A camera’s aperture setting controls the area over which light can pass through your camera lens. It is specified in terms of an f-stop value, which can at times be counter-intuitive, because the area of the opening increases as the f-stop decreases. In photographer slang, when someone says they are “stopping down” or “opening up” their lens, they are referring to increasing and decreasing the f-stop value, respectively.

lenses_aperture

 

Technical Note: With many lenses, their light-gathering ability is also affected by their transmission efficiency, although this is almost always much less of a factor than aperture. It’s also beyond the photographer’s control. Differences in transmision efficiency are typically more pronounced with extreme zoom ranges. For example, Canon’s 24-105 mm f/4L IS lens gathers perhaps ~10-40% less light at f/4 than Canon’s similar 24-70 mm f/2.8L lens at f/4 (depending on the focal length).

How it Appears: A camera’s aperture setting is what determines a photo’s depth of field (the range of distance over which objects appear in sharp focus). Lower f-stop values correlate with a shallower depth of field:

Wide Aperture f/2.0 - low f-stop number shallow depth of field

Wide Aperture
f/2.0 – low f-stop number
shallow depth of field

Narrow Aperture f/16 - high f-stop number large depth of field

Narrow Aperture
f/16 – high f-stop number
large depth of field

Different aperture size

Different aperture size

 

Categories: Technical

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