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In the most familiar acuity test, a Snellen chart is placed at a standard distance: 6 metres. At this distance, the symbols on the line representing "normal" acuity subtend an angle of five minutes of arc, and the thickness of the lines and of the spaces between the lines subtends one minute of arc. This line, designated 6/6 (or 20/20), is the ...
The 645 format is nominally 6×4.5 cm, but actual frame measurements are 56×41.5 mm (2.20×1.63 in), [89] [90] which gives a crop factor (aka focal length multiplier) of 0.62 compared to 135 film. For comparison, a H system lens with a focal length of 80 mm using an H system film back would have the equivalent coverage of a lens with a focal ...
A 1951 USAF resolution test chart is a microscopic optical resolution test device originally defined by the U.S. Air Force MIL-STD-150A standard of 1951. The design provides numerous small target shapes exhibiting a stepped assortment of precise spatial frequency specimens. It is widely used in optical engineering laboratory work to analyze and ...
statvolt (CGS unit) statV. ≘ c ⋅ (1 μJ/A⋅m) = 299.792458V. volt (SI unit) V. The difference in electric potential across two points along a conducting wire carrying one ampere of constant current when the power dissipated between the points equals one watt. [ 32 ] = 1 V = 1 W/A = 1 kg⋅m2/ (A⋅s3) = 1 J/C.
For a complete list of all dimensions, see full list of units . { {Convert}} uses unit-codes, which are similar to, but not necessarily exactly the same as, the usual written abbreviation for a given unit. These unit-codes are displayed in column 3 of the following tables. These are accepted as input by { {convert}} as the second and third ...
Its size is 1.5 m × 2.1 m (5 ft × 7 ft). [13] According to the 2007 Guinness World Records, the largest published book in the world was The Little Prince printed in Brazil in 2007. Its size is 2.01 m × 3.08 m (6 ft 7 in × 10 ft 1 in). [14]
The people of Ancient Egypt stood around 167 cm (5 ft 6 in) for males and 157 cm (5 ft 2 in) for females. [60] The Ancient Greeks averaged 166 cm (5 ft 5 in) for males and 154 cm (5 ft 1 in) for females. The Romans were slightly taller, with an average height of 169 cm (5 ft 7 in) for males and 158 cm (5 ft 2 in) for females. [61]
Medium-format cameras typically have format designated by nominal sizes in centimeters (6×6, 6×7, 6×9, 6×4.5), but these numbers should not be interpreted as exact in computing aspect ratios. For example, the usable height of 120-format roll film is 56mm, so a width of 70mm (as in 6×7) yields an aspect ratio of 4:5 — ideal for enlarging ...