Semi-automatic modes give you more creative control over the various elements of your photos than full auto, but without throwing you into full manual mode. Choose what factor you wish to control — depth of field, shutter speed — and pick a semi-automatic mode that takes care of the rest.
Aperture Priority Mode
In Aperture Priority mode, you set the aperture and the camera determines the rest of the exposure settings automatically. Aperture priority mode is useful for creatively using depth of field or choosing an aperture that is optimal for low-light shooting (or blocking out ambient light) without worrying about the shutter speed.
Examples:
- Choose a low f number for a shallow depth of field, such as 2.8 or 1.4. This will give you a blurry, out-of-focus background.
- Choose a high f number such as 10, 16 or 22 for a deep depth of field that will put much more of your subject in focus. This is often useful for landscape photos.
- Choose a low f number — which corresponds to a wider aperture — to shoot hand-held in low light. The wider aperture allows more light to hit the sensor, enabling you to use a shutter speed fast enough to photograph a person or eliminate blur resulting from shaking hands.
Program Mode
In Program mode, nearly all of the camera’s settings are determined automatically. The camera chooses the aperture and the shutter speed, and you are in charge of framing your subject.
Examples:
- You want to concentrate on thoughtfully framing your photographs, so you set your camera to program mode, choose an appropriate ISO and work on your composition techniques without worrying about specific settings.
Shutter Priority Mode
In Shutter Priority mode, you set the shutter speed and the camera determines the rest of the exposure settings automatically. An example of a situation where this is applicable is sports — use your DSLR’s shutter priority mode to set a fast motion-stopping shutter speed, and let the camera automatically choose the other necessary settings for a good exposure.
Examples:
- Choose a fast shutter speed such as 1/1000 of a second to freeze the motion of a fast-moving athlete.
- Choose a slower shutter speed to create motion blur, e.g. photograph fast-moving taxi cabs at night as a streaks of yellow.
Beyond shutter speed and aperture
In these various semi-automatic modes, there are other settings beyond exposure that are also left up to the photographer. It is often up to you to choose an appropriate ISO number, however many newer DSLRs also offer auto-ISO. Focusing and metering are also important settings — you choose which AF mode to use, and which mode to use in order to meter light in the frame.
Using flash
A camera that has been set to one of these semi-automatic modes usually will not fire the flash unless you specifically ask the camera to do so — either by manually activating or popping up your built-in flash, or attaching and turning on an external flash
Photo by nate steiner used under a Creative Commons license.