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In some contexts, especially in photography and astronomy, aperture refers to the opening diameter of the aperture stop through which light can pass. For example, in a telescope, the aperture stop is typically the edges of the objective lens or mirror (or of the mount that holds it). One then speaks of a telescope as having, for example, a 100 ...
Half-stop steps are used on some cameras. Usually the full stops are marked, and the intermediate positions click but are not marked. As an example, the aperture that is one-third stop smaller than f /2.8 is f /3.2, two-thirds smaller is f /3.5, and one whole stop smaller is f /4. The next few f-stops in this sequence are:
Increasing f-stop decreases the aperture of a lens. In photography, stopping down refers to increasing the numerical f-stop number (for example, going from f / 2 to f / 4), which decreases the size (diameter) of the aperture of a lens, resulting in reducing the amount of light entering the iris of a lens. [1] [2]: 112
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.
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.
f-number, f-stop. The numerical value of a lens aperture. The ratio of the focal length of the lens divided by its effective aperture diameter. [4] FF: Full frame, where the image sensor is approximately the same size as a 35 mm film: 36 × 24 mm. FP: Focal plane.
Telecentricity is not a property of the lenses inside the compound lens but is established by the location of the aperture stop in the lens. The aperture stop selects the rays that are passed through the lens and this specific selection is what makes a lens telecentric. If a lens is not telecentric, it is either entocentric or hypercentric ...
For example: On a sunny day at ISO 100 ("100 speed film"), the aperture is set to f /16 and the shutter speed (i.e. exposure time) to 1 / 100 or 1 / 125 [2] seconds (on some cameras 1 / 125 second is the closest available setting to 1 / 100 second).