Aperturepriority

Aperture priority is a camera exposure mode in which the photographer selects the aperture (f-number) and the camera automatically selects a corresponding shutter speed to achieve a correct exposure based on the scene’s metering. Some cameras also offer auto ISO in this mode, allowing the overall exposure to adapt while the chosen aperture remains fixed.

The primary function of aperture priority is to control depth of field. A wide aperture (low f-number, such as f/1.8) yields a shallow depth of field with strong subject isolation, while a narrow aperture (high f-number, such as f/16) increases depth of field and keeps more of the scene in focus. Aperture also influences overall sharpness through diffraction at very small values, where image softness can occur.

Aperture priority is commonly used when depth of field is the main creative concern, such as portraits where background blur is desirable or landscapes where foreground to background sharpness is important. It is less suited to rapidly changing lighting or fast action where controlling shutter speed is critical, though auto ISO can help maintain exposure without sacrificing the chosen aperture.

Compared with shutter priority, where the photographer selects the shutter speed, aperture priority gives priority to depth of field. Exposure compensation can still be used to adjust brightness if the meter’s exposure is biased by the scene, and in manual exposure you have full control over both aperture and shutter.

Practical tips include checking the histogram after shooting, avoiding excessive diffraction by not stopping down too far, using exposure compensation for tricky lighting such as backlit scenes, and enabling auto ISO if maintaining a specific depth of field is important while letting exposure adapt.