Beyond Auto Mode: A Guide to Taking Control of Your Photography

Chapter 7: APERTURE PRIORITY

Aperture priority, denoted as “AV” (aperture value) or “A” on your dial, enables you to control the amount of light coming in through your lens (aperture), while the camera chooses the shutter speed based on its internal formula for correct exposure and the built-in light meter reading.

Put another way, you choose your ISO and your aperture while the camera chooses the shutter speed. Remember, though, your camera wants you to have a balanced exposure—and you may not end up with the exposure you intended.

FIGURE 7-1 Aperture priority is indicated as A or AV on your camera dial.

In Chapter 3 we learned that aperture controls two things:

1. The amount of light coming in our lens (via the size of the lens opening)

2. The depth of field

A larger aperture (like f/2.8) lets in more light and gives us a shallower depth of field. A smaller aperture (like f/16) lets in less light and has an extended or deeper depth of field.

With that in mind, you might choose AV/A mode when you want to ensure a specific and consistent depth of field in your images. If you know you want to create a certain look via depth of field and you know what ISO you should use, but you are uncertain what the shutter speed should be, using AV is a quick way to determine the ...