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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. To obtain the same photographic exposure, the exposure time must be reduced by a factor of four. A 200 mm focal length ...
Grain size (or particle size) is the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials. This is different from the crystallite size, which refers to the size of a single crystal inside a particle or grain. A single grain can be composed of several ...
From 1.0 through 2.95 mm, sizes are defined as follows, where N is an integer from 10 through 29: N · 0.1 mm; N · 0.1 + 0.05 mm; From 3.0 through 13.9 mm, sizes are defined as follows, where N is an integer from 30 through 139: N · 0.1 mm; From 14.0 through 25.0 mm, sizes are defined as follows, where M is an integer from 14 through 25: M ...
Sizes are often expressed as a fraction of an inch, with a one in the numerator, and a decimal number in the denominator. For example, 1/2.5 converts to 2/5 as a simple fraction, or 0.4 as a decimal number. This "inch" system gives a result approximately 1.5 times the length of the diagonal of the sensor.
37 mm kan M/98B (Finspång 37 mm naval gun L/39 model 1901) Sweden-Norway. 1900s - Cold War. 38.1 mm (1.50 in) 38 mm kan M/84 (Nordenfelt 1½In fast shooting naval gun L/43 model 1884) Sweden-Norway. 1880s - World War I. 40 mm (1.6 in) 40 mm ubakan m/32 (Bofors 40 mm submarine automatic gun L/43 model 1932)
5.75 in × 3.25 in × 8 in (146.1 mm × 82.55 mm × 203 mm). This smaller form factor, first used in an HDD by Seagate in 1980, was the same size as full-height 51⁄4 -inch-diameter (130 mm) FDD, 3.25-inches high. This is twice as high as "half height"; i.e., 1.63 in (41.4 mm). Most desktop models of drives for optical 120 mm disks (DVD, CD ...
The centimetre (SI symbol: cm) is a unit of length in the metric system equal to 10−2 metres ( 1 100 m = 0.01 m). To help compare different orders of magnitude, this section lists lengths between 10 −2 m and 10 −1 m (1 cm and 1 dm). 1 cm – 10 millimetres. 1 cm – 0.39 inches. 1 cm – edge of a square of area 1 cm 2.
A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or submultiple of the unit. All metric prefixes used today are decadic. Each prefix has a unique symbol that is prepended to any unit symbol. The prefix kilo-, for example, may be added to gram to indicate multiplication by one thousand: one kilogram ...