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).

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

phot

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

McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.