A: Aperture Priority Mode
A on the Mode dial refers to Aperture Priority mode. It is one of the most useful and popular of the professional modes. Aperture Priority mode is considered a semiautomatic mode because it allows you to control two factors of exposure while the camera adjusts for the other. You choose the aperture value and the ISO, and the camera chooses the shutter speed.
This is one of my favorite modes because the aperture value largely 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 factor that controls how much of your image is in focus. If you want to isolate a subject from the background, such as when shooting a portrait, you can use a large aperture (low f-stop number) 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, then using a small aperture (high f-stop number) will render the greatest possible depth of field.
When to use Aperture Priority (A) mode
When shooting portraits or wildlife (Figure 4.3)
Figure 4.3 A large aperture (low f-stop number) and a longer focal length create a very blurry background to emphasize the subject.
ISO 100 • 1/200 sec. • f/5.6 • 45mm lens
When bracketing images for HDR photography (Figure 4.4)
Figure 4.4 I combined three different exposures of the same scene to create this HDR image. Combining multiple exposures can help capture the entire dynamic range of a scene. It is best to keep the aperture value consistent while adjusting the shutter speed for different exposures.
ISO 800 • f/11 • multiple shutter speeds • 16–35mm lens
When shooting landscape photography, which often benefits from a large depth of field (Figure 4.5)
Figure 4.5 The smaller aperture setting (higher f-stop number) brings sharpness to near and far objects.
ISO 200 • 1/400 sec. • f/8 • 35–100mm lens
We have established that Aperture Priority (A) mode is highly useful in controlling the depth of field in your image. 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 a properly exposed image. 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 to reduce hand shake and blurriness in the final picture. 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 allows the shutter stay open longer.
Setting up and shooting in A mode
- Turn your camera on and then turn the Mode dial to align the A with the indicator line.
To select your ISO on the GX7, press the ISO button (), rotate the Rear dial to the desired setting, and press the Rear dial to select (the ISO selection will appear in the electronic viewfinder and the rear LCD panel).
On the GM1, press the Fn1 button we assigned to ISO in Chapter 1. Rotate the Control dial to the desired setting and press MENU/SET.
- Turn the Front dial (GM1: Control dial) to select the aperture value (f-stop). Turn the dial to the left for a larger aperture (lower f-stop number) and to the right for a smaller aperture (higher f-stop number).
- Point the camera at your subject, and then activate the camera meter by depressing the shutter button halfway.
- View the exposure information in the electronic viewfinder or on the rear LCD panel.
- Press and turn the Rear dial (GM1: , then Control dial) to change the exposure compensation to make the image brighter or darker.