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For full-frame 35 mm-format cameras, the diagonal is 43 mm and a typical "normal" lens has a 50 mm focal length. A lens with a focal length shorter than normal is often referred to as a wide-angle lens (typically 35 mm and less, for 35 mm-format cameras), while a lens significantly longer than normal may be referred to as a telephoto lens ...
A 100 mm focal length f /4 lens has an entrance pupil diameter of 25 mm. A 100 mm focal length f /2 lens has an entrance pupil diameter of 50 mm. Since the area is proportional to the square of the pupil diameter, [6] the amount of light admitted by the f /2 lens is four times that of the f /4 lens.
35 mm equivalent focal lengths are calculated by multiplying the actual focal length of the lens by the crop factor of the sensor. Typical crop factors are 1.26× – 1.29× for Canon (1.35× for Sigma "H") APS-H format, 1.5× for Nikon APS-C ("DX") format (also used by Sony, Pentax, Fuji, Samsung and others), 1.6× for Canon APS-C format, 2× for Micro Four Thirds format, 2.7× for 1-inch ...
Notice that the shorter the focal length and the larger the angle of view, perspective distortion and size differences increase. Lenses are often referred to by terms that express their angle of view: Fisheye lenses, typical focal lengths are between 8 mm and 10 mm for circular images, and 15–16 mm for full-frame images. Up to 180° and beyond.
The crop factor is sometimes referred to as the focal length multiplier ("Film") since multiplying a lens focal length by the crop factor gives the focal length of a lens that would yield the same field of view if used on the reference format. For example, a lens with a 50 mm focal length on an imaging area with a crop factor of 1.6 with ...
Instead, the angular aperture of a lens (or an imaging mirror) is expressed by the f-number, written f /N, where N is the f-number given by the ratio of the focal length f to the diameter of the entrance pupil D: =. This ratio is related to the image-space numerical aperture when the lens is focused at infinity. [3]
Curvature radius of lens/mirror r, R: m [L] Focal length f: m [L] Quantity (common name/s) (Common) symbol/s Defining equation SI units Dimension Lens power P
Diagram illustrating the flange focal length of an SLR–type and a mirrorless–type camera. For an interchangeable lens camera, the flange focal distance (FFD) (also known as the flange-to-film distance, flange focal depth, flange back distance (FBD), flange focal length (FFL), back focus [1] or register, depending on the usage and source) of a lens mount system is the distance from the ...