camera to create a single JPEG. You can specify the exposure difference (Auto, 1EV, 2EV, 3EV) and level of "smoothing" (Low, Normal, High) between the captured images. I took a number of high-contrast shots with HDR enabled and honestly couldn't see a difference, although I'm still going to try. If there is any good news, it's that Nikon has chosen a fairly conservative / realistic HDR algorithm as opposed to an "eye-popping" but over-processed result.

In summary, I'm quite happy with the D5100. It provides the optimal balance of top image quality (even in low light), lightweight and compact (for a D-SLR) body, articulating display (the only D-SLR from Nikon to have this), and HD video (not perfect) that can leverage the outstanding collection of Nikon lenses (understanding that only AF-S lenses will autofocus).

Notable comparison with the higher-end D7000:
- same 16.2megapixel image sensor with 14-bit RAW image capture for outstanding dynamic range, low-light performance, and detail
- ruggedized plastic body lacks weather seal (it's also smaller and lighter weight)
- no builtin focus motor for older lenses (you'll need to buy an AF-S lens if you want autofocus)
- fewer autofocus zones (11 vs 39) and lower-resolution matrix meter
- pentamirror viewfinder (smaller, not as bright, 95% coverage) vs pentaprism viewfinder (100% coverage)
- no flash commander mode (unless you buy an external flash with TTL triggering)
- slower continuous performance (4 vs 6fps)
- 1 SD card slot instead of 2
- no top-mounted LCD display
- fewer dedicated controls for advanced settings (you must use the menu system more frequently)

Notable comparison with the lower-end D3100:
- higher resolution 16.2megapixel sensor with 14-bit depth
- high resolution (920k pixel vs 230k) display, articulating for hard- to-view shots
- higher low-light sensitivity
- faster performance (4fps vs 3fps)
- better battery performance (660 vs 550 images on the same EN-EL14 battery
- slightly larger and heavier body

From http://www.amazon.com/Nikon-D5100-Digital-18-55mm-3-5-5-6/dp/B004V4IWKG/ref=zg_bs_502394_10 27/08/2011

Canon EOS Rebel T3i 18 MP CMOS Digital SLR

2011-08-27T00:13:00.000-07:00

Canon EOS Rebel T3i 18 MP CMOS Digital SLR

Choosing between the T3i, T2i, 60D and 7D

The Canon Rebel T3i takes the consumer level dSLR a couple steps closer to the mid-level Canon 60D with the addition of the rotating rear LCD screen, remote flash firing, and in-camera processing features. The already highly competent, older Rebel T2i already shared many important features with the 60D (and even features of the semi-pro 7D) including the 18 MP sensor, 63-zone exposure metering system, high ISO performance, HD movie capabilities, and Digic 4 image processor. With these new upgrades, it might make it even more difficult to choose between them. But there are some important differences.

If you are considering the Rebel T3i vs T2i, the Rebel T3i is replacing the T2i. Since both cameras share the same 18 megapixel sensor and Digic 4 processor, both the T2i and T3i will create images with exactly the same image quality, produce the same low light/ high ISO performance, shoot at 3.7 frames per second, and have nearly the same size and build quality. They are both offered with the same 18-55mm kit lens (with some minor cosmetic differences on the new T3i kit lens). The T3i is very slightly larger and heavier due to the addition of the rotating rear LCD monitor. And that is one of the biggest differences between the two cameras. Do you want and need a vari-angle rear screen or not? The other major difference is the ability of the T3i to remotely control multiple off-camera flashes. Like the 60D and 7D, you can use the built-in flash of the T3i to trigger other Canon Speedlites. Some other minor additions to the T3i include the Scene Intelligent Auto Mode, which is a feature borrowed from point and shoot cameras. When in Auto mode, the T3i will make a determination of what type of scene you are shooting - close-up, portrait, landscape, etc. - and automatically configure the camera settings accordingly. However, if you want to use a powerful and costly digital SLR as a point and shoot, you should probably save the money and just buy a nice, high quality point and shoot like the Canon S95. Other additional but not essential upgrades include the in-camera processing Creative Filters, and the ability to choose different image size ratios and to rate your images. (Helpful hint: press the Q Button while in image playback and you can access features like rating, rotating, and Creative Filters.) There is also a marginally helpful Feature Guide which gives brief descriptions of various settings and some additional video features like Video Snapshot, which you can use to shoot short video clips that are automatically joined together into a video, with music.

Canon Rebel T3i vs. 60D vs. 7D
Sensor and Image Quality: All three cameras share a very similar sensor and 18 megapixels, and so their image quality will be virtually the same. All are capable of taking professional quality images.

Exposure Metering: The three cameras all share the latest 63-zone, dual-layer exposure metering system and 4 metering modes. That means they will all determine the exposure virtually identically and enable you to take properly exposed photos in most every situation, including difficult back-lit scenes. The size of the areas metered for Partial and Spot metering vary slightly between the cameras, but that isn't anything critical.

Autofocus: The T3i shares a similar autofocus system to the 60D, with 9 focus points and three auto focusing modes. However the 9 AF points of the 60D are more sensitive than those of the T3i: all are cross-type in the 60D, only the center is cross-type in the T3i. The 60D autofocus system is much less complex than the sophisticated AF system of the 7D with its 19 AF point system and its additional Zone, Spot, and Expansion focus modes. These various modes address how you want to deal with and group the numerous AF points. Plus the custom settings of the 7D allow one to customize how the AF system works - how it tracks subjects, how it deals with objects that come between you and your initial subject, how quickly it responds to these changes of possible subjects that are at different distances from you, etc. However, if you are not an avid sports photographer, a wildlife shooter, or someone who understands, needs, and will use the elaborate features of the 7D AF system, then this shouldn't sway you.

Construction: As you can probably figure out from the prices, each camera is not built the same. The T3i has relatively strong construction of a stainless steel frame with polycarbonate body. The 60D has a stronger and lighter aluminum frame and polycarbonate body, but not as strong as the 7D's magnesium alloy construction. The 60D also has some amount of weather sealing - more than the T3i, less than the 7D. But for most users, including even those using the camera daily or in travel situations, the construction of any of these cameras is far more than good enough, strong enough, and durable enough.

ISO: Since they all share a very similar sensor, the ISO sensitivity and performance at high ISO settings is virtually the same for these three cameras. But don't take my word for it, don't be swayed by pixel peepers on forums, instead check out the camera sensor tests at dxomark to verify this. As you can see, they all share the exact same overall score, and show very similar performance.

Controls: As with construction, the buttons and controls vary with these cameras. Unlike the T3i, the 60D and 7D have nearly every control an advanced photographer needs on the exterior of the camera and they also have the top LCD panel and rear Quick Control Dial that are not on the T3i. With all the cameras, any controls can also be easily accessed with the Q Button and Q Menu or in the other menus on the rear LCD monitor. The top buttons of the 60D set only one setting each, so this is less complicated than the multiple-setting buttons of the 7D. Canon has removed the white balance (WB) button on the 60D that the 7D has, but that isn't a big deal - use the Q Menu. Another change on the 60D is that the Multi-controller has been moved from the thumb joystick like the 7D and 50D and placed in the middle of the rear Quick-control dial. This doesn't change how it functions, and should just be a matter of getting used to the difference. If you plan on using your camera on Auto or Program most of the time, then the controls of the T3i are more than sufficient for your needs. If you work in Av, Tv, or M modes and need quicker and more direct access to your controls and the additional top LCD screen to view and change your current settings, then you need to consider the 60D or 7D over the T3i.

Menus and Custom Functions: These allow for greater control over customizing how the camera functions. The T3i has less Menu and Custom Function setting options than the 60D, and the 7D has yet a few more than the 60D. These settings enable you to customize the operation, function, and controls to work how you want them to, including things like exposure increments, peripheral illuminations correction for lenses (fixes dark corners), tweaking how the autofocus system operates, setting more precise white balance settings, and customizing which button does what. There are ebooks such as my Canon T3i Experience - The Still Photographer's Guide to Operation and Image Creation With the Canon Rebel T3i / EOS 600D and Your World 60D - The Photographer's Guide to Operation and Image Creation with the Canon 60D which walk you through all of the Menu settings and Custom Function settings so that you can set up your camera to work best for how you photograph, and also begin to learn to master all the advanced features, settings, and controls of these powerful dSLR camera.

Wireless Flash: Like the 7D and 60D, the T3i incorporates wireless flash triggering. This allows you to trigger multiple off camera flashes at different output levels. The T2i does not have this feature.

Articulating LCD Screen: The big new feature that the 60D and T3i have that the 7D and T2i do not is the articulating rear LCD screen. This may prove useful for videographers, as well as for setting up compositions while the camera is on a tripod, for macro use, or for using it from unusually low or high vantage points. Some users will be able to avoid buying an expensive angle finder because of this feature. There is also an electronic level in the 7D and 60D, visible in the viewfinder, rear LCD, or top LCD.

Viewfinder: The T3i has a pentamirror viewfinder with 95% coverage of the actual resulting image. The 60D has a large, bright pentaprism viewfinder with 96% coverage, not quite as nice as the nearly 100% view of the 7D pentaprism.

Processor: The T3i shares the same Digic 4 processor as the 60D. The 7D has dual Digic 4 processors. However, if you don't need to shoot dozens of continuous images, you probably won't notice any processing speed issues.

Continuous Shooting Speed: The T3i can shoot 3.7 frames per second. The 7D can shoot a blazing 8 frames per second, in which the photos barely change from frame to frame. The 60D can shoot a respectable 5.3 fps which is actually a more useful rate. If you need the extremely high fps for sports, wildlife, or other action shooting, get the 7D. If not, don't be swayed by this excessive feature.

Memory Card: The T3i and 60D use the SD memory card. The 7D uses the CF card.

Battery: The T3i and T2i use the smaller LP-E8 battery with less capacity than the LP-E6 battery used by the 60D and 7D.

Size and Weight: The T3i is smaller and lighter than the 60D, which in turn is smaller and lighter than the 7D. Go to a store and hold them to get a better feel for their size, weight, and feel. The 60D and 7D "feel" like the more substantial cameras that they are. A nice improvement of the T3i is that its hand grip area has been modified, and has a different feel than that of the T2i - the area where the thumb rests is contoured differently and has a nice channel for the thumb, which allows for a much more secure one-hand-grip of the camera.

AF Microadjustment: The 7D has this feature, the 60D and T3i and T2i do not. This allows you to adjust the focus of each of your lenses in case any of them are slightly front-focusing or back-focusing.

Locking Mode Dial: This is a new feature for a Canon dSLR, only on the 60D, that keeps the Mode dial from accidentally rotating. A nice touch.

Full HD video: Of course they all offer this capability. Note that this is not video for your kids' parties and soccer games. It does not have continuous autofocus while shooting, as a camcorder does. It is not designed for that kind of use, but rather for serious videographers who typically manually focus. You can adjust autofocus while shooting by pressing the shutter button or the AF button, but it may have a less than desired looking result and unless you are using an external microphone, the autofocusing sound will be picked up. The T3i has the digital zoom feature in video, which allows for nice smooth zooms while filming.

Flash Sync: the 60D and T3i do not have a PC sync flash socket to plug in PC sync cords for off camera flash use. The 7D has this. However, they all offer wireless remote flash capability with the built in flash as a commander.

Ease of operation: While beginners may find all the buttons, controls, and menus of any dSLR difficult and confusing at first, the menus and controls of the T3i and T2i are pretty basic and simple to learn for a dedicated user. The additional controls and menus of the 7D and 60D are all quite intelligently designed, intuitive, and straightforward for the more advanced user. Again, have a look at helpful guides such as my Canon T3i Experience - The Still Photographer's Guide to Operation and Image Creation With the Canon Rebel T3i / EOS 600D and Your World 60D - The Photographer's Guide to Operation and Image Creation with the Canon 60D to begin to learn to master all the advanced features, settings, and controls of these powerful dSLR cameras.

From http://www.amazon.com/Canon-T3i-Digital-Imaging-18-55mm/dp/B004J3V90Y/ref=zg_bs_502394_3 27/08/2011

Digital Cameras: The Basics

2011-08-24T07:03:00.000-07:00

Digital Cameras: The Basics
Instructor: Karen Douglas

What is a Digital Camera?
Digital cameras allow you to take photographs (and some digital cameras will take videos) without
the need for film. They use sensors that convert light information from the photographed scene
into a digital image. Each digital image is composed of many tiny pixels. In a graphic image, a
pixel, which is short for “Picture Element,” is a single point in a graphic image. When
discussing digital cameras, resolution can be defined as the number of pixels in an image. A
megapixel is one million pixels. Millions of pixels are combined to form one picture. Your
photos are stored on your camera’s memory card as a file. The larger (in file size) your
memory card is the more photos you can take at one time.

Some advantages of using digital camera versus traditional cameras.
1. No need to purchase film.
2. You can preview your images and decide which ones to edit, delete or print.
3. Share your digital photos online with family and friends.
4. If you own a photo printer, you can print your own
photos at your leisure.
5. You can organize and file your photos on your computer or burn to a CD for later use.

What are some Determining Factors to Consider when Purchasing a Digital Camera?

• Megapixels - If you want to take crisp photos that range from 4 x 6 up to 5 x 7 consider
purchasing a camera with at least 4 MP (megapixels) and for an 8 x 10, you will need
at least 7-8 MP. For larger prints, speak to a professional photographer to determine the best
camera for your needs.
• Size, shape and weight - It is recommend that you should always see the camera you wish to
purchase in person. That way, you can hold the camera to see how it fits in your hand, and
determine if the weight and size is appropriate for your use.
• Optical versus Digital Zoom - Digital cameras usually offer both optical and digital zoom.
You will produce better quality photos by using your optical zoom versus the digital zoom.
Try to buy a camera with more optical zoom options. The higher the number for the optical
zoom, the more powerful lens (for zooming) you will own.
• Price - The price can vary greatly. Determine which features are most important to you and
compare various brands. Refer to websites that have professionals who review digital
cameras. One example would be www.cnet.com
• Battery type - Consider purchasing a camera that uses a rechargeable battery.
• Manual and/or Auto Controls - Many digital cameras are very basic point and shoot
cameras. If you want more controls such as ISO or shutter speed, consider purchasing a
digital camera with manual controls as well.
• Software limitations or specifications - Before you purchase a camera, make sure it will be
compatible with your existing computer hardware and software.
• Ease of Photo transfer - Inquire about how the camera will transfer the photos to your
computer. You may need to purchase an additional USB cable or even a card reader.
• Memory Card - Most cameras come with a small memory card (such as 30 MB). You may
want to consider purchasing a larger card (1 GB) so that you can take more photos at one time
without having to stop and download the photos to your computer on a regular basis.

How do I Transfer Images from my Camera to my Computer?
The newer cameras on the market today use a USB cable which will connect to a USB
port on your computer. Follow your camera instructions for the exact steps for
connecting your camera to your computer. Most cameras come with software that will
assist you with downloading and editing your images. This software will usually
recognize when your camera is connected, and will typically open automatically. You
will be able to choose which images you wish to download by first viewing them on
your monitor.
Another option for downloading your images would be to purchase a card reader. This
device will allow you to place your flash memory card from your camera into the card reader. The card reader will
connect to your computer by using a USB port and will read your camera’s memory card. Some computers have a
built-in card reader. If you are unsure about whether you need to purchase an external card reader, please consult
with a computer technician.
Once you have downloaded your images to your computer, you can either print or email your images. If you decide
to archive your photos, you may want to create separate folders for each event (such as “Tammy’s birthday”, or
“summer vacation 2007”) and save to your hard drive. You could also save to an external storage device like a travel
drive or burn to a CD. Before you print or email your photos, you want to edit them by using image editing software.

What is Photo Editing Software?
Image editing software will allow you to change or manipulate your photos in several different ways. They will
usually allow you to lighten or darken a photo, rotate it, trim or crop out certain areas, adjust the contrast, remove red
eye and more. As mentioned before, most newer cameras come with some image editing software. Before you
purchase your camera, make sure its software is compatible with your system

How Would I use a Photo Sharing Web Site?
How do I Transfer Images from my Camera to my Computer?
The newer cameras on the market today use a USB cable which will connect to a USB
port on your computer. Follow your camera instructions for the exact steps for
connecting your camera to your computer. Most cameras come with software that will
assist you with downloading and editing your images. This software will usually
recognize when your camera is connected, and will typically open automatically. You
will be able to choose which images you wish to download by first viewing them on
your monitor.
Another option for downloading your images would be to purchase a card reader. This
device will allow you to place your flash memory card from your camera into the card reader. The card reader will
connect to your computer by using a USB port and will read your camera’s memory card. Some computers have a
built-in card reader. If you are unsure about whether you need to purchase an external card reader, please consult
with a computer technician.
Once you have downloaded your images to your computer, you can either print or email your images. If you decide
to archive your photos, you may want to create separate folders for each event (such as “Tammy’s birthday”, or
“summer vacation 2007”) and save to your hard drive. You could also save to an external storage device like a travel
drive or burn to a CD. Before you print or email your photos, you want to edit them by using image editing software.
Another option you may want to consider for sharing your photos would be to use an online
photo sharing site. These allow you to upload and save your photos so that family and friends
can view your photos from any computer with Internet access. These web sites provide you
with free storage and sharing.

What is the Difference between Pixels per Inch and Dots per Inch?
When we discuss digital images, the term ppi (pixels per inch)
primarily is referring to print quality not video (monitor) quality. Each
digital image is composed of thousands or maybe millions of pixels
(little squares of colors). See the enlargement of the parrot’s eye in the
sample photo to the right. The entire photo is composed of tiny square
pixels. The more megapixels your camera has, the more crisp and
clear your photos will be when printed in a larger format.
The term dpi (dots per inch) refers to how many dots a printer uses to recreate a single pixel
from your digital image. This refers to a printer property. If you used a 300ppi print setting
with a 2880 dpi printer, it would use 9.3 tiny dots to represent each pixel in your digital photo.
If you used a 240 ppi setting, the same printer would need to use 12 dots to represent each pixel.

What Settings Should I Use to Print My Photos?

If you have an image that is 800 pixels tall x 1200 pixels wide, and you print it with
a setting of 200 pixels per inch, your printed image will be 4 x 6. If you print that
same image with a setting of 300 ppi, your printed image will be 2.6 x 4. Even
though your image will be smaller, it will be of a higher quality. So, if you want a
quality 4 x 6 print, with a setting of 300 ppi, make sure you set your camera’s
image quality to 1200 x 1800 pixels prior to taking the photo. For a print size of 5 x
7, set your image size to 1500 x 2100 or something close to that setting before you
take your photo. For a print size of 8 x 10, set your image size to 2400 x 3000 (see
your camera instructions for specific settings). Remember that your camera may
come with certain preset pixel size settings. If this is the case, get as close as
possible to the settings above for the correct print size results. Keep in mind that the larger your image size is per
photo, the more file space it will need on your memory card. So, the larger the file size per photo, the less photos you
can save on your memory card at one time. If you have a 1 GB memory card in your camera, you can fit 500 individual photos that are 2 MB each. Don’t forget that you can always take your images and have them printed for you
directly from your memory card at a professional photo lab, a local photo kiosk or an online print website.

What Settings Should I Use to Email or Save My Images to the Web?

If you know your intent will be to save an image to a web site or to email an image
and you never intend to print the image, set your image resolution on a lower
setting. Remember that once you take a photo at a low pixel size, you can’t enlarge
the image size later to print a 4 x 6 photo. Well, technically you can, but it will
produce a very pixilated and blurry print.
The smaller the file size, the more images you can fit on your memory card. JPEG
is the preferred file format for saving photos to be emailed or saving to the Web.
To email a picture that is 5 x 7, you will want to change your camera settings to 360
x 504 pixels or for a 4 x 6, set your image size to 288 x 432 pixels before you take
your photo (see your camera instructions).

In Addition to my Camera, What else Should I Consider Purchasing?
• As mentioned before, most new digital cameras come with a small memory card.
If you want to be able to save many images and videos (if your camera has a video
option), then consider purchasing a memory card with one or two gigabytes
(1 or 2GB).
• In order to save files on a portable storage device, you need to be aware of the
file size of your images. Several photos can be saved to one floppy if the images
have a small file size. One floppy will hold up to 1.4MB of files. If you want to
save many photos or larger image files, please consider learning how to burn CD’s
or purchase a USB travel drive.
• If you will need to download your photos from your camera to another computer (other than your own computer), you may want to purchase a portable memory card reader. This device will connect to the computer’s USB port. Even though your friend’s home computer will not have the software from your camera
installed, you can use your memory card reader to install your photos from your camera to their computer.
• If you will be using an inkjet printer to print your new photos, then you will need to purchase some photo
quality paper. The best results will come from premium professional grade gloss paper.
• To protect your camera from bumps and scratches, you may want to purchase a camera bag. Some are made
to fit securely to your belt so that transporting the camera is very easy.
• A tripod is a device that holds your camera steady while you take a portrait. Your camera mounts to the
tripod and can easily be assembled for a quick photo. It is also a great way to take a photo of you with your
friends in case no one else is around to take the picture.

What are Some Techniques for Taking Better Photos?
• Remember to always hold the camera as still as possible. Brace your elbows into
your side for a more steady shot.
• When shooting outside, make sure the subject is not looking into the sun and
remember not to point your camera toward the sun.
• As you compose your shot, always pay attention to the background. Many
unsuspecting subjects have disappointing photos with mysterious “trees” or “poles” that
appear to be growing from their head! Try to move your subject so that the background
is appropriate and flattering.
• Another advantage of using a digital camera is that you can take “practice” shots. Take a photo and allow your
subject to see the photo. If it is an unsatisfactory picture, then just delete it and try taking another one.
• Learn how to take quality photos. See the following page for a list of books describing proper photo composition. Know when to take close up photos to capture the moment. Learn more about panoramic and macro shots
as well. Enjoy learning about your camera and all the possibilities you have to produce quality photos!

From http://www.clarke.public.lib.ga.us/services/digitalcamerabasics.pdf 24/08/2011

Digital Cameras - A beginner's guide

2011-08-24T00:13:00.000-07:00

Digital Cameras - A beginner's guide

by Bob Atkins

Digital Camera Basics - A primer

Digital cameras are confusing to a lot of new users. In this basic guide to digital camera technology we hope to try to give digital beginners at least some basis to use in deciding which digital camera is appropriate for them. When shopping for a digital camera it's at least good to know what the basic terms like white balance, pixel, ppi and dpi mean and how they affect image and print quality. It's also important to know the difference between things like optical zoom and digital zoom as well as the advantages and disadvantages between storage formats such as Compact Flash (CF), Microdrives, Sony Memory Stick, Secure Digital (SD), Multimedia and camera interface technologies such as USB 1.1, USB 2.0 and Firewire IEEE 1394.

Pixels

A pixel is a contraction if the term PIcture ELement. Digital images are made up of small squares, just like a tile mosaic on your kitchen or bathroom wall. Though a digital photograph looks smooth and continuous just like a regular photograph, it's actually composed of millions of tiny squares as shown below.

On the left the full image, on the right the area in the red square magnified to show individual pixels

Each pixel in the image has a numerical value of between 0 and 255 and is made up of three color channels. So for example a pixel could be 37-red, 76-green and 125-blue and it would then look like this . If it was 162-red, 27-green and 12-blue, it would look like this . There are over 16 million possible combinations using this scheme and each one represents a different color. Computer savvy readers will note that each color in this scheme can be represented by an 8-bit number (byte), so the color of each pixel is defined by three color bytes. This scheme can be expanded, for example to use 16-bits (two 8-bit bytes) for each color. Images using three 8-bit values are sometimes called 24-bit color images. Images using three 12-bit values for color definition are called 36-bit color images, and those using three 16-bit values are called 48-bit color images.

Pixel Count

One of the main ways that manufacturers categorize their digital cameras is in terms of pixel count. What this is is the number of individual pixels that go into making each image. Today this number varies between 1 million (1 Megapixel) to around 14 million (14 Megapixels). A million pixels is abbreviated to MP, so a 1MP camera has 1 million pixels and a 3MP camera has 3 million pixels. Currently most popular consumer digital cameras have between 2MP and 5MP. A 3MP camera can make excellent 4"x6" prints and very good 5"x7" prints. If you intend to make lots of 8"x10" prints, then perhaps a 4MP or 5MP camera would be a better choice. Sometimes two numbers are given, total pixels and effective pixels. Total pixels count every pixel on the sensor surface. Usually the very edge pixels aren't used in the final image. Effective pixels are the number of pixels actually used in the image after the edge pixels have been dropped.

	3MP	4MP	5MP
Largest Image (typical)	2048 x 1536	2272 x 1712	2592 x 1944
Print size at 320dpi	6.5" x 4.8"	7.1" x 5.4"	8.1" x 6.1"
Print size at 240dpi	8.5" x 6.4"	9.5" x 7.1"	10.8" x 8.1"

Typical maximum image size vs. nominal Pixel Count. See below for comments on dpi and print size

Aspect Ratio

The aspect ratio of a camera is the ratio of the length of the sides of the images. For example, a traditional 35mm film frame is approximately 36mm wide and 24mm HIGH. This has an aspect ratio of 36:24, which can equally well be expressed as 3:2. Some digicams use the same aspect ratio for their digital images. For example most digital SLR (single lens reflex) cameras have a 3:2 aspect ratio. However, video monitors typically use a 4:3 aspect ratio. For example a monitor with a 800x600 display has a 4:3 aspect ratio. With this in mind, most consumer level digicams use a 4:3 aspect ratio for their images.

Sensor Size

The size of the digital sensor element (which is equivalent to the size of the negative for film cameras) is pretty small in all consumer digicams - typically around the size of a fingernail (and a small fingernail at that!). As I said above, a 35mm film frame is 24mm high by 36mm wide but most digital cameras use sensors very much smaller than this. Here are some typical digicam sensor sizes. The "name" of the sensor is based on specification for old TV tubes used in the 1950s. Nobody is quite sure why it's being used for modern digital sensors since the "sizes" don't really relate in any consistent way to the actual physical size of the sensor. However these names are widely used, so it's best to know what they are. They are often listed in digital camera spec sheets.

Relative size of various digital camera sensors	"Name"	Aspect Ratio	Width (mm)	Height (mm)
	1/3.6"	4:3	4.0	3.0
	1/3.2"	4:3	4.5	3.4
	1/3"	4:3	4.8	3.6
	1/2.7"	4:3	5.3	4.0
	1/2"	4:3	6.4	4.8
	1/1.8"	4:3	7.2	5.3
	2/3"	4:3	8.8	6.6
	1"	4:3	12.8	9.6
	4/3"	4:3	18.0	13.5
	EOS 10D	3:2	22.0	15.0

Most of the current small 5MP digital cameras use 1/1.8" sensors which are about 7mm x 5mm. They have an area 25x smaller than 35mm film and about 9.5x smaller than a small sensor digital SLR like the Canon EOS 10D. You might wonder why sensor size matters and that's a pretty complex issue. The bottom line is that, for a given pixel count, the larger the sensor (and hence the larger the area of the individual pixels) the better the image quality and the lower the noise level. While large sensor cameras like the EOS 10D can operate at the equivalent of ISO 3200 (though the image does get noisy), many consumer digicams with small sensors cannot operate above ISO 400 before the noise becomes excessive. For a full treatment why all this is so, see my article here on photo net titled SIZE MATTERS

Another factor in quality here is that small sensors tend to be of a different type than large sensors. Small sensors, and the sensors used on all consumer digital cameras, use a scheme which can read the data from the sensor in real time using a scheme called "interline transfer" and the CCD electronics control exposure rather than a mechanical shutter. Large sensors used on more expensive Digital SLRs are often of a different design known as full frame - which doesn't refer to their size, but their design - and which require the use of a mechanical shutter. They don't read out and the display the data in real time, only after the exposure so they can't give real time LCD displays or record video. The advantage of this scheme is that the whole pixel area can be used to capture light while interline transfer CCDs use part of each pixels to store charge. Since smaller pixel areas generate more noise and interline transfer CCDs are not only smaller to start with but use some of their pixel area for charge storage, their noise level is significantly higher. So the smaller interline transfer sensors in consumer digital cameras yield lower quality images than those used in higher end DSLRs, they can do more "tricks" like recording video clips and giving a live image display on their LCD screen. The lack of a mechanical shutter also makes the cameras cheaper and simplifies construction.

Small sensors mean that short focal length lenses are needed to give the same field of view as cameras using larger sensors or 35mm film. So, for example, a typical consumer digicam may need a 7mm lens to give the same view as you would get using a 35mm focal length lens on a 35mm camera. This has consequences on depth of field and means that most consumer digicams have a vary large depth of field. Great if you want everything in focus, not so great if you want a blurred background. This is covered in detail in my article here titled DIGITAL DEPTH OF FIELD

White Balance

With film you can buy "daylight balanced film" for shooting outdoors or "tungsten balanced film" for shooting indoors under normal domestic lighting (not fluorescents!). If you use daylight film under tungsten light the images will be very yellow. If you use tungsten film in daylight the images will be very blue. With film you have to correct for the "color temperature" of the light using filters or by the right choice of film.

With digital you can pick your white balance to suit your light source, so that white looks white, not yellow or blue. Normally there is an automatic setting and the camera decides what white balance setting to use. However if you know what your light source is you can usually set the camera to it and this may give better results. Most digital cameras have settings for sunlight, shade, electronic flash, fluorescent lighting and tungsten lighting. Some have a manual or custom setting where you point the camera at a white card and let the camera figure out what setting to use to make it white.

Sensitivity

Sensitivity settings on digital cameras are the equivalent of ISO ratings on film. Just about every digital camera will have settings with a sensitivity equivalent to ISO 100 film and ISO 200 film. Many will have an ISO 400 setting, but above that the images from cameras with small sensors gets pretty noisy. The more expensive digital SLRs with much larger sensors have much higher sensitivity settings. At ISO 400 they are virtually noise free and some can go as high as ISO 3200 or even ISO 6400! Very few cameras have ISO setting lower than ISO 100 because noise levels are so low at ISO 100 there would be no real advantage in a slower setting. Quite a few digital cameras have an "auto" ISO setting, where the camera will pick from ISO 100, ISO 200 and sometimes ISO 400, depending on the light level and the mode in which the camera is operating.

Digital Zoom and Optical Zoom

Most cameras have both optical zoom and digital zoom. Optical zoom works just like a zoom lens on a film camera. The lens changes focal length and magnification as it is zoomed. Image quality stays high throughout the zoom range. Digital zoom simply crops the image to a smaller size, then enlarges the cropped portion to fill the frame again. Digital zoom results in a significant loss of quality as is clear from the examples below. It's pretty much a last resort, and if you don't have it in camera, you can do a similar job using almost any image editing program.

Comparison of optical zoom and digital zoom

JPEG, TIFF and RAW

The size of the digital file corresponding to the image which the camera produces depends on the pixel count. In most consumer digicams each pixel generates 3 bytes of data (so called "8-bit data"). One for red, one for green and one for blue. This means that a 3MP camera, which has 3 million pixels, generates 9 million bytes of data, or 9MB (megabytes). A few cameras can generate extra data for extra quality, and some of these cameras generate files which correspond to 2 bytes of data for each color ("16-bit"), so a 3MP camera which is capable of generating 16-bit data will produce an 18MB image file.

Now these files are pretty big and they can be compressed quite a lot without a significant drop in quality. This is where JPEG (Joint Photo Experts Group) comes in. JPEG is an algorithm designed to work with continuous tone photographic images) which takes image data and compresses it in a lossy manner (this means you do lose some information). The more you compress, the smaller the file but the more information you lose. However, you can reduce file size by a factor of 10 or so and still get a very high quality image, just about as good as the uncompressed image for most purposes. You can reduce the file size by a factor of 40 - or even more - but the image starts to look really bad!

On the left, 10:1 JPEG compression. On the Right 40:1 compression.
Uncompressed the image would look virtually identical to the 10:1 JPEG on the left.

With 10:1 compression the 8-bit files generated by a 3MP camera would be 900Kbytes in size rather than 9Mbytes, which is a big saving with little quality loss. The smaller files take up much less storage space and are much faster to send between computers or from the digital camera or memory card to a computer.

There are also lossless ways of saving files using TIFF (Tagged Image File Format) . These keep all the original information, but at the cost of much bigger files. TIFF files can be compressed in a non-lossy way, but they don't get very much smaller. For example, compare the file sizes for the rabbit image above: TIFF files can also be used to save 16-bit data (those these files are twice the size of 8-bit data files), JPEG files can only save 8-bit data.

Uncompressed TIFF	Compressed TIFF	JPEG at 10:1 compression	JPEG at 40:1 compression
176.1 Kbytes	157.6 Kbytes	17.4 Kbytes	4.5 Kbytes

Some cameras offer a third option, that of saving the actual data generated by the sensor in a proprietary format. Canon calls their version of this "RAW", Nikon call it "NEF". These files are compressed, but in a non-lossy manner. They are significantly smaller than equivalent TIFF files, but larger than JPEGs. Typically they achieve a compression of around 6:1 using 16-bit data, so files are 1/6 the size of equivalent TIFF files. The only disadvantage of these formats is that the image must be converted to either JPEG or TIFF for most software to be able to display them. The conversion is quite a complex process and can be time consuming if you have a lot of images to convert and a PC that's not very fast. Since the RAW and NEF formats contain more information than JPEGs (and in fact often more than TIFF files) you can do some degree of exposure compensation during conversion to JPEG to rescue otherwise improperly exposed images. You can also make white balance corrections during conversion, so if you shot with the wrong white balance, you can fix your error.

Display, Printing, DPI and PPI

There's lots of confusion here so I'll try to go slowly!

When you display a digital image on a monitor, the only thing that determines the size of the image is the pixel count and aspect ratio. DPI and PPI (and I'll explain them later) mean absolutely nothing. If your image is a 480Kbyte file which is 800 pixels wide by 600 pixels wide, it will display as a full screen image if you are using an 800x600 display. It doesn't matter if your DPI is set to 1 or 1000 or if your PPI is set to 1 or 1000. This is 100% true as far as web display goes and as far as any monitor display goes - unless some software intervenes. For example the IE6 browser will take large images and resize them so they fit on the screen. However DPI and PPI are still ignored. A few advanced page layout programs and advanced image editors may be capable of taking DPI and PPI into account when displaying images.

So I'll say this once again. The way you control how large an image appears on someone's monitor screen when viewing your images on the web is by changing the pixel count. If your original image is 1600x1200 pixels it will probably be too large to see all at once on 95% of the video monitors out there. It will also be slow to load since it will be a large file. If you want someone using an 800x600 display to be able to see your image clearly, you need to change the size to, say, 600x400 pixels (remember the browser window is smaller than the full monitor display). You change image size in software. All image editing programs can do this. Sometimes it's called "downsampling" or "downsizing". See your image processing software manual for details on what options your software offers.

PPI stands for "Pixels per inch" and is almost exclusively used for printing, not video display. If you take an image that is 800 pixels wide and 600 pixels high, and you print it with a PPI setting of 100 pixels per inch, the print will be 8 inches wide by 6 inches high. If you print at 200 PPI you get a print 4" wide by 3" high. Now the print at 200 PPI will be higher in quality but smaller. Most people seem to agree that around 320 PPI is the highest number you really need. Above that it's very hard to see any improvement in image quality. 240 PPI is often used and even that is often regarded as high quality. Most people notice a quality drop when they go below 180 PPI.

DPI stands for "dots per inch" and is a property of a printer, not a digital image. It's a measure of how finely spaced the droplets of ink can be in a print. However the number is a bit misleading since it's not always measured in the way you think it might be! Printer settings of 360dpi, 720dpi, 1440dpi and 2880dpi are often found. However the difference between then is subtle at best. Most people probably couldn't tell the difference and 360dpi usually looks great. Changing DPI does not change the size of the print. PPI controls that. DPI controls print quality (though as I said, over 360dpi you don't see much change).

Memory

There are quite a few different (and incompatible) memory cards used in digital cameras.

Compact Flash (CF) - The original memory card. 42mm x 36mm x 3mm. Somewhat larger than the others, but used on all high end DSLRs. Available in capacities up to 2GB. There are also miniature hard drives (Microdrives) with almost the same form factor as CF cards (CF type II, 5mm thick)) which are available in capacities from 340MB to 4GB. Microdrives used to be cheaper than solid state CF cards, though there is not a big difference today up to about 1GB. The 4GB Microdrives are actually cheaper than the 2GB CF cards though. Of course prices change pretty fast these days! Overall CF cards tend to be cheaper than any of the other forms of solid state memory - though this too could change. CF cards and microdrives contain their own disk controller, so that makes the camera electronics simpler.
Secure Digital (SD) - Very small - about 24mm x 32mm and 2mm thick. They have a built in write protect switch to prevent accidental erasure and certain encryption capabilities of little interest to digital camera owners.
Multimedia - Same size as SD but with less features and no encryption capability. There are some that can be used in some SD cameras but they aren't 100% compatible with SD cards in all applications.
Smart Media - Thinner than CF cards, but lacking an on-card memory controller. Despite the name, they're pretty dumb!
Memory Stick - Introduced by Sony and used only by Sony(?)
XD - Developed and used by Fuji, Olympus and Toshiba - even smaller than SD. 20mm x 25mm by 1.7mm thick

Is there any real difference in performance? No, not really. The CF cards are the cheapest per megabyte and are available in higher capacity models than the other (of course that may change with time). Most high end DSLRs use them. The smaller cards tend to be used in the smaller consumer digicams. There's really no reason to pick a camera with one type over another unless you have multiple cameras or other devices (MP3 players for example) which also use memory cards - then it's convenient if they can share cards. It may also be difficult (and/or expensive) to find really high capacity cards (1GB and up) in formats other than CF, but that's probably not a concern for most digicam users.

The following table gives the approximate number of shots you can expect to get using low JPEG compression using various pixel count cameras in conjunction with various sized memory cards at the lowest ISO speed settings of a typical camera. The exact numbers depend on how much compression the camera applies and the ISO speed used. Higher ISO settings result in more noise and noise is hard to compress and so leads to larger files and less images per card. If you're shooting in a RAW or NEF format you can divide these numbers by 3. If you're shooting TIFF files you'd have to divide these numbers by 8.

	3MP	4MP	5MP	6MP
128MB Memory	116	87	70	58
256MB Memory	232	174	140	116
512MB Memory	464	348	280	232

Approximate number of shots per memory card for various digital camera pixel counts using high quality JPEGs for storage

Digital Camera Interface

Once you've got the images stored in your camera on the memory card you need a way to get them into your computer! There are several ways to connect digital cameras to a PC as well as external card readers.

Serial - The earliest digital cameras had a serial interface, but no current cameras use this since it is so slow
USB 1.1 - USB was the first widespread high speed method of data transfer from cameras. It is theoretically capable of transfer speeds up to 11 megabits/second (note megabits not megabytes)
USB 2.0 - A development of USB but much faster - up to 480 megabits/second. USB devices are compatible with USB1.1 ports on a PC, but will only work with them at the lower data rate.
IEEE 1394 (Firewire) - Though this is an older interface than USB, it was originally only really used much on Apple computers. It's capable of high speed transfer (400 megabits/second) and it's now found on some PCs or it can be added to them via a plug-in card. More common on digital video cameras than still digital cameras.

Just about all cameras can connect to a PC, but it's sometimes easier to remove the memory card from the camera and insert it into a dedicated card reader. Even if your camera only has USB 1.1. if your computer has a USB 2.0 you can use a USB 2.0 card reader for faster transfer. Card readers are cheap, anywhere from $15 to $40.

Buying a Digital Camera

Sad to say there are more dishonest discount camera stores than you'll find in almost any other business. Some of the popular photography magazines are cram full of ads advertising very low prices. What they don't tell you is that you won't ever actually get the camera for that price. Either they will add on $75 in shipping charges or they will be "out of stock" on that model, but they will have a more expensive model available of course. Sometimes they'll tell you that the advertised camera is plastic in made in Taiwan, but for another $50 you can get the model made in Japan. Sometimes they'll ship you the wrong item in the hope that it will be too much trouble to send it back. Shop in the ads at the back of magazines based only on the lowest price you see and most of the time you'll be sorry.

However, there are reputable discount dealers and photo.net is associated with a few of them. These dealers do give photo.net a small commission on sales made through their website via the links below, so please use them if theu have what you want at a good price. They're honest, they stock what they advertise, they have low shipping charges, good prices and responsive customer service. If they didn't we wouldn't be associated with them and we wouldn't recommend shopping with them.

From http://photo.net/equipment/digital/basics/ 24/08/2011

Canon launches three new compact cameras

2011-08-23T23:53:00.000-07:00

The Canon IXUS 230 HS, Canon IXUS 1100 HS and Canon PowerShot SX150 released

Canon has announced the release of three new compacts in the 12MP, 8x optical zoom IXUS 230 HS, 12MP, 12x zoom IXUS 1100HS and the 12x zoom and 14MP PowerShot SX150 IS. The two IXUS models are impressively slim, with the usual sleek aesthetics that are indicative of the range, where as the SX150 IS is a compact superzoom.

The Canon IXUS 230 HS combines the slim, slender body and stylish aesthetics which have been indicative of the range since it's inception, with an impressive feature list including the HS sensor. As has been seen in the likes of the IXUS 220 the HS sensor allows for improved low light performance and a rapid burst rate. With an 8x optical zoom from a 28mm wide angle lens, 12.1MP sensor and 3" LCD screen there's plenty for the more discerning user to be content with as well as those after a fashionable compact. A high speed burst mode and slow motion movie is also included, and the IXUS 230 HS will retail at £229 and be on sale in October.

Where the Canon IXUS 1100 HS may contain a number of similar features to the IXUS 230 HS there are a number of noteworthy differences as well. The zoom is increased from 8x to 12x, still offering the same intelligent Image Stabilization. The LCD screen is a 3.2" LCD Touchscreen, which is impressive on such a compact camera, although the other specs are very similar to the IXUS 230 HS. Both cameras can also utilise a new external flash unit, the HF DC2, to add some more illumination when necessary. The IXUS 1100 HS will cost £369 and be available in October.

Finally the PowerShot SX150 IS is a compact superzoom in the same ilk as the SX130 IS, offering a 12x optical zoom and 14MP sensor alongside full manual controls. Although there is a lack of electronic viewfinder, as there was with the PowerShot SX150 IS' predecessor, this camera will be of interest to those stepping up from a more basic compact or looking for a DSLR backup. HD movies, a 3" LCD screen and a number of Creative Filters also appear in this £199 RRP model that'll be on sale in September.

From http://www.whatdigitalcamera.com/news/529824/canon-launches-three-new-compact-cameras.html 24/08/2011

Digital SLR Cameras Underwater

2011-08-23T23:46:00.000-07:00

Digital SLR Cameras Underwater
By Berkley White

Under Capt. Don's dock in Bonaire during the Digital Shootout. Nikon D100 with Sea & Sea DX-100 Housing and YS-90DX Strobes. Exposed for highlight detail. Nikkor 17-35mm set to 17mm, 1/250th, f6.3.

Film vs. Digital Overview

For background information on the advantages and disadvantages of shooting digital over film, please see our previous article . While digital might not be the solution for 100% of underwater shooters, my personal experience with underwater digital stills leads me to the following conclusion.

Digital is the best solution for all new shooters that are remotely comfortable with computers. The value of instant feedback is priceless. Experienced shooters that have a working knowledge and a high success ratio with film techniques will need to evaluate their options more closely. For myself, the new digital SLR's offer me the user interface and exposure control that I have been looking for and are only inhibited with their inability to capture extreme highlight detail at the same quality as film. Based on my experiences detailed below, digital, specifically the Nikon D100 is about to become my choice for 90% of my underwater work.

The 5.3 megapixel Nikon D1x and 6.1 megapixel Nikon D100 digital SLR cameras

Digital SLR's (DSLR's)

Single Lens Reflex (SLR) cameras offer the ability to view directly through the primary lens while shooting. This allows you to see exact composition and focus prior to squeezing the trigger. The new Digital SLR's (DSLR's) are creating quite a buzz due to their high-resolution sensors and affordable price tag. Prior to 2002, a digital SLR would run you somewhere between $6000 - $60,000. The new Nikon D100 DSLR is priced at a more affordable $1999 Underwater housing manufacturers will begin shipping D100 models in December 2002 and most should have full production by spring of 2003. Sea & Sea will be shipping a Canon D30/D60 housing in December 2002. Additional housings for Canon and Fuji DSLR cameras will also trickle in, however the majority of manufacturers will limit their production to Nikon models. Since the D100 will be best supported DSLR for underwater use, I am limiting the majority of the DSLR details to features relevant to this popular underwater model.

Feature	Compact Digital Cameras	Nikon D100
Size	small	large
Shutter delay1	¹ 2.0 ' 0.1 sec.	imperceptible
Resolution	4 ' 5 Megapixel	6 Megapixel
Media Types	various / limited	Compact Flash Type II
Battery Life	typically poor	good
Lens Selection ²	limited	large
Sensor Dust Problem	no	yes
Strobe Exposure ³	manual / auto	manual / TTL
Highlight Detail	poor	good
RAW file ⁴	no	yes
Macro Focus Accuracy⁵	poor	good
Viewfinder Size	none	small
Camera Cost	$200 - $1000	$1999
Housing Price	$250 - $1100	$1950 - $2900
Housing Options	large selection	limited selection
Please read further for an expanded discussion on these footnotes. ¹Once the shutter is depressed halfway and focus is captured, further depression of the shutter release will then record the image within 0.1 seconds. A full press will produce a 2.0 second delay (Olympus 4040). ²Although compact cameras have a limited lens selection, special underwater lenses are available that will produce greater wide-angle coverage than Nikon's widest lens (16mm) on the D100. ³TTL requires the use of a dedicated land flash in a housing. Most systems are shot using manual strobe technique, however, the Coolpix 5000 does offer an auto strobe feature that produces reasonable results. ⁴The Nikon Coolpix 5000 does offer limited RAW capabilities. ⁵When shooting with compact digital camera you compose and verify focus with the LCD screen. When using a DSLR you shoot through the optical viewfinder. When shooting macro (close-up) it is much easier to visually confirm critical focus through the viewfinder of a DSLR.

Digital stills can be captured with a variety of cameras including compact digitals and even video cameras. While these cameras allow you to compose images through the LCD screen, DSLR's require you to shoot through the viewfinder and use the LCD for image review only.

Compact Digital Cameras vs. DSLR's

I have shot film for many years, but gave digital imaging some well-deserved respect when housings became available for the three and five megapixel compact cameras. These cameras offered good resolution and file sizes capable of printing 8" x 10" photo-realistic prints. Certain images even printed well at larger sizes. Mostly driven by housing availability, I chose to use the Olympus 3040 and 4040 series cameras. I found the Olympus line to be very user friendly and their compact size was easy to travel with.

Faster focus and no shutter delay

While I thoroughly enjoyed shooting these compact cameras, I knew they would never replace my film system due to a few drawbacks. First, was the frequently aggravating shutter delay. Upon pressing the shutter release, the camera slowly went through the steps of focusing and then captured the image almost two seconds after depressing the button. While it is possible reduce this delay to 0.1 seconds by first pressing the shutter halfway to perform a pre-focus, the delay is a significant obstacle when trying to capture the moment.

The new DSLR's offer shutter delays that are only microseconds and are perceptibly instantaneous. The faster focus speeds of these cameras also quicken their response and tend to function well even in lower light. Unfortunately, the Nikon D100 doesn't have the powerful focus motor of the D1x or even the F100 since it is built around the N80 entry-level film SLR. I found the D100 to perform well except for the longer macro lenses such as the Nikkor 105mm Micro. I would recommend a manual focus ring when using this lens for extreme close-up work. To help the camera focus and minimize your frustration I recommend the use of a housing mounted focus light when shooting any type of close-up lens.

All digital cameras use removable media for image storage. The new DSLR's use CompactFlash Type II cards featuring the highest capacities on the market. The IBM Microdrive is a compact hard drive with tiny moving parts.

Media Types

Many types of removable digital media are on the market. The type of media in use varies from camera to camera and each type has a maximum storage capacity. Smart Media and Memory Stick cards are used by many of the compact cameras and are limited to a maximum of 128MB. Compact Flash cards are also used in compact cameras and all DSLR's. Compact Flash is a serious advantage as it allows capacities up to 3GB. These cards can store hundreds and even thousands of images depending on file type and resolution settings.

When shooting the Olympus 4000 in SHQ mode (highest JPEG quality) you can store approximately 50 images on the largest available card (Smart Media 128MB). When shooting the Nikon D100 in fine mode (highest JPEG quality) you can store over 300 images on a 1GB Compact Flash Card. These larger sized cards do come at a premium price, but offer great flexibility for multiple dives.

Bonaire reef squid at Capt. Don's house reef. Nikon D100 with Sea & Sea DX-100 Housing andYS-90DX Strobes. Nikkor 17-35mm set to 17mm, 1/160^th, f11.

Great White Shark off Guadeloupe Island. Nikon D100 with Sea & Sea DX-100 Housing. Nikkor 16mm, 1/125th, f8.

35mm Film Lens	16mm	17mm	20mm	24mm	35mm	60mm	105mm	200mm
D100 Crop	20mm	25mm	30mm	36mm	52mm	90mm	158mm	300mm

Lens Selection

As a general rule, most underwater housings for compact digital cameras use externally mounted wide-angle lenses. These lenses are actually quite good for their low price and offer 100 degree wide-angle coverage and macro down to 1:1 (life-size) reproduction. Since these cameras have built-in zoom lenses, they are quite flexible and can be used for a large variety of subjects. As if this wasn't flexible enough, most of these lenses can be added or removed while underwater and thus allow one to be ready for anything.

DSLR systems are designed for interchangeable lenses mounted directly to the camera body. These lenses are much higher quality than those found on compact cameras and also command a higher price. While most shooters will find that two or three lenses will meet their underwater needs, many will want to use their DSLR on land and will have a plethora of lenses to choose from.

The D100 is built around a CCD sensor that is smaller than the standard 35mm film format. For this reason, angles of view are cropped by a factor of 1.5x. This cropping effect has some advantages and disadvantages. If you're into small subjects, your macro lens will now effectively produce larger images. The 105mm Micro lens becomes a 160mm. While this is fantastic for skittish or tiny subjects, it requires you to back up a considerable distance to capture the full body of a reef fish. Maximum versatility is best with the 60mm Micro lens. It will allow you to more easily work with medium sized subjects, but still get tight for a good macro shot.

Unfortunately, cropping becomes a disadvantage when shooting wide angle. I use the Nikkor 16mm full frame fisheye lens to get the maximum coverage possible. It produces the equivalent of a 20mm lens on a film rig. Normally I prefer the full coverage of the 16mm, but this reduced coverage is perfectly adequate for most shooting. For medium sized critters, the Nikkor 17-35mm zoom works well at pulling tighter frames.

Three reef squid off Capt. Don's house reef. Nikon D100 with Sea & Sea DX-100 Housing andYS-90DX Strobes. Nikkor 17-35mm set to 26mm, 1/160th, f11

Bonaire sponge and sun. Note slight loss of detail and color shift in sunball. This image is also a good example of debris on the CCD sensor. This hair was on every shot. Nikon D100 with Sea & SeaDX-100 Housing and YS-90DX Strobes. Nikkor 16mm 1/250th, f22.

Great White Shark off Guadeloupe Island. I was surprised to see this much detail in this sunball. Far superior to the compact digital cameras. Nikon D100 with Sea & Sea DX-100 Nikkor 16mm, 1/125th, f5.6

Sensor Dust Problem

When removing interchangeable lenses on DSLR's you open the sensor area to the hazards of dust and moisture. Although the sensor is hidden behind a light-tight shutter, tiny bits of dust and lint can find themselves attracted to the statically charged sensor. Since a fresh section of film is not moving along the focal plane, these annoying little particles show up on every picture until you clean them off. Be very sure to follow the manufacturers cleaning instructions or have it done professionally. Compact digital cameras don't suffer these problems as the sensor is sealed behind a fixed lens.

Strobe Exposure - TTL vs. Auto vs. Manual

Digital cameras are unable to run the TTL automatic strobe technology used by most film cameras. Each digital camera manufacturer uses one of a variety of strobe exposure systems. Olympus compact digital cameras flash the built-in strobe twice using the first flash as a test and the second as a corrected final exposure. Most Nikon compact digital cameras use a light sensor on the camera body to judge proper exposure. While effective, both of these systems are not as accurate as the latest technology in use by advanced SLR film cameras.

The Nikon D100 uses a system called D-TTL. This system requires the use of a dedicated Nikon land flash such as the SB-80DX. A D100 owner wishing to use D-TTL is thus required to place a SB-80DX land strobe in an underwater housing. Strobe housings are available from Seacam and Aquatica. A preferred configuration is to use one of these housings as the primary strobe and a wireless TTL slave such as the Sea & Sea YS-90 as a second strobe.

Most users, like myself, have embraced the use of manual strobe technique. Since the camera displays the image immediately you can simply evaluate the image, make corrections, and shoot again. This is the primary reason I choose to shoot digital. Instant feedback is incredibly powerful. Just simply follow the digital shooters mantra, "Shoot, review, adjust, shoot." All you need to know is how to adjust your exposure. The easiest method is to simply adjust your strobe power. The Sea & Sea YS-90DX strobe provides a 12 power level adjustment dial on the back of the strobe. This dial is effectively a brightness ' darkness control. Most of our students just don't turn the dial enough. Just keep adjusting until you get the desired results.

Wide Angle Backgrounds

I knew the D100 would perform well for standard macro and close-up work, but I was most interested in its capability to record smooth-toned blue water gradients, light rays, and sun balls. I find the compact digital cameras limited in their ability to reproduce nice backgrounds when the sun peeps into the picture.

I was very impressed with the D100's ability to hold detail in the background. While it still will not reproduce the highlight detail of film, it is far superior to the compact cameras I have used. Blue water gradients are smooth and the shadow areas are full of detail. In fact, I feel that many of my test images produced more detail in the shadows than I would normally see on a similar film exposure. Even if a film exposure recorded this detail, it would be incredibly difficult to capture it on a scan. This makes shooting a digital original a real advantage since the majority of underwater wide-angle images include subtle details in the shadows.

When shooting directly into the sun, the highlight detail suffers. I found best sun detail was captured when shooting in deeper water and at high f-stops. Sun balls were certainly not reproduced with the same detail as film, but were far superior to my previous attempts with the compact cameras. Best results are still found by excluding the sun just outside the frame our framing in silhouette. Light rays are maintained in great detail when this exclusion technique is followed.

Raw Files

Most DSLR's have the ability to record images in the RAW format. This format offers maximum flexibility by allowing you to modify some image options at any time, even weeks after the shoot. When set to RAW mode the camera records the raw data from the CCD sensor and tags the file with your camera settings. In JPEG mode the camera would record the same raw data, but permanently apply your camera settings to the image and then compress the file to a smaller size. The beauty of the RAW file is that you can change your mind or correct for errors by applying the camera setting after the dive. Since RAW files are full size files, you maintain maximum quality by avoiding the potential image degradation incurred from JPEG file compression. RAW files are also in 12-bit color, which offers a greater color depth than regular 8-bit JPEG files.

Most people use the RAW format for the freedom of adjusting white balance settings post dive. You can think of white balance as an electronic filter that adjusts image color to best suit your shooting environment. For example, colors appear different when viewed under a light bulb or when outdoors under a bright sky. The camera's auto white balance system attempts to make your colors as accurate as possible, but the underwater environment is not something a camera engineer was thinking about when they designed the system. It usually performs well, but is not always perfect. Since the RAW format lets you modify these settings after the dive, you can tweak the control to maximize the richness of blue water or the punch of a bright red subject. Experienced film shooters will appreciate this control, as it is similar to changing from Provia to Velvia films.

Unfortunately, there are a few drawbacks to the RAW format. Since RAW images are not compressed by JPEG, they are sizable and slow things down. These files take longer to write to memory cards and occupy more space. D100 RAW files are 9MB and will quickly bog the camera down if you attempt to shoot more than three images in quick succession. These files also require special software to view and convert them into something a photo-editing program can work with. While this requirement is not a major obstacle, it does increase workflow time.

Bonaire reef squid. Nikon D100 with Sea & Sea DX-100 Housing and YS-90DX Strobes. Nikkor 17-35mm set to 35mm, 1/250th, f11.

Sea & Sea DX-100 Housing.

Simple versions of Nikon Capture and Nikon View software ships with the Nikon D100 for viewing and converting RAW image files. You can purchase upgrades for expanded capabilities or use third party software.

Macro Focus Accuracy

When shooting with compact digital camera you compose and verify focus with a LCD screen on the back of the camera. When using a DSLR you shoot through the optical viewfinder and the LCD screen is only used for image review. Shooting through the viewfinder forces you to keep the camera at your face and not at arms length. While it is nice to hold a camera out in front of you, built-in LCD screens are not capable of displaying critical focus when shooting close-up images of small subjects. It is much easier to visually confirm critical focus through the viewfinder of a DSLR. These optical viewfinders are much sharper and a necessity when shooting at the limits of a macro lens.

DSLR Viewfinder Size

The high end D1x features a bright full-size viewfinder. The less expensive DSLR's such as theNikon D100 are built on lower end camera bodies. As such they tend to have slower focus motors and smaller viewfinders. These small viewfinders are more difficult to view through an underwater housing especially when you have a mask full of snot. Housing manufacturers will hopefully recognize this problem and invest design time on more capable housing optics.

The Nikon D100 and Sea & Sea DX-100 Housing. The DX-100 began shipping in December of 2002. Other manufacturers are expected to release models by spring of 2003.

Housing Options and Availability

Just as most underwater video manufacturers limit their design efforts to Sony cameras, the majority of still housing systems are built around the Nikon line. Although Canon has increased in popularity with topside professionals, few underwater housings are offered for Canon systems. Certainly this will continue to change as new Canon shooters enter the underwater market, but it will be a slow evolution.

Conclusion

Digital is a reality and has now achieved marketable quality. Instant feedback is the Holy Grail for a shooter pressed for time in a unique environment. While DSLR's lack the capability to record highlight detail as well as film, they open the door to an entirely new set of underwater shooting rules. DSLR's record an incredible amount of shadow detail while avoiding the time consuming and costly art of scanning. The underwater environment is filled with low contrast shadow detail and these cameras record these details beautifully. If you are looking to go digital, DSLR's offer the best performance available, but come at a higher price and travel weight. They are faster, more accurate, higher resolution, and more versatile than any compact digital camera on the market.

DSLR camera bodies are analogous to computers. Every six months new models will overshadow the predecessors with higher pixel counts, faster processors, and larger formats. To make matters worse, housings for these cameras will almost always be a generation behind. As with computers, you just have to select the best model, take the plunge and not look back. Otherwise you'll find yourself always waiting for that next big feature rather than jumping in and getting your digital workflow established.

Selecting a System

If you are experiencing difficulty selecting the best system for your needs I highly recommend giving both a try. Backscatter offers trips and classes complete with demo gear and instruction. Please check our Trips and Classes section for schedules and pricing. As always you can give us a call seven days a week.

From http://www.backscatter.com/learn/article/article.php?ID=28 24/08/2011

Getting Smart on “Free” Android Phone Offers

2011-08-23T23:36:00.000-07:00

Getting Smart on “Free” Android Phone Offers
The Android is the operating software that Google has specifically designed and introduced to match that of Apple’s. It has been said that this kind of OS is designed to be able to bring out the best in mobile communication technology. Just like everything else, that is new and promises a load of benefits and features, people from all over the world would like to get their hands on one.

It is fairly common for people these days to try to look for a Free android offer. Not everyone can afford it and not everyone is a hundred percent sure of this particular choice. It is not unusual for some individuals to try something new – especially if it was only recently launched. To be honest, there are a few ways to be able to get one for yourself. However, proper precautions must be made as not all of these offers deliver what they have promised.

There are numerous websites that mention a Free android offer. You do not need to be excited, eager or skeptical to check the website. Curiosity is all that is required. There may be some that would sound and look too good to be true; at times, they are. Before you go checking out all the sites that you can find, there are a few important factors that you would need to remember to keep you safe and protected from being taken advantage of. First of all, no matter how promising the words on the website is, if they ask for money such as for a membership fee or to purchase a particular product that you do not really know of, stop. Do not fall prey to these kinds of offers. It may sound like it is a cheap thing that you can afford – even that of a single dollar. Think of it this way, if a hundred people said yes to paying a dollar to them, that’s a hundred bucks right there. Plus, there is no guarantee that you will be given the promised phone. If it asks you to buy something that, you do not know what for or have no use for, stop. You will only end up with a useless item in front of you and still, there is the risk that no phone will be given in return.

If you are really interested to get a free android phone, you can check on other websites and be safe with your choices. It is important that you think about your personal benefit before you say yes to anything. Whatever you decide to do, you will still lose something. For your personal welfare, it is best if all you will be risking is some time. You can be able to achieve this goal by joining the sites that promises to give you this new phone if you will be kind and generous enough to answer some of their surveys. You may be required to give a few general pieces of information – so no harm there. There are also others that will ask you to help them generate traffic volume in to their websites by providing some referrals. If that is all that they ask, then it is absolutely fine. In case they do not deliver their promise, you will not need to mope about it.

Author Resource:- For more information on free android phone, visithttp://www.freedroidphone.net/

Article From Base Articles

Is This The Best Camera Phone 2011?

2011-08-23T23:22:00.000-07:00

Because of 'happy slapping' we often see camera phones in the news for all the wrong reasons. However, this month three smartphones have made headlines for all the right reasons. Three Nokia N8 phones were used on a beach in South Wales to make the world's largest stop-motion film. So just how good is the N8's camera? Does it win best camera phone 2011? Or are there other camera phones out there that can compete?

It has to be said that the Nokia N8's specifications are impressive. The 12 megapixel camera uses Carl Zeiss optics, has automatic red-eye removal, autofocus, a whole bunch of manual controls for when you're feeling adventurous, as well as face recognition software. Very impressive. The video function is good too. Not only do you get the 12MP, but it is HD quality and there's a secondary camera for video calls.

Excellent stuff. But what other camera phones are available at the moment? And do any of them match up to the Nokia N8?

Well there are certainly other 12MP camera phones about, and we think that this selection will leave you spoilt for choice. The Samsung Pixon 12 was the first 12 megapixel smartphone camera we saw on the market, and thus a leader of the market for quite some time. An OLED screen with a 480 x 800 pixel resolution, support for DivX/Xvid video playback, it's certainly still a Nokia contender despite being a little older than the N8. Reviews are certainly favourable and the phone itself has all the smartphone features we expect from a high end phone.

The Sony Ericsson Sattio also boasts a 12 megapixel camera. A fun feature of this phone is that it allows you to take 9 pictures in just one second. You can then pick your favourite and delete the rest. Handy for those of us who are a little bit picky when it comes to your photographs! It has smile detection, touch focus, video light, and image stabiliser for those shaky moments. It's certainly a nice looking phone as well, with a wide screen and slim case.

So there you have it. Although the Nokia N8 may be making headlines, that doesn't mean that it wins the best camera phone 2011 award. There are plenty of other options. If you don't need 12MP then there are a number of 8MP camera phones available at the moment, with more coming out all the time. Nokia, BlackBerry, HTC all offer 8MP cameras on their phones, to name but a few. 8MP won't set you back a small fortune either, so look around for a good deal. There are also rumours that the new iPhone will feature an 8MP camera, so Apple fans should keep an eye out for that!

Author Resource:- About Mobile Choices: Mobile phones under £100 can still have great cameras, so if you're looking for one then head to Mobile Choices. You'll find smartphones, mobile phone coverage advice, and more on the informative site.

Article From Base Articles 24/08/2011

Canon PowerShot SX150 IS

2011-08-23T07:25:00.000-07:00

Canon has unveiled some new digital cameras. The new cameras are all in the compact range and promise to set new standards for capturing images. The new models include the PowerShot SX150 IS, the Elph 510 HS, and the Elph 310 HS. The first of the new trio is the SX150 IS with 12x optical zoom and a 28mm wide-angle lens. The 510 HS also sports 12x optical zoom. Canon claims it is the thinnest camera with 12x optical zoom to date.

The 310 HS has 8x optical zoom. All of the cameras have the 28mm wide-angle lens. The cameras also has a range of automatic features to choose the best settings for image quality no matter the environment. The three cameras use the HS System to reduce noise at high ISO speeds and expand the cameras dynamic range.

The SX150 has a 3-inch rear LCD and a 14.1MP resolution. It will ship next month for $249.99. The 510 HS and 310 HS are both 12.1MP resolution cameras. The 510 HS has a 3.2-inch touchscreen on the rear, high speed burst mode, 1080p video recording, and more for $349.99 with shipping in October. The 310 HS has a 3-inch LCD and will ship in October fort $259.99.

From http://www.slashgear.com/canon-powershot-sx150-is-and-new-elph-digital-cameras-break-cover-23173629/ 23/08/2011