Probably the mode most widely used by professional photographers, Aperture Priority is one of my personal favorites, and I believe that it will quickly become one of yours. 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 (Figure 4.11).
Why 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 matters 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, 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 (A) mode
- When shooting portraits or wildlife (Figure 4.12)
- When shooting most landscape photography (Figure 4.13)
- When shooting macro, or close-up, photography (Figure 4.14)
- When shooting architectural photography, which often benefits from a large depth of field (Figure 4.15)
F-stops and aperture
As discussed earlier, the numeric value of your lens aperture is described as an f-stop. The f-stop is one of those old photography terms that, technically, relates to the focal length of the lens (e.g., 200mm) divided by the effective aperture diameter. These measurements are defined as “stops” and work incrementally with your shutter speed to determine proper exposure. Older camera lenses used one-stop increments to assist in exposure adjustments, such as 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, and 22. Each stop represents about half the amount of light entering the lens iris as the larger stop before it. Today, most lenses don’t have f-stop markings, since all adjustments to this setting are performed via the
camera’s electronics. The stops are also now typically divided into 1/3-stop increments to allow much finer adjustments to exposures, as well as to match the incremental values of your camera’s ISO settings, which are also adjusted in 1/3-stop increments.
I strongly recommend knowing your lens’s aperture rating. Every lens has a marking on it with a number; f/1.4, f/2.8, or f/5.6 are all very common maximum aperture sizes. This number simply means the largest aperture your lens supports is f/1.4, f/2.8, or f/5.6, respectively. The D7000 kit ships with a standard 18–105mm lens with an f/3.5–f/5.6 variable maximum aperture.
Knowing the limits of your lens aperture is crucial when using Aperture Priority. As a general rule, the lower the number on the lens, the “faster” it is (because it allows more light in to expose the image, thus reducing the amount of shutter time) and the sharper the image is. Typically, fast lenses are heavier and more expensive, but well worth the investment if you find yourself shooting in low light conditions. The larger the aperture is, the better the exposure without having to increase ISO and introduce digital noise.
See page 269 in your Nikon D7000 owner’s manual to determine the maximum aperture of your lens.
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 Aperture Priority mode
- Turn your camera on and then turn the Mode dial to align the A with the indicator line.
- Select your ISO by pressing and holding the ISO button on the back left of the camera while rotating the main Command dial with your thumb.
- The ISO will appear on the top display. Choose your desired ISO, and release the ISO button on the left to lock in the change.
- 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 thumb to roll the 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 (lower f-stop number).
Zoom lenses and maximum apertures
Some zoom lenses (like the 18–105mm kit lens) have a variable maximum aperture. This means that the largest opening will change depending on the zoom setting. In the example of the 18–105mm zoom, the lens has a maximum aperture of f/3.5 at 18mm and only f/5.6 when the lens is zoomed out to 105mm.