Practical guide to photographic & photo-mechanical printing (1887)
Burton, W. K. (William Kinnimond) · London, Marion and co. · leaf 462
A dvertisements 86 … By means of the Actinometer, the Actinic power of the light can be measured. It is based on the principle that a Phosphorescent Mineral, being exposed to light, acquires luminosity — the intensity of which is in direct proportion to the Actinic intensity of the existing light. The result is known…
Photography · Photomechanical processes
Internet Archive · Getty Research Institute · Public domain (published before 1931). Free to use for anything.
