phot Physics.
(fəʊt)
[a. F. phot, f. Gr. ϕῶς, ϕωτ- light.]
† a. A unit of the product of illumination and duration, equal to one lux maintained for one second. Obs.
| 1894 tr. A. Blondel in Electrician 28 Sept 634/2 Some years ago the photographers..established under the presidency of eminent savants (MM. Abney, Cornu, Janssen, Sébert, Violle, &c.), a unit of time-illumination (illumination) specially applicable to photography, the ‘phot’. |
b. A unit of illumination equal to one lumen per square centimetre (equivalent to 10,000 lux).
| 1917 Trans. Illuminating Engin. Soc. (U.S.) XII. 440 Using the centimeter as the unit of length, the unit of illumination is one lumen per square centimeter, for which Blondel has proposed the name ‘phot’. One millilumen per square centimeter (milliphot) is more useful as a practical unit. 1939 [see metre-candle s.v. metre n.2 b]. 1953 Amos & Birkinshaw Television Engin. I. 280 The phot is rather a large unit, and its submultiple the milliphot (equal to 10-3 phot) is frequently used. |