Relative aperture
The measurable diameter of the diaphragm divided by the focal length of the lens in use and expressed in terms of "f" numbers, marked on the lens barrel.
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Relative Aperture
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Relative aperture.
Numerical expression of effective aperture, also known as f-number. Obtained by dividing focal length by diameter of effective aperture.
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relative aperture:
Also known as the f-stop, this is the diameter of the aperture of a camera divided by the focal length of the lens.
resample: ...
The relative aperture is specified as an f-number, the ratio the lens focal length to its effective aperture diameter. A small f-number like f/2.
N is the relative aperture (f-stop)
and t is the exposure time (shutter speed).
so, for example, an exposure of 1/250s at f8 is an EV of log2(8*8*250) = 14 (to 2 figures, actually nearer 13.96578...) ...
If the lens were focused at other than infinity, f/8 would then be the relative aperture. In the study of the relationship between aperture and image brightness, the term relative aperture is used frequently.
Also can be explained as numerical expression of the relative aperture of a lens at its different stops; equal to the focal length divided by the effective aperture of the lens opening and written in various forms, such as f/8, f8, 1: 8, etc.
f/number or f/stop The numerical expression of the relative aperture of a lens. Each f/number is 1.4 times larger than the preceding one, and each number indicates a halving or doubling of the amount of light allowed to pass through the lens.
The relative aperture is calibrated in f-numbers, being the diameter of the beam of light allowed to pass through the lens, divided into its focal length.Widest relative apertures therefore have the lowest f-numbers.
55 mm lens ÷ effective aperture 5 mm = relative aperture f11.
All lenses stopped down to the same f number should transmit the same amount of light.
There's no really simple "rule of thumb" that will tell you whether relative aperture (f-stop) or absolute aperture (size of the aperture in mm) will be most important in determining the degree of blurring at a given distance behind (or in front of) ...
F-stop also known as f-number, this is the measure used to determine the relative aperture size of a lens. It is calculated by dividing the diameter of the aperture opening by the focal length of the lens.
F/number - the designation for a relative aperture of a lens
Bellows - folding portion in some cameras which connects the lens to the camera body
Focal plane - position in the camera where the film is ...
This value, the relative aperture of a lens, describes the amount of light that a lens lets in.
Expressing apertures as fractions of the focal length is more practical for photographers than using absolute aperture sizes. These "relative apertures" are called f-numbers or f-stops.
 See also: Aperture, Focal, Meter, Lens, Light
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