Seattle Sunset

2007-11-28T15:09:00.000-08:00

First Infrared Photographs

2007-11-28T14:48:00.000-08:00

HOW TO TAKE A CLEAR AND PROPERLY EXPOSED PHOTOGRAPH - An essay that I wrote

2006-10-04T22:39:00.000-07:00

This is an essay that I wrote last year. It may be a bit technical, but it also may help inform you about digital cameras and how to use them

HOW TO TAKE A CLEAR AND PROPERLY EXPOSED PHOTOGRAPH

This guide is based on settings for Digital Single Lens Reflex (DSLR) cameras, but many of these settings can also be applied to other more basic cameras. In order to adjust these settings and any camera, one will need to switch his or her camera to manual mode, which can usually be done by turning a ring on the top of most cameras to the “M.”

A DSLR camera is a digital camera with interchangeable lenses. What separates regular digital cameras from DSLR cameras is that when one looks through the viewfinder, one sees exactly what the picture will look like, instead of looking at an LCD screen which could be misleading. LCD screens are screens on the back of non-DSLR cameras that are a substitute for a viewfinder. LCD screens provide a digital display of what one would be seeing if one were looking through a viewfinder. Since it takes time for the camera to process what it is looking at and then put it on the LCD screen, what one is seeing on the screen is not in real time; it is delayed a bit (delay time varies depend on the camera, and many more factors).

There are many different factors and variables when taking a photograph with a DSLR camera. The main factor is exposure. Exposure has many sub-variables and factors that affect it such as shutter speed, aperture, and film speed.

Aperture is a unit that measures how wide the lens/shutter opens when taking a photograph. It can also be called f-stop. F/2.8 is wider than F/5.6; therefore, F/2.8 is going to let more light through the lens which will result in a more exposed (brighter) image than a photo taken with F/5.6. Taking a photograph with F/5.6 may not produce a photograph as exposed as F/2.8, but it does provide a larger depth of field. Depth of field (DOF) is the distance behind and in front of the subject in the photograph that is in focus. The smaller the F-stop is, the larger the DOF will be. A large DOF allows objects at many different distances to all be in focus at the same time. For choosing the right aperture, one needs to decide if one needs it wider for more exposure, or if one needs it smaller for a larger depth of field.

The other factor that makes up the exposure is shutter speed. Shutter speed is measures in seconds, usually in fractions of a second. Shutter speed is how fast the shutter opens and closes to take the photograph. A shutter is an object in between the lens and the camera's sensor that blocks out light until the image is ready to be taken. When the picture is taken, the shutter will open up for the amount of time that one has specified, and expose the sensor, to the light. The sensor will then capture the image and the shutter will close. The longer the shutter opens for, the more light reaches the sensor, resulting in a more exposed image. The faster the shutter speed is, the more stable (less blurry) the image is going to be, but one may need a slower shutter speed in order to get a properly exposed photograph. This is why photographers use tripods. The tripod holds the camera, insuring that the camera is stable, so that blurriness does not occur. On a nice day, when outside, shutter speed should not be a problem. This is because it is bright enough outside to send enough light into the camera's sensor, even with a small shutter speed. It is easily possible to take photographs outside with a shutter speed of 1/500 to ensure no blurriness, and still produce a properly exposed image. When inside, 1/500 will usually result in a almost complete black photograph. Sometimes 1/200 will do the job inside. Once one gets bellow 1/160 one might start be getting problems with blurriness. The trouble is that sometimes one needs to set a low shutter speed if the area is too dark. There are many things that can help this situation. There are special lenses for cameras called “Image Stabilized lenses” by Canon, and “Vibration Reduction lenses” by Nikon. These lenses add about three steps in shutter speed to what the shutter speed is already set to. If the shutter speed is set to 1/60, the lens would stabilize the image equivalent to using a shutter speed of about 1/130 (maybe more), but the exposure of the image would still be that of a photograph taken at 1/60. Using lenses such as these can really improve exposure. These lenses can also be very expensive. I use one of these for taking photographs of basketball, because it is inside, and I need a fast shutter speed to capture the action, but I also need the photograph to be properly exposed. Since these lenses are so expensive, there is another way of solving the problem of needing a fast shutter speed in an area with low light levels. This can be achieved by adjusting the film speed.

Although digital cameras do not take film, they still have something called film speed, which sets how sensitive the camera is to light. Film speed was formerly measured in ASA because it was based on the photograph exposure system developed by the American Standards Association. Film speed is now measured in ISO, based on the exposure system developed by the International Standardization Organization. Most digital cameras have an ISO range of 100-1600, but a few can go up to 3200, or as low as 80. Setting a high ISO can improve the exposure of an image. As always, there are consequences of setting higher ISO values. The lower the ISO is set, the less exposed an image will be. The higher the ISO is set, the more exposed an image will be, but with a consequence. Setting a high ISO can result in noisy images. “Noisy” is a term used by photographs that means grainy. An image with a lot of noise, will have little speckles and grains in the image. There are many computer programs that can help reduce noise in a digital image once it on a computer, and some of them are pretty effective, but none are completely effective. Certain cameras are able to produce clearer images at higher film speeds. Cameras such as the Olympus E-500 have noticeable noise in photographs even at an ISO of 400, but cameras such as the Nikon D50 can take photographs at an ISO of 800 with noise barely visible. Some cameras like the Canon 20D can even take photographs at 1600 with almost no noise, which also means that images taken at 100 or 200 ISO with a camera like this are going to be very clear and smooth looking. The amount of noise levels at each ISO setting really varies from camera to camera.

In order to take properly exposed photographs, one will need to take all of those factors and choose the best settings in each of them for the photograph. One can make adjustments on certain settings based on the settings of the other factors. For example, if one has a lens that is able to go as low as F/1.8, remember that when choosing a shutter speed. Since one can open the lens as wide as F/1.8, one could probably use a higher shutter speed than normal and still get a properly exposed image. If one is taking with a flash, one could easily set a very low ISO, a high shutter speed, and a small aperture, and still get a properly exposed image.

The last thing to know is how to actually take the photograph. Once one has gotten all of these settings right for the photograph, one needs to take the picture. Many people press the shutter-release button, and wonder why it took so long before the camera took the photograph. Sometimes people think that it had something to do with the shutter speed, but it doesn't. The camera needs to use it's auto-focus/electronic focus (AF/EF) system to focus on the subject (what one is taking a photograph of). The time that one has to wait, is the time that it takes the AF system to focus in on the subject. In order to have the camera take the photograph as soon as one presses the button, one needs to use the AF lock. This is done by pressing halfway on the shutter-release button. This applies to all digital cameras. Most cameras, such as the Canon EOS 350D (digital rebel XT) will make a small beep once the focus has been locked. Then one knows that it is safe to take the photograph. After one hears that beep, all one needs to do is finish pressing the shutter-release button, and the photograph will be taken instantly. All DSLR cameras and some regular digital cameras have special continuous modes that allow one to hold the shutter-release button down, and have the camera take multiple images in a row to ensure a good photograph.

There may be more factors of the type of photography that I am doing that could affect my decisions for these settings. I also experiment a lot with these settings to test what works in different situations.

There are many more important facts in taking photographs. Only use a flash for indoor close up photography. There is no need to have the flash on when taking a photo outside or when a subject is too far away for the flash to reach, because this will only drain batteries, and make one unable to use continuous shooting modes. When using a flash, one should use an ISO setting of 100-200. Many lenses have a reduced range of aperture as one increases the mm length of the lens (zoom in). For example, the standard lens that comes with a Canon 300D or 350D has a range of 18-55mm. When at 18mm, the largest the aperture can be is F/3.5. If one goes in to 24mm, the largest aperture possible is F/4.0. At about 30mm, the maximum is F/4.5. F/5.0 is the maximum for about 38mm. By the time one gets to 55mm, the largest possible aperture that I can use is F/5.6. Some lenses offer the same maximum aperture through the whole range of the lens. A lens that has F/2.8 throughout the entire length of the lens is the best that can be found, except these are sometimes even more expensive than an image stabilized lens. Canon makes a great lens that is both F/2.8 throughout it's entire 70-300mm range, and also image stabilized. The least that I could find this lens for is $1640. That price is just for the lens, with no camera included.

Overall, there are many different ways to ensure a clear, and properly exposed image. One can experiment with all of the different settings that I have explained to find the way that best works for him or her. Humans are smarter than the camera's automatic detection. When we program the camera, we can produce much better photographs.

Nolan's Photography Blog

Seattle Sunset

First Infrared Photographs

HOW TO TAKE A CLEAR AND PROPERLY EXPOSED PHOTOGRAPH - An essay that I wrote