Aperture

An adjustable opening in a camera lens that regulates how much light reaches the image sensor or film. Its diameter also affects depth of field and image sharpness.

Iris diaphragm: An overlapping set of blades that forms a variable circular opening in an optical system. Its blades move to enlarge or shrink the aperture.
Bokeh: The visual character of out-of-focus regions in a photograph. Aperture shape and size influence the appearance of blurred highlights.
Shutter: A camera mechanism that controls how long light reaches the image sensor or film. It controls exposure duration, while aperture controls the opening’s size.
Focal length: The distance that characterizes how strongly an optical system converges or diverges light. It combines with entrance-pupil diameter to determine the f-number.
F-number: The ratio of a lens’s focal length to its entrance-pupil diameter. It expresses aperture size in a standardized exposure scale.
Shutter speed: The duration for which a camera sensor or film is exposed to light. Photographers balance it against aperture to achieve a desired exposure.
Field stop: An optical opening that limits the extent of the image field visible through an instrument. Unlike the aperture stop, it primarily limits field of view rather than light-cone width.
Image sensor: An electronic component that converts incoming light into image data. The aperture regulates the light that ultimately reaches this component.
Exposure triangle: A photography model relating aperture, shutter speed, and ISO as controls of exposure. Aperture is one of its three interacting exposure controls.
ISO: A camera setting that determines the image signal’s amplification or sensitivity scale. It offers another exposure adjustment when aperture is constrained.

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