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Concepts in Photography
Aperture
The aperture is one of the three factors that determine the exposure. The
aperture housing contains thin, metal plates that open and close to let
light through the aperture and into the camera. The size of the aperture
is related to the amount of light: a larger aperture allows more light and a
smaller aperture allows less light.
Aperture sizes
Minimum aperture
Medium aperture
Aperture opened slightly
Maximum aperture
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 ne-tune the
amount of light by subdividing exposure values into 1/2, 1/3 EV, and so on.
+1 EV
-1 EV
F1.4
F2
F2.8
Exposure Value Steps
F4
F5.6
F8
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