Understanding Photography

DSLR Simulator

2011-06-07T01:34:00.000-07:00

Just a short entry, I just found this really cool DSLR simulator that lets you try every camera setting and watch the results. Why not give it a try and experiment a bit

http://camerasim.com/camera-simulator.html

Via: Twitter

Active Noise Cancelling Technology and the Nokia BH-905i [Off-Topic]

2011-05-28T13:11:00.000-07:00

It's been some time since I last updated the blog, since I rarely have time to. I wanted to write an article on active noise cancellation.

Last week Nokia sent me a BH-905i headset as a trial, thanks to WOMWorld and it got me thinking about Active Noice Cancellation (ANC from now on), so I thought I would share some insight on how ANC works and where you could find it more useful.

First of all which is the difference between active and passive noise cancellation?

Passive cancellation consists of isolating the ear or the sound source with any soundproofing material. You can find it in houses, cars, and even some computer cases. It works best with higher frequencies, i.e. higher pitch, is relatively cheap and consumes no energy.

However, passive cancellation doesn't work good with lower frequencies and often results in bulky devices, like isolating construction headsets.

Active cancellation was invented in 1934 and has been getting better ever since, but how does it work, and what is it good for?

ANC relies on the nature of sound. Sound is formed by waves, just like the ones in a water surface. If you have studied waves you probably have heard about destructive interference. Destructive interference is an effect which occurs when two opposite waves meet. Don't get me wrong, opposite doesn't mean that they are travelling in opposite directions, it means that one of them is on the crest and the other one on the trough, as shown in the picture by thescienclassroom

Both waves in the picture produce a sound by themselves, but add them in that exact point and they will cancel themselves out. This is basically what the BH-905i does.

Now, there are various ways to implement this and I don't know how it is done in this particular headset. You can take the simple analog approach, capture the sound, invert it and send it to a speaker, but it's not easy to generate the same wave (sound isn't going to be a pure sine wave like the picture above). Also you have the problem of doing it as fast as the sound propagation itself. Remember that the same wave, added in a different moment will not cancel the noise, but produce noise by itself. The microphones in a headset are like 1cm from the speaker which means you have to capture the sound, invert it and reproduce it in less than 30 microseconds, doable, but not easy.

Then there is the digital approach, which I think is the solution chosen for the BH-905i (I'm not an engineer at Nokia so I can't confirm this, I'd love to hear some insight from Nokia) this consists of digitally capturing the sound, decomposing it in different frequencies (through FFT) and then generating these same frequencies with opposite phase (which is the same as inverting the signal). Doing this allows the system to work with some delay and doesn't force the speakers to produce a very perfect sound. The result is that you get a really good attenuation for constant, low frequency noises. (Higher frequency noises mean shorter wavelengths, which means that crests and troughs are shorter and thus more difficult to put together) If you sit on an airplane for example, the engine is always generating the same soundwaves, since they're produced by components moving cyclically in the exact same way. This allows the digital system to capture the sound, analyze it and cancel it in a very efficient way.

The digital approach has a drawback, though. Processing the incoming noise takes time, so you can't cancel out random unpredictable noises like a conversation, steps or the wheels of a train against an uneven rail.

Summing up then, this headset, and others with similar working, is much more efficient at cancelling the noise of an annoying computer fan for example, than at cancelling conversations or similar noises.

I want to thank Nokia and WOMWorld for giving me the opportunity of trying this headset myself.

Creating Zoom effect on Photoshop

2008-10-17T12:17:00.001-07:00

In my last article I gave you an introduction to the zoom effect on digital photography and showed you how to shoot it with your camera. This effect however is very difficult to master and can be recreated in photoshop with practically identical, or even better results. This is what we're going to learn today.

First of all choose a suitable picture. It can be anything with a subject you want to make stand out. I chose this picture of my bike standing aside a bike trail.

Now you only have to go to filters->blur->radial blur. Here you select the amount of blur, you have to select zoom and you have to select the center of the blur effect (this is the point you want to be in focus). Also I recommend setting the quality to optimal.

Now take a look at the image, if you're satisified with the result then that's it, if not you can try changing the amount and the center of the blur until you like the result.

Also there is a way of making your whole subject stay in focus. If you only follow the steps detailed above, you'll end up with only a small focused point. If you're subject is large however, it will probably be out of focus. But don't worry there is a very easy way to fix that. Select your subject and copy it to another layer, now apply the effect on the background layer and your subject will remain in perfect focus. To select the subject I recommend using quick mask mode (pressing Q) and then painting it all. Once you're done get out of quick mask mode (Q again) and invert the selecion. Now you only have to copy that selection to another layer and you'll have your subject isolated from the background.

Now when you apply the effect on the background, your subject won't be blurred since it's in a separated layer. This is what it will look like:

And that's how you fake zoom effect on photoshop! I hope you found this tutorial useful, also I let you another example here:

Zooming technique

2008-10-02T13:28:00.000-07:00

And on we go with the slow shutter speed effects series! We learned how to do panning, how to fake it on the pc, and now we're going to learn how to use the zooming technique.

This is a very simple technique but can achieve some neat results when applied correctly. It consists of zooming your lens in or out while the shutter is open. This creates a kind of tunnel effect towards the center achieving a sense of speed.

Similarily to panning this technique requires the shutter speed to be the correct one. Slow enough to create the zooming blur, but fast enough to allow for a sharp image in the center. As always this speed will depend on your hands stability, focal length and whether you have image stabilisation enabled. I recommend you to use something between 1/10 and 1/60, take into consideration, that the faster you set the shutter speed, the faster you have to zoom in or out to make the image appear blurred in the corners.
If you have the time you can set a tripod and a slower shutter speed, say 1/2 por example and zoom in slowly, which will give you more stability.

Once you have set the correct shutter speed (Use shutter speed priority mode ) set your subject, or whatever part of the scene you want to be sharp, in the center of the image. Now click the shutter and zoom your lens in or out while it's open. This will blur the edges of the image, creating the zoom effect.

Also, you can combine the zooming in with panning to change the part of the image that remains sharp. For example, if you zoom in while pan the camera to the right, the sharp area will be on the right side of the image. Combining both effects however can be too difficult to the point that it becomes frustrating, so I would recommend you to reproduce the effect later on on photoshop if you want the sharp area not to be in the center. In my next post I'll show you how to do that easily, so stay tuned!

Faking panning on the pc

2008-09-30T10:24:00.000-07:00

In the last post I showed you how you could use the panning technique to give your subject a sense of speed and make it stand out from the background. I hope I have given you enough time to experiment a bit with the effect before showing you the easy way: creating it in photoshop.

Let's take a look at how it works.

We'll take a picture where both the subject and the background are sharp, I've chosen this one:

With the scene so bright and the helicopter moving so, relatively, slow it was impossible to use a shutter speed slow enough to create motion blur. So I decided to recreate it on Photoshop.

Firs thing you want to do is select your subject. I recommend going to quick mask mode (pressing Q) and then "painting" your subject with the brush.

Once you're done click Q to get out of quick mask mode and invert the selection. It's a good idea to copy the helicopter to a new layer.
Now all you have to do is select the background layer and go to filters->blur->motion blur

Here you can select the direction and the amount of blur. The direction will have to be the same as the on of your subject and you can vary the amount if you want to make it more or less blurry , I used 30 pixels, but it will depend on your photo so try different values until you're satisfied.

And that's it now you can recreate the motion blur in your photos without having to use panning. My advice however is to try and make the panning effect straight out of the camera, it will look more realistic and most important it will be much more fun!

Panning

2008-09-23T08:08:00.000-07:00

Some days ago we talked about how we could make our subject stand out using selective coloring. Today we're going to learn a technique that will make it stand out and give it a sense of speed. This technique is called Panning.

As you probably know when we shoot a moving subject with a slow shutter speed the subject will appear blurred on the picture. This is something you usually want to avoid, since you want your subject to be in sharp focus. The panning technique however, allows us to benefit from this effect by making the moving subject sharp and the background blurred. How does this technique work? This technique is very simple although it might require some practice. What you need to do is follow your subject with the camera, as long as the sutter is open. This will cause the subject to stay in the same position of the shot throughout the exposure, thus remaining sharp and will cause the background to have motion blur.

Only following the subject with your camera however won't cause the background to be blurred. First you have to make sure that there will be motion blur in your shot. To do that you have to set a slow shutter speed, I recommend using shutter speed priority mode. Setting the correct shutter speed is not easy, set it too low and you'll end up with an overall blurred shot because you won't be able to follow the subject precisely enough.

1/2--------------------------- 1/2

Set it too high and the whole image will be sharp, spoiling the speed effect.

1/495

I recommend using something from 1/6 to 1/60, but it will always depend on your subject's speed, proximity and your focal length.

1/60--------------------------------- 1/25

But setting the right shutter speed is not everything. You have to be able to follow the subject precisely, how do you do that? There is no perfect technique for that, you can use a tripod if the movement is completely horizontal, but I rarely have a tripod by me so I always do it handheld. What I recomemnd you is to start following the subject with your camera moving your whole upper body so that the movement is stable, when you feel you're moving at the same speed of your subject, click the shutter and keep moving with it until the shutter closes again, then stop moving. The most important thing of course is to keep the same speed as your subject while the shutter is open.

You can always use your flash together with the slow shutter speed to ensure you freeze your subject perfectly, but remember not to freeze the whole scene or the sense of movement will be spoiled. Also if you want to have more probablities of success use the burst mode of your camera and keep shooting as long as you can follow the subject.

And that's all I can teach you about panning, if you want to learn more go outside and practice, practice a lot, that's the only way to get this technique right!

PS: I'll write an article soon about how to fake this effect in photoshop, but don't rely on it, keep practicing, it's nicer and much more fun!

Photos by me and ttstam

Understanding Histograms

2008-09-18T12:07:00.000-07:00

If you've been using digital cameras for some time now, chances are you have already seen lots of histograms. They are shown by most cameras and imaging software and they are a very powerful tool to review your exposure. Today we are going to take a look at them and we're going to answer the question:

How do I interpret a Histogram?

A histogram is a graphical representation of a series of data, it's not only used in digital photography but also in many statistics representations. Every column in a histogram represents a case and its height represents how often this case is presented. Translated into digital photography, every column represents a tonal value, while its height represents how often this value is present in our picture.

The light values in a histogram go from 0, at the left meaning completely dark to 255, at the right meaning completely white.

This means, if a picture is dark the columns in the left will be higher, because a bigger part of the image will be contained in them.

It might sound complicated but let me show you some examples to make it easy.

This is the histogram of a normally exposed image. The tones are well distributed along the histogram from the darker to the lighter areas, there is a very high peak at the brightest end of the histogram showing the overexposed area caused by the light at the lower right corner of the image. These peaks are something to avoid, since parts of the image with so bright tones will end up just white without any appreciable detail. In this image though this is tolerable since the burned area is quite small. Also, we can see a wider peak in the bright area of the histogram caused, that shows the bright area on the wall that's being lit by the light.

What this histogram is telling us about the image is that it has a burned area, it has well distributed tones and an important area of the scene is brighter than normal.

Let's take a look at a completely different Histogram.

This image is was intentionally underexposed to give it a different mood, which is clearly visible in the histogram. If you look at its darker end, you will see how it contains a big part of the image. The brighter end is very low, filled only by some of the light rays and the clouds on the sky. Another important detail we can recognise in this histogram is that there are parts of the image in the very dark end of the histogram, as opposite to the image before, this shows that a part of the image will be shown black without any appreciable detail, once again this is something acceptable in this photograph because it creates the silhouette at the bottom of the picture. However you should try to avoid having values at the lower end of the histogram if you don't want any part of the image to be completely black.

So summing up, we have seen that a Histogram allows us to see how bright or how dark our image is, without having to rely on its brightness on the LCD screen, which can be affected by other factors like ambient light. It will also show us if we have burned or dodged any part of the image, so that we can notice if we have lost details in our picture, which is very difficult to see on the LCD screen only.

I hope this was a clear article, if you have any doubts or suggestions, don't forget you can let me know in a comment. Thanks!

Post-Processing: Sharpening

2008-09-16T11:26:00.000-07:00

In this article, I wanna show you an easy but essential post-processing technique: Sharpening.

Why do images need to be sharpened? Because of the digital sensor's nature areas with high contrast, like edges, are not recorded properly. This is because every pixel records only the average light that hit it and not the exact pattern. When a pixel in the sensor records an edge it won't record half a pixel black and the other white but will only record a grey pixel. I know this is a very simple explanation but getting into this topic would take a lot of time and all we want to do today is learn how to sharpen images, so how is it done?

Sharpening is something most comeras do automatically after taking a shot. In point and shoots the sharpening is usually enough, allowing the user not to post-process the image at all.
DSLRs though are designed for advanced photographers who want more control over their results. This is why they're configured to do a much softer sharpening in Jpeg and no sharpening at all in RAW files.

This configuration gives the end user the widest range of possibilities, because a sharpened image can not be desharpened, while an unsharpened raw file can be sharpened at will afterwards. Now we're going to take a look at how it's done.

If we're processing a RAW file in Lightroom or Photoshop the process is slightly different but the adjustments required will be the same. In this example I'm going to use photoshop.

Once you're done editing your image (sharpening should be performed the last), go to filters->sharpen->unsharp mask and you'll find something like this:

The first setting is amount. This determines the amount of contrast this filter will add in the borders. The higher the setting the more aggresive the sharpening will be, be careful though because it will come to a point where the image start to look odd.

The second setting is radius. This determines how many pixels around the borders will get the extra contrast treatment, same as before, the higher the setting, the more aggresive the sharpening.

The third setting is threshold. This lets you preserve smoother areas of being sharpened as well as the sharpening of noise. However this setting will affect the general sharpening negatively so i would preserve the smoother areas and the noise more selectively, by copying it to another layer for example. My advice is keep this setting low

As to the other 2 values there is no setting I can recommend you that will work on every image. You'll have to find out yourself which is the best for your shot. To do that start by raising the amount to around 400%. Then tweak the radius until the image is sharpened without visible artifacts, like halos around the sharpened objects. Keep in mind that the higher the resolution of the image, the higher the radius value has to be. Once you find the adecuate radius, lower the amount to a more reasonable value.
You can view the results in the small preview window or on the normal photoshop window. Keep in mind though, that to view the sharpening effect properly the image should be displayed at 100% or 50% zoom to avoid issues with aliasing of the images.

I set amount at 94% and radius at 1.8 and threshold at 4

I selected such a small radius for 2 reasons. First this image was at 6Mp which is not a very high resolution. Secondly there were small subjects with high contrast against the snow like the brown bushes, that would give a strange look if the sharpening radius was bigger than the details themselves, this something you will just realize when you try sharpening an image yourself.

These are my results

Before

Full image:
Before: After:

100% crop

Before: After:

As you can see the sharpened images have clearer details, which gives them a more realistic and "professional" look, while the unsharpened ones have a hazy effect, making them look unrealistic.

Tip: If you've read through this tutorial and found sharpening is way too complicated, you can always set you DSLR to sharpen the images automatically, which is done differently depending on the camera. Doing this, however, will give you much less control over the sharpening and can result in badly sharpened areas. What I recommend, as always, is shooting in Raw and then applying Lightroom's default sharpening settings, if lightroom gets it wrong you can effortlessly change the settings and the photo won't be ruined as would happen with in-camera sharpening.

Summing up I would say that sharpening is an essential post-processing effect, that should be performed on every image. I recommend applying a default sharpening filter in lightroom for your regular workflow and tweaking it when there is a special shot you want to sharpen perfectly or the lightroom's adjustments don't work well.

Post-processing: Selective color

2008-09-13T14:31:00.000-07:00

Now that we know how to convert photos to black and white I'm going to show you how to use selective color in your pictures.

Selective color is a very aggresive way to make your subject stand out by converting the rest of the image to black and white.

We're going to learn how to use it in photoshop.

This is the image we'll apply the effect to:

The stones have a very similar color to the background sand and rocks, making them stand out less than I'd like. To solve this we're going to convert all the background to black and white.

First of all we have to select the background, there are many ways to do this but I recommend using quick mask mode (by pressing Q), then going to brush tool and "painting" the stones, like this:

Press Q again to get out of quick mask mode and you'll have the background selected. What I like about this tool, is that using brush makes the edges of your selection soft, allowing some imperfection in your borders. Now you can go to the Channel mixer, like we learned in our previous article and do the black and white conversion.

Remember that the addition of all 3 levers has to be 100% if you want to keep the original luminosity of the image.

And there you've got your selective color effect! Now you can play with contrast, brightness and other options until you've got the image you want. Here's my end result.

Now the stones really stand out against the background, making the image much more interesting

This is another example of selective color

Is there any technique you'd specially like to use? Feel free to post a comment about it!

Post-processing: Converting to black and white

2008-09-13T05:25:00.000-07:00

When I created this blog, I wanted to write articles about photgraphy alone, but several users have expressed their interest in digital post-processing too, so I'm going to start a series of articles about basic post-processing techniques and programs.

Probably the most known post-processing effect in digital photography is converting to black and white. This may seem like it's an easy process but doing it well may require some practice.

What is Black and White good for? Sometimes the colors in an image don't express anything or don't serve to create the effect we want, in those cases converting into black and white can be the perfect post-processing effect, freeing our image of all those distracting colors.

First I will explain how to do this effect if you're using lightroom, which I recommend and will talk about in future posts.

We'll take this image as an example.

Open it in developing mode in Lightroom and click on grayscale and you get this result.

Now, you might be happy with this result but it's also possible that this is not the mood you were looking for in the image.
To me, for example the sky and the grass looked too bright. To change this you can go to the channel mixer and change the luminosity of those specific tones. This will make everything with that specific tone to appear darker or brighter in the final image. I changed blue, green and yellow and this is how it looked like in the end.

Lastly, you may want to change some of the general settings, I modified exposure and contrast, it's always recommendable to have the contrast lever higher than the brightness one.

This is the end image:

If you want to reproduce the results in other Image editors like Photoshop or the GIMP you have to look for the channel mixer feature (Image -> Adjustments -> Channel mixer, in Photoshop), then select grayscale and make the adjustments you like like I did in this tutorial.

In the next tutorial I'll teach you how to use selective color to make the subject stand out. Stay tuned and keep experimenting!

Video on DSLRs?

2008-09-12T10:42:00.000-07:00

I think I'll take a break from the tutorials and write an article about a topic, that is on every photographers head lately. Some weeks ago Nikon presented its D90, successor of the D80 with HD video capabilities, rumors say Canon will present a similar feature in one of its future cameras too and many users are asking themselves:

Should video be implemented on DSLRs?

This is a very complicated topic and I think many of us have formed an opinon without really thinking twice about it, so I'm going to try and write down all the positive and negative aspects of this new feature.

The first many people, including myself, thought when they heard about this new feature was, what for? DSLRs are specialized in taking pictures and don't need the video capabilities.
This answer however isn't really based on any facts or arguments but rather in our feeling about digital photography. But are there arguments against implementation of video on DSLRs? Let's analyze what negative points video might bring to DSLRs:

Size, the size of a video processing chip is ridiculously small.
Battery consumption, probably close to none when feature is idle.
Cost. Here's the only argument I think would be worth taking into consideration:

The cost of the video processing and encoding chip isn't probably too high. Maybe this chip will be embedded in the next generation of EXPEED processors in the future so it will sink even further. The development of the hardware and software necessary for recording video though can get more pricey. Considering Nikon has got no experience with video, putting its developers to work on that feature costs the company time and money, that they could be invesing in other features. This is something we can't deny, but we have to think: Is video really such an uninteresting feature?

Most of us probably have multiple devices able to capture video: Videocameras, Point and Shoots, mobile phones... but all of them lack a lot of things that video-enabled DSLRs will have:

Quality: Probably the most important difference between the devices mentioned before and the D90 is the quality. The resolution recorded by state of the art mobile phones and typical point and shoots never goes beyond 640x480 or 0.3 megapixels. The D90 however will record in 1280x720 pixels (around 1 MP) and the roumoured canon camera might go even further with fullHD, that's 1920x1080 pixels. A constant stream of 2 Mega-Pixels shots at 30 frames per second. Now, we are sick of saying megapixels don't matter on a digital camera. That is not true at this level. The difference in quality between a 6 megapixel and a 25 megapixel shot, won't be even noticeable in a computer monitor or a TV set, that is because a monitor or TV can display a maximum of 2 megapixels at the same time, and we're talking about very high resolution devices. The difference between 0.3 and 2 megaxpiels though is a very different thing. A good (FullHD) TV set will be able of displaying those 2 megapixels recorded by DSLRs, making the 0.3 megapixels of Point and shoots look ridicolous. Most videocameras also record at 0,3 resolution, except for the new HD video cameras. But the D90's sensor has some other advantages apart from the resolution, its ISO capabilities are much better than the ones of any of the devices mentioned above, allowing for shooting in very low light.

Versatility: What do Point and shoots, mobile phones and most videocameras have in common? They have 1 lens, may be prime lens may be zoom lens, but that's it. If you want any other lens or effect you've got no upgrade possibility. Changing lenses is something DSLRs are well known for and this capability will prove valuable in video shooting just as it does when we shoot pictures. It's not the same to record a sports event where we want to have a wide angle lens to record the whole scene as to record wildlife where we want to be able to stay as far away as possible using a telephoto.

Convenience: Have you never been outside shooting and wanted to shoot a video? Do you take an extra camera just to take short videos on your trips? With video on the DSLR you just need 1 device that will take pictures and videos, and both with outstanding quality, the D90 might have some issues like the lack of autofocus but those issues will be solved for sure in the future, a problem we can't forget so easily though is the size of the videos, that will only allow for shorter clips unlike with videocameras.
Creative Possibilities. A similar point to versatility, changing lenses allows for more creative videos and so does the small depth of field created by DSLR lenses that will allow you to make your subject stand out while other devices will just have all the scene in focus

In my opinion those advantages will in the future make video capable DSLRs well worth the extra price, and even more considering that price will get smaller with time. Also the user base of HDTVs capable of displaying HD video is growing bigger every day, which will accelerate the process even more. What do you think? Will future DSLRs all come with video or will this just be a forgotten feature? You can leave your opinion on the comments or vote on the poll.

Shooting silhouettes

2008-09-11T05:34:00.000-07:00

In our last post, I mentioned that we could create silhouettes in a very easy way, just by using the central spot metering mode . Now I'm gonna show you how to create this effect that can give such a distintive touch to a photograph.

What is a silhouette? A silhouette is created in the limit between an underexposed and a normally exposed area. This means that to create a silhouette we will need a source of light behind our subject that makes it darker than the rest of the scene, like in the example above.

But having that source of light won't create this effect by itself. If we use matrix metering mode (default mode) the camera will try to expose the whole image properly, spoiling the silhouette effect. What we want is the camera exposing properly for the lighter areas only, leaving the rest underexposed to create the silhouettes. To do that we will use central spot metering mode, you can read infomation in more depth in the last article, but basically you want to center the source of light in the frame and then use the AutoExposure-Lock button to tell the camera to expose properly for that lighter area. The darker zones will automatically be underexposed, creating the silhouette effect.

This technique is not very easy to use and will probably require some practice from you, but once you are used to finding light sources behind your subjects, you will be able to create very nice silhouettes.

TIP: As with many effects in digital photography, this one can we created in Photoshop too, so if you can't get to shoot silhouettes or you just don't get them perfectly, you can tweak them later on the pc. Here's how it's done in Photoshop

Open your image

Go to Image->Adjustments->Levels
Take the lever at the lower end of the brightness range and shift it to the brigther areas, like in this screenshot

Once the areas you want to silhouette are dark enough, click ok.
That's it, this is what it will look like now.

Note: This only works if the shot was taken with a light source behind and has already some silhouette effect. If the shot has none of that effect you'll need to select the area you want to silhouette (I recommend using quick mask mode, pressing Q) and then repeat the same procedure.

And that's it for now, I recommend you not to take the easy way and try to take the silhouettes straight in the camera, but if not you can always cheat your way to perfection :D . Experiment and have fun

Understanding Metering modes

2008-09-09T06:51:00.000-07:00

In our series of articles about "Mastering the basics" we learned about the different settings to use to get the right exposure, but we never talked about the way we metered available light.

Now, we're going to take a look at the camera's metering modes.

Every modern camera has a sensor that measures how much light is getting through the lens. In most cameras we can chose how we want the camera to do it. There are 3 different metering modes:

Matrix metering: The most used of all modes, the camera measures light from all points in the scene, and attemps to set the exposure in a way that the whole scene is properly lit.
This is a very easy to use and effective metering mode because the largest possible part of the image will be properly exposed. Similarily to the auto mode, though this metering mode has its limitations when we want to have some advanced control over the resulting image.

Center weighted spot metering: This mode comes in very handy when shooting differently lit scenes. Imagine for example, that you're shooting at a concert. The whole scene is dark, except for the performer in who is lit by spotlights. Using the matrix mode, the camera will try to expose the biggest part of the scene, as a result the preeminent darker zones will be properly exposed, while the performer will be overexposed. This will be in many cases far from the ideal result. In these situations we'll use the center weighted metering mode, now the camera will prioritize the area in the middle and expose properly for a portion of approximately 25% of the image around its center.

Photo by sint

Central spot metering: This is the most selective mode, the camera will expose properly for a point situated in the exact center of the image. The rest of the scene will not be taken into consideration. I do not recommend this mode in most of the cases because light can change a lot from one point to another and the readings won't be very useful if we use one point only. It can be a good mode to use if we want to select an exact point for the camera to expose properly though which can be useful for example for creating silhouettes or for complicated light situations.

Now, when you read about the last two metering modes you were probably asking yourself, what about the framing? What if I want the performer in the concert to be properly exposed, without framing him in the middle?

Well, camera designers were aware of this problem and that's what the Auto Exposure Lock button is for. Most DSLRs have this button that allows you to lock the exposure settings once your camera has taken the light readings and adjusted its settings accordingly. This will allow you to take the light readings from the performer by placing him in the center and then, with the AE-Lock button pushed frame the shot as you want to.

Summing up: Center weightered and center spot metering modes, allow you to chose the part of the image you want to be correctly exposed, while matrix metering mode will try to have the whole image exposed properly.

Shooting star trails

2008-09-05T18:19:00.000-07:00

In our last article we learned how to shoot all kinds of light trails, now we're going to take a deeper look at how to shoot star trails.

First of all. What are star trails?

When you look at the stars at night, they seem to be stuck, but if you stare for a couple of minutes you'll start to realize that they're moving, only very slowly. This effect is created by the earth's rotation and not by the movement of the stars themselves. Every star in the sky makes a whole turn around the pole star. This particular one is right in the axis of the earth's rotation and this causes it not to move in the sky and always head north, that is why this star has been used by travellers thousands of years ago to guide themselves in the night, yes I like science :D but we're moving away from our main topic.

What is the effect of this motion when we shoot stars at night?

If we shoot stars with a shutter speed long enought to capture this movement, the stars will create trails in the form of circles around the polar star, decorating our shot with a very interesting sky.

How do we set up our camera to achieve these results?

This will be a little more complicated than with standard light trails. First of all you will need a remote control, or any other device that allows you to use the bulb mode of your camera. Setting up the maximum 30 sec exposure configured in your camera won't be enough to capture the star's movement.
To set up bulb mode we'll need to go into manual. Se the ISO to minimum, aperture preferably to a high value and shutter speed to bulb mode. Set the focus to manual and focus on infinity.
I also recommend using a long focal length because stars will appear to move faster when the lens is zoomed in.

And this is it, you can start to experiment with different compositions and shutter speeds, keep in mind however that very long shutter speeds will create too much noise in the image, remember turning the noise reduction function of your camera to minimize this effect. If you want to have longer trails, you can create a series of relatively short exposures and then blend them together in photoshop.

It is important to be able to identify the pole star, since all the stars will turn around it, making it a strong subject of your composition. To find it look north and find a very bright star.

And last but not least, keep in mind that this kind of photography works best at clear skies without luminic contamination, so run away from big cities.

Photographs by Corica, Warner Strauss and me.

Shooting light trails

2008-09-05T09:03:00.000-07:00

If you've read the "Mastering the basics" section you already know a lot about how to use the exposure settings creatively. In this article we're going to take a look at using long shutter speeds to get light trail pictures.

What you're going to need:

A tripod. When shooting at speeds longer than a second the use of a tripod is a must, trying to take these images handheld will result in very blurry images. You can however try to lay the camera on some stable surface but this limits your creative possibilities a lot.

A DSLR or Bridge Camera. Most point and shoot cameras don't allow for exposures longer than 1 or 2 seconds so we'll need to use a DSLR or bridge camera that lets us choose the shutter speed.

How is a ligh trail created?

The creating of light trails is very simple. When we let the shutter open for a long time any bright light that goes through the camera's field of view, will create a trail of light through the image. Used properly these trails can create very nice effects on roads and can be an interesting addition to a cityscape shot.

The first thing you have to do for getting a light trail shot is finding a place with moving lights, a typical location to start at is a driveway. Set your shutter speed to a value between 5 and 30 seconds, I recommend using the Shutter speed priority mode . Now mount your tripod and frame the shot. Once a car approaches, click the shutter button. The lights of the car will create a light trail on the image as long as the shutter is open. Review your results and try using different shutter speeds.

Using flash. Although flash is not often used in light trail shots it can create a nice effect showing the object that creates the trail and the trail itself. I recommend using rear curtain flash, in this mode the flash is shot just before closing the shutter and it makes the subjects lit by the flash appear at the end of the trail. Something like this:

Going back to the techincal aspects, i recommend using a low ISO and enabling noise reduction in your camera's menu to reduce digital noise from the long exposure.

An interesting addition to our gear if we want to shoot light trails often is a remote control. Triggering your camera from a remote has 2 advantages:

1. We won't need to touch any button on the camera, eliminating every chance of creating blur in the image.
2. It will allow us to use bulb mode, in this mode you'll be able to open the shutter with one click of the remote and closing it with a second click. This way you can't exactly control how and where the trail is created.

A very special kind of light trail are star trails, but we'll talk about that in the next article so stay tuned!

Creating Panoramas

2008-09-05T03:39:00.000-07:00

When we see panorama pictures we tend to think that these are taken with very specialized equipment. While this might generally be true, there are very easy ways of creating our own high resolution panorama with only a point and shoot camera or even a camera phone.

In this post. We,re going to learn how to use Hugin, an open source program, to create our own panoramas.

First of all we have to take the pictures. You need to take several pictures, as many as you want, that overlap themsleves partially on the sides, like this:

The overlapped area doesn't need to be as big as in the example, it will be enough with overlapping 30% of the image.

This will help the software find similarities between the images in order to stitch them together properly.

Now we will install the program. Download the installer from here. Once the program is installed, launch it and load the images you want to use for your panorama. Click on the load images button. Once you have selected the images, the program will start to align them automatically, if not click on the align button. This process may take some time depending on your computer and the size of your images, once it's finished you'll be presented with an image like this:

You can adjust the margins here so that you've got no black background, but I recommend you fix this in photoshop or any other editing program later. When finished close this window.

Now you only have to click on Create panorama. Select the folder and filename and you're done. Hugin will automatically stitch the images together and blend the margins making it look as a single image. When the process finishes, as before this may take some time, you'll have you image saved in .tif format.

Open it in your favourite editing software, cut off the black areas and you'll get something like this:

As you see this tecnique requires no special equipment and is very easy to learn. You can use any shots you want even those from a camera phone if the quality is enough. This is what I got from a couple of shot taken with an N95.

If you want your image to be of even higher resolution you can take the shots vertically, which will allow you to use more shots to put together the same field of view. This example is made with 5 vertical shots put together.

So, as we've seen it's very easy to create your own panorama shots by just shooting consecutive images and then stitching them together on the pc. Next time you go shoting landscapes, give it a try!

Shooting in RAW

2008-09-04T16:13:00.000-07:00

When I was thinking about this post I was considering making it a RAW or Jpeg post, but after giving it some thought I think to me this question has a definite answer.

Shoot in RAW

Ok so why do I have such a firm opinion on the question?

Well, first of all let me introduce you to the topic.

RAW and Jpeg are 2 different image formats implemented on most modern DSLRs. We can configure our camera to store the images in RAW, Jpeg or both.
Now, what are the advantages and disadvantages of both filesystems? We'll start out analyzing how Jpeg works. When your camera captures an image configured in Jpeg it doesn't save what comes straight out of the sensor, instead it applies a series of automatically adjusted "filters" that adjust contrast, saturation, white balance etc. After that the camera compresses the image almost without losing quality and then saves it to the memory card.

The way the camera handles RAW files though is pretty different. When configured in RAW the camera will save the information coming out of the sensor without applying any further adjustments to the image.

Of course this lack of post processing and compressing has some issues. RAW files need specialized programs to be opened, like lightroom or picasa, but if you're a serious photographer you'll want to use one of those programs anyways so that isn't a problem. If you still consider this an issue you can always shoot in RAW+Jpeg so that you have a Jpeg copy of your RAW just in case you want to open it with other programs or in other devices other than a pc. Also shooting in RAW will occupy more space on the memory card, but with today's memory card storing 8gb at very reasonable prices I don't think this could be an issue.

Now back to the question at the beginning. Why do I encourage you to shoot in RAW?

The answer is simple: You're smarter than you're camera. (Ok most of you)

When you shoot in Jpeg your camera will automatically adjust a lot of settings according to its preferences, if you shoot in RAW instead your camera and developing program will only suggest the settings used but you will be able to adjust every one of these yourself. During this process you will be able to see how any of these changes affect the end result allowing you to adjust the processing to your very own taste.
This may sound like it's a feature only image enthusiasts would like to use but, trust me, it comes in very handy at shots where your camera's metering is fooled by special lighting conditions rendering it unable to create a decent image.

So all in all, shooting in RAW doesn't slow down your workflow in any way and it does give you a lot of options to adjust shots to your exact taste or to fix shots the camera didn't get too well.

Have a different opinion? We all can learn from each other, feel free to post a comment about it!

Camera modes

2008-09-04T12:16:00.000-07:00

Now that we know the effects that every setting has on our image, we're going to learn how to tweak those settings in our camera's menu. It is possible that your camera has a different menu system but usually all DSLRs have the options I'm going to talk about.

Auto: Not much to say about this mode. It is fast and useful for the times where you just haven't got the time to think about the settings. The camera makes all the decisions about the exposure and even the metering modes, but now that we've learned how to use every of those settings, we want to have control over them, right?

P mode: This one is similar to auto mode, you set the ISO and the camera will automatically set the shutter speed and aperture for the shot. Also P mode allows you to control the metering modes, something we will talk about in future articles

Shutter Speed priority: This is were we start to take control of the settings, this mode will allow us to set the shutter speed and ISO we want and the camera will adjust the aperture to match the available light. Very useful for taking action shots or for playing with motion like we saw in the article about Shutter speed.

Aperture priority: This mode allows us to control aperture, and ISO while the camera will take care of adjusting the shutter speed. This mode is very useful for taking control of the depth of field like we saw in the article about aperture.

Manual: This is the mode, where you control everything. ISO, shutter speed, aperture, metering modes, white balance... .This might sound like it's the ultimate mode to use once you understand every setting, but in my opinion this mode makes it too difficult to get a correctly exposed shot, since it will be you that will have to tweak every setting until you get the correct amount of light. There are moments though where this mode will be the only option, like when you want to use the bulb mode of your camera. This mode allows you to have the shutter open for as long as you want and can be helpful for making very long exposures, like in star trail shots.

So, you will be asking yourself, which mode should I use?

The answer to this question depends on your skills and the situation you're in, as i said before you can use auto mode if you want to take a photograph quick without losing time on adjusting the settings, but the rest of the modes will give you more control over the shot.
I personally find myself shooting usually with P mode that allows me to control the ISO so that the camera doesn't accidentally bump it too high ruining the shot because of the noise. When i want to use some of the exposure settings creatively I just go into aperture or shutter speed priority mode, since they're much easier to use and will give you identical results to the manual mode.
Sometimes you'll just need to use the manual because the camera won't be able to get the shot exposed like you want. Don't be afraid of using it now that you know what every setting does, do keep in mind though that it will probably take some time to get the shot properly exposed. But hey you're doing this just for fun right? Just take your time and enjoy experimenting!

Mastering the Basics: Understanding Aperture

2008-09-04T08:53:00.000-07:00

After having learned about shutter speed and ISO settings, now we're going to take a look at the aperture.

The aperture setting is the size of the opening in the lens.

Every lens has a couple of blades, called iris, that are put together to regulate the light that gets through, depending on the aperture setting used.

The aperture is indicated in the camera as the f number. A high f number will represent a small aperture while a small f number will represent a big one. This might sound counterintuitive but is easier to understand if we imagine the f number in the formula 1/f. The higher the f number the smaller the end result.

But enough with the technical details, what is aperture good for?

Tweaking the aperture settings will not only control the light intake, but will also control the size of the depth of field (In short, the depth of field is the part of the image that is in focus). This will allow us to use the depth of field that we find appropiate for our shot. Imagine for example that we are taking a portrait picture. We want everything in the background to be out of focus, so that it doesn't distract from the main subject. In order to achieve that we will use a small f number, that will result in a big aperture, creating a shallow depth of field.
If we were shooting a landscape for example we would do the exact opposite so that all the parts of the image stayed in focus.

The maximum aperture setting will depend from each lens and is an important factor to have in mind when buying new gear, prime lenses, those without zooming possibilities, are the ones which allow higher apertures. It is easy to find cheap prime lenses allowing for f1.8 apertures and more expensive ones even allow for f1.4 or f1.2. Zooming lenses instead have smaller apertures and their maximum aperture varies depending on the focal length used. The 18-55mm kit lens from the D40 for example will allow for a f3.5 aperture at 18mm but only f5.6 at 55mm. Zooming lenses with bigger apertures are only found in the professional level and are used by sport photographers for being able to capture fast shots even in low light.

Summing up, rising the aperture setting will let in more light while making the depth of field smaller and the maximum aperture depends on the type and the quality of the lens.

Mastering the Basics: Understanding ISO

2008-09-04T06:17:00.000-07:00

In the last article about the exposure triangle we took an in-depth look at the shutter speed and we mentioned how sometimes it was better to use a slow shutter speed than a high ISO. Now we're going to analyze why this happens.

First of all what is the ISO setting?

The ISO setting represents the sensors sensitivity to light.

Getting into more technical details, the ISO setting in digital photography is the gain of the sensor's signal. Although we speak about digital photography the camera's sensor itself is an analog device, just like a microphone for example, and as such its signal can be amplified to get more light into the picture.

This can be useful because it will allow us to use a faster shutter speed or smaller aperture when we need it (see article about shutter speed), but amplifying the signal will create noise, which will translate into small color dots in our image like in this example photograph. Depending on the camera and the ISO setting this noise can go from slightly visible to spoiling our image. Most modern DSLRs will be able to handle noise from ISO 200 to 800 at acceptable noise rates, but it's always a good idea to keep ISO at its minimum and only rise it when the we're forced to.
As an example a typical situation where you're forced to rise the ISO is at concert photography, where there is dim light and you can't use slow shutter speed because the subject would be blurred, in that case you can only rise the ISO, although you know you will have an image with some noticeable noise.

Summing up all you need to know about ISO is that you have to keep it as low as you can by using, when possible a slow shutter speed or a big aperture.

Mastering the Basics: Understanding shutter speed

2008-09-03T16:01:00.000-07:00

In my last article I mentioned how tweaking every setting to get the correct exposure had it's pros and cons. The first setting we're going to take a look at is Shutter speed.

The Shutter speed is the amount of time that the camera's sensor is exposed to light.

This simple setting has a great impact on the end result of the photograph. Using a fast shutter speed will freeze the moment, while a slow one will capture motion in the shot.
Keeping this in mind is very important because we will need to change this setting often depending on the type of photography we're doing. A classic example for this is sports photography. At sports events we're often photographying fast moving subjects, so we will need to set a fast shutter speed to capture the moment.
Sometimes though we will want the photograph to show the movement in the scene. Using a slow shutter speed moving objects will be blurred giving the viewer a sense of speed.

The problem with slow shutter speeds is that it's difficult to hold the camera completely still, so at certain speeds the whole photography will become blurred.

Sometimes we will need to use a slow shutter speed because there isn't enough light available even when rising the ISO and aperture. When this is the case it is very useful to use a tripod that will allow us to have the camera completely still during the exposure of the shot. Using a tripod will also allow us to use very long shutter speed to create interesting effects like light or star trails, which we will talk about in further articles.

Mastering the Basics: The Exposure Triangle

2008-09-03T05:14:00.000-07:00

Before we go into more advanced aspects we have to master the basic aspects of photography. The first concept to understand is the exposure triangle.

The exposure triangle is a representation of the 3 settings that will determine how much light reaches the camera sensor.

It consists of three elements.

ISO: The sensor's sensitivity to the light
Shutter Speed: The amount of time the sensor is exposed to light.
Aperture: The size of the opening in the lens that lets light in.

An easy way to understand this is to imagine a hosepipe: The aperture is the width of the pipe, the shutter speed is the time the pipe is open and the ISO setting is the pressure.

As you can imagine from the example above, there are several possible combinations that will let in the same amount of light, like for example increasing the shutter speed and then compensating that by decreasing the ISO setting, something common for night shots.

When we use the auto mode of our camera, it will automatically chose a combination to let the correct amount of light in, but while the amount of light will probably be correct, the combination used may not be the best one to get the results we expected from the shot. This happens because each of the combinations has its advantages and disadvantages that will depend on how and what we're shooting. If we want to be able to chose the combination of settings ourselves we will have to take a look in greater depth to each of the three settings: ISO, shutter speed and aperture, which we will do in the three upcoming articles.

Presentation

2008-09-03T04:41:00.000-07:00

This is my first post so first of all i'm going to present myself. I'm a 17 year old student from Barcelona with an interest in photography. Being a technical oriented person it is this aspect that I understand and manage the best. Through my relationship with other amateur photographers I've realized that lots of people who may be excellent in the artistic elements have a lot of trouble coping with the technical difficulties of taking good pictures. In this blog i'm going to try and share my knowledge in a way that it is as easy to understand as possible. So if you're afraid of moving out of the auto mode on your DSLR or just want to improve your technique this is your blog!