What Does the A on My Camera Mean?

In previous posts, I've briefly described what the letters P (Program mode) and S (Shutter Priority mode) on the exposure dial mean. In this post, I explain the letter "A," which stands for "Aperture Priority" exposure mode. Canon cameras use "Av" for "Aperture Value," which means the same thing. The aperture is the size of the lens opening, designated by an f/number.

f/2.8, 1/500 second, ISO 100

Aperture Priority exposure mode lets you control how sharp or blurred the background is behind your subject. If you select a small aperture number such as f/4, the background becomes out of focus. If you choose a big aperture number such as f/16, the background appears sharper. Because the camera is adjusting the shutter speed for the best exposure, you don't have control over the amount of time the shutter is open.

f/22, 1/60 second, ISO 400

You can still adjust the ISO (sensitivity) setting when you are working in Aperture Priority mode. When you want a blurred background, you may need to use a low ISO number to prevent the scene from becoming overexposed. If you want a sharp background, you might need to use a higher ISO number to keep subjects such as blowing flowers or leaves sharp. If your model has an Auto ISO setting, you can let the camera decide.

You can use flash with Aperture Priority exposure, but it won't come on automatically. If your aperture setting is too high, such as f/11 or higher, you may not get much light from the built-in flash.

Learn about Aperture Priority mode and other camera controls in my one-day Getting to Know Your Digital SLR Camera class on June 9, 2018, in Missoula, Montana. Click here to register online.