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Diagram of decreasing apertures, that is, increasing f-numbers, in one-stop increments; each aperture has half the light-gathering area of the previous one.. An f-number is a measure of the light-gathering ability of an optical system such as a camera lens.
Thus it is also called a stop (an aperture stop, if it limits the brightness of light reaching the focal plane, or a field stop or flare stop for other uses of diaphragms in lenses). The diaphragm is placed in the light path of a lens or objective , and the size of the aperture regulates the amount of light that passes through the lens.
Hardware and software ("firmware"), built into the camera, measures luminance of the subject and automatically sets shutter speed, lens aperture or sensitivity; this also allows the camera to set the aperture for manual lenses fixed with an AE chip. [4] AE-L or AEL: Automatic exposure lock. Technology for holding an exposure setting from one ...
Larger stops can cause the light intensity reaching the film or detector to fall off toward the edges of the picture, especially when, for off-axis points, a different stop becomes the aperture stop by virtue of cutting off more light than did the stop that was the aperture stop on the optic axis. The stop location determines the telecentricity ...
A the relative aperture (f-number) T the exposure time ("shutter speed") in seconds [2] A v and T v represent the numbers of stops from f /1 and 1 second, respectively. Use of APEX required logarithmic markings on aperture and shutter controls, however, and these never were incorporated in consumer cameras.
The Waterhouse stop or Waterhouse diaphragm is an interchangeable diaphragm with an aperture (hole) for controlling the entry of light into a camera. A thin piece of metal (the diaphragm) is drilled with a hole (the aperture); a set of these with varying hole sizes makes up a set of Waterhouse stops, corresponding to what today we call f-stops ...
In photography, the size of the entrance pupil (rather than the size of the physical aperture stop) is used to calibrate the opening and closing of the diaphragm aperture. The f-number (also called the ' relative aperture ' ), N , is defined by N = f / E N , where f is the focal length and E N is the diameter of the entrance pupil. [ 2 ]
Single lens imaging with the aperture stop. The exit pupil is the image of the aperture stop formed by the optics behind it, and the location and size of the pupil are determined by chief rays and marginal rays. The image side of the lens of an SLR camera; the exit pupil is the light area in the middle of the lens.