Phot

phot

[fōt]

(optics)

A unit of illumination equal to the illumination of a surface, 1 square centimeter in area, on which there is a luminous flux of 1 lumen, or the illumination on a surface all points of which are at a distance of 1 centimeter from a uniform point source of 1 candela. Also known as centimeter-candle (deprecated usage).

Phot

 

an archaic unit of illumination equal to the illumination of a surface, 1 cm² in area, over which a luminous flux of 1 lumen is uniformly distributed. Symbol, ph. In conjunction with the phot, the unit called the radphot (symbol, rph) was used to measure the luminous exitance of a luminous surface. After the introduction of All-Union State Standard (GOST) 7932–56, “Photometric Units”, the SI unit called the lux (symbol, lx) was adopted as the unit of illumination, and the lumen per square meter (symbol, lm/m²) was adopted as the unit of luminous exitance. Equivalents: 1 ph = 10⁴ lx; 1 rph = 10⁴ lm/m².

phot

A unit of illumination equal to 1 lumen per square centimeter. Abbr. ph.