辐透

辐透（英文phot，符号ph）是光度学所用的照度单位，也就是单位面积内通过的光通量。

辐透并不是国际单位制的标准单位，而是旧式CGS单位制的单位。名词phot是André Blondel在1921年创造的^[1]。

在公制单位中：

1\ \mathrm {phot} =1\ {\frac {\mathrm {lumen} }{\mathrm {centimeter} ^{2}}}=10,000\ {\frac {\mathrm {lumens} }{\mathrm {meter} ^{2}}}=10,000\ \mathrm {lux} =10\ \mathrm {kilolux}

公制量纲：

照度 = 发光强度 × 立体角 / 长度²

另见

^ Parry Moon. "System of photometer concepts", in the Journal of the Optical Society of America, volume 32, number 6 (June 1942). – Page 355: "The lumen was proposed by Blondel in 1894 and is now universally accepted. The names, phot and stilb were likewise coined by Blondel (1921) and are in general use on the Continent."