Av: Aperture Priority Mode
You wouldn't know it from its name, but Av mode is one of the most useful and popular modes in the Creative zone. Av stands for Aperture Value and, like Time Value, it's another term that you'll never hear a photographer toss around. The mode, however, is one of my personal favorites, and I believe that it will quickly become one of yours, as well. Av, more commonly referred to as Aperture Priority mode, is also deemed a semiautomatic mode because it allows you to once again control one factor of exposure while the camera adjusts for the other.
Why, you may ask, is this one of my favorite modes? It's because the aperture of your lens dictates depth of field. Depth of field, along with composition, is a major factor in how you direct attention to what is important in your image. It is the controlling factor of how much area in your image is sharp. If you want to isolate a subject from the background, such as when shooting a portrait, you can use a large aperture to keep the focus on your subject and make both the foreground and background blurry. If you want to keep the entire scene sharply focused, such as with a landscape scene, then using a small aperture will render the greatest amount of depth of field possible.
When to Use Aperture Priority (Av) Mode
- When shooting portraits or wildlife (Figure 4.7)
Figure 4.7 A large aperture created a very blurry background so all the emphasis was left on the subject.
- When shooting most landscape photography (Figure 4.8)
Figure 4.8 The smaller aperture setting brings sharpness to near and far objects.
- When shooting macro, or close-up, photography (Figure 4.9)
Figure 4.9 Small apertures give more sharpness in macro images.
- When shooting architectural photography, which often benefits from a large depth of field (Figure 4.10)
Figure 4.10 A wide-angle lens combined with a fairly small aperture makes for a lot of depth of field.
So we have established that Aperture Priority (Av) mode is highly useful in controlling the depth of field in your image. But it's also pivotal in determining the limits of available light that you can shoot in. Different lenses have different maximum apertures. The larger the maximum aperture, the less light you need in order to achieve an acceptably sharp image. You will recall that, when in Tv mode, there is a limit at which you can handhold your camera without introducing movement or hand shake, which causes blurriness in the final picture. If your lens has a larger aperture, you can let in more light all at once, which means that you can use faster shutter speeds. This is why lenses with large maximum apertures, such as f/1.4, are called "fast" lenses.
On the other hand, bright scenes require the use of a small aperture (such as f/16 or f/22), especially if you want to use a slower shutter speed. That small opening reduces the amount of incoming light, and this reduction of light requires that the shutter stay open longer.
Setting Up and Shooting in Av Mode
- Turn your camera on and then turn the Mode dial to align the Av with the indicator line.
- Select your ISO by pressing the ISO button on the top of the camera, and then turning the Main dial.
- Point the camera at your subject and then activate the camera meter by depressing the shutter button halfway.
- View the exposure information in the bottom area of the viewfinder or by looking at the rear display panel.
- While the meter is activated, use your index finger to roll the Main dial left and right to see the changed exposure values. Roll the dial to the right for a smaller aperture (higher f-stop number) and to the left for a larger aperture (smaller f-stop number).