A: Aperture Priority Mode
You wouldn’t know it from its name, but Aperture Priority mode is one of the most useful and popular modes in DSLR photography. Aperture Priority is one of my favorite modes, and I believe that it will quickly become one of yours as well. Aperture Priority is deemed a semi-automatic mode because it allows you to once again control one factor of exposure while the camera adjusts for another.
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 element in how you direct attention to what is important in your image. It is the controlling factor when determining how much of 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 your emphasis is on keeping the entire scene sharply focused, such as with a landscape scene, then using a small aperture will render the greatest depth of field possible.
When to use Aperture Priority mode
When shooting portraits or wildlife (Figure 4.7)
Figure 4.7 A large aperture created a very blurry background, so all the emphasis is 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 A small aperture was used to capture the smiling faces of my bees as they emerged from the hive.
When shooting architectural photography, which often benefits from a large depth of field (Figure 4.10)
Figure 4.10 I like to use smaller apertures for architectural shots to keep everything in focus.
So we have established that Aperture Priority (A) 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, or f-stop, the less light you need to achieve an acceptably sharp image. You will recall that in Shutter Priority 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, then 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 (Figure 4.11). That small opening reduces the amount of incoming light, and this reduction of light requires that the shutter stay open longer.
Figure 4.11 A wide-angle lens combined with a small aperture added to the depth of field. It also created the need for a long shutter speed, which helped add fluidity to the falling water.
Setting up and shooting in Aperture Priority mode
- Turn your camera on. Press the Mode dial release lock, and turn the Mode dial to align the A with the indicator line.
- Set your ISO by pressing the ISO button; select the appropriate setting by looking at the ISO readout on the control panel or by pressing the Info button on the back of the camera and looking at the info display on the rear LCD monitor.
- Once your ISO is set, 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 in the control panel.
- While the meter is activated, use your index finger to roll the Sub-command 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).