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There is no precise definition of the term, but lenses marketed as "standard zoom" usually cover a range of at least 30mm to 70mm in terms of 35mm equivalent focal length with an optical zoom ratio of 2.5× (e.g. 28-70mm) to 5× (e.g. 24-120mm) — the most common being 3× (e.g. 24-70mm). [1]
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 ...
A 50 mm (focal length) lens on an APS-C image sensor format (crop factor 1.6) images a slightly smaller field of view than a 70 mm lens on a 35 mm sensor format camera (full frame sensor). A 80 mm lens (1.6 × 50 mm = 80 mm) with a full frame camera gives the same field of view as this 50 mm lens and APS-C sensor format combination produces.
Optical format is a hypothetical measurement approximately 50% larger than the true diagonal size of a solid-state photo sensor.The use of the optical format means that a lens used with a particular size sensor will have approximately the same angle of view as if it were to be used with an equivalent-sized video camera tube (an "old-fashioned" TV camera).
Other measures are also used; see table of sensor formats and sizes below. Lenses produced for 35 mm film cameras may mount well on the digital bodies, but the larger image circle of the 35 mm system lens allows unwanted light into the camera body, and the smaller size of the image sensor compared to 35 mm film format results in cropping of the ...
Zoom lenses are often described by the ratio of their longest to shortest focal lengths. For example, a zoom lens with focal lengths ranging from 100 mm to 400 mm may be described as a 4:1 or "4×" zoom. Typical zoom lenses cover a 3.5× range, for example 24–90 mm (standard zoom) or 60–200 mm (telephoto zoom).
The alternative Super series, denoted SnR, nR Plus or nR+, has an aspect ratio of 3∶2 (or as close as possible) and thus provides a better fit for standard 135 film (35 mm) at sizes of 8 inches or above. 5R is twice the size of a 2R print, 6R twice the size of a 4R print and S8R twice the size of 6R. 4D/6D is a newer size for most consumer ...
The number 1/1730 derives from a circle of confusion diameter of 0.025 mm on a full-frame 35 mm film format, with diagonal size about 43.25 mm (43.25/0.025 is 1730). The CoC size of 0.025 mm for this format appears in Jacobson's Photographic Lenses Tutorial, [ 1 ] and the 1730 in his 1996 Photographic Lenses FAQ. [ 2 ]