As stated in the Photography lessons introduction, there are 2 settings that control how your picture is exposed: Aperture and Shutter Speed.

Some of you may not understand what I mean by “exposure”, so I'll take a minute to define that word. Exposure is how light or dark a picture is. If a photo is “over exposed”, it was exposed to too much light, and looks washed out or too bright. “Under exposed” means the picture turned out darker than intended. When a picture is “exposed correctly”, it means that it came out as light or dark as you wanted it to.

So, like I was saying, 2 things effect exposure: aperture and shutter speed. In this lesson we'll be talking about aperture.

Aperture controls the depth of field or how much of the picture will be in focus. If you're taking a portrait, for example, and the background is cluttered or generally not attractive, you'd want set the aperture to a small number to blur the background. If you're taking a landscape shot, you want everything, including the background, to be in focus, so this time you'd pick an aperture with a large number to keep the background sharp.

An example of a picture taken with a small-numbered aperture (f/2.8):

CREATOR: gd-jpeg v1.0 (using IJG JPEG v62), quality = 75

An example of a picture take with a large-numbered aperture (f/6.3):

Created by AccuSoft Corp.

Apertures are written in f-stops as shown in the example pictures above. The apertures that are available to you will very depending on the camera and lens you are using, but they typically range from f/2 to F/6.3 (or f/16 for non-zoom lenses).

Got it? Good. -Now's the time to pull out your manual and find out how to set your camera to “Aperture-Priority” mode. On most Canon's this will be indicated by the letters “Av” on the mode dial. On Nikons, it's the “A” on the mode dial. “Aperture Priority” mode allows you to set the aperture yourself, then the camera will automatically choose the proper shutter speed to match it so that the exposure is as it would be in “Auto” mode.

So, set your camera to Aperture-Priority mode, then go find a ruler or tape measure to photograph. Lay the yard stick or tape measure out on a table so you can photograph it long-ways and at a slight angle so that you can see the whole thing. Start with an aperture of f/2.8 (or the lowest setting your camera will allow you to take a picture with), focus on say the 3-inch mark, and take a picture. (Refer to your manual to find out how to change the aperture value.) Then go up one setting, take another picture (focusing on the same mark), and continue until you reach the highest-numbered aperture the camera will allow. When you're done, download the pictures (or have them developed) to see the difference the aperture settings make. (INSERT EXAMPLES HERE)

Small-numbered apertures are good for eliminating background clutter and focusing attention on things. Whatever is in-focus is what people will concentrate on when looking at a picture. For portraits, an aperture that'll allow the entire face to be in-focus can be used, or you can choose an even smaller number if you just want the eyes to be in focus, with a softer look for the rest of the skin. This is especially nice with infants, but keep in mind that your margin of error when focusing gets smaller and smaller along with your aperture-number. You won't want to use an extremely small aperture-number if your subject is moving!


Experiment with controlling depth of field (often abbreviated as “DOF”) by taking pictures of a subject infront of a background at different apertures. Make notes as you take your pictures so you'll remember what your settings were when you go to review them. Make note of how the different aperture numbers effect your photos and think about the artistic value of being able to control your depth of field. When you have the idea of aperture down, move onto Lesson 2 -About Shutter Speed.


about_aperture.txt · Last modified: 2010/06/16 13:42 (external edit)
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