Concepts in Photography
172
Aperture
The aperture, a hole that controls the amount of light that enters the camera, is one of the
three factors that determine the exposure. The aperture housing contains thin and metal
plates that open and close to let light through the aperture and into the camera. The size
of the aperture is closely related to the brightness of a photo: the larger the aperture, the
brighter the photo; the smaller the aperture, the darker the photo.
Darker photo
(aperture opened slightly)
Brighter photo
(aperture opened wide)
The size of the aperture is represented by a value known as an F-number. The f-number
represents the focal length divided by the diameter of the lens. For example, if a lens with a
50 mm focal length has an f-number of F2, the diameter of the aperture is 25 mm. (50 mm/25
mm=F2) The smaller the f-number, the greater the size of the aperture.
The opening in the aperture is described as the exposure value (EV). Increasing the exposure
value (+1 EV) means the amount of light doubles. Decreasing the exposure value (-1 EV)
means the amount of light halves. You can also use the exposure compensation feature to
fine-tune the amount of light by subdividing exposure values into 1/2, 1/3 EV, and so on.
+1 EV
F1.4 F2 F2.8 F4 F5.6 F8
-1 EV
Exposure value steps