Handbook of the practice and art of photography (1875)
Vogel, Hermann Wilhelm, 1834-1898, Molling, Edward F · Philadelphia, Benerman & Wilson · leaf 39
33 DISTRIBUTION OF LIGHT IN THE STUDIO. illuminated by the cone 6, a, c, which is considerably smaller. Still more pointed appears the cone which illuminates the point e, and thus, it is explained why a will appear brighter than a', and a' brighter Fig. 11. … a > than e. The opening of the cones of rays, or the angle which is formed by drawing lines from the point in question towards the window, gives us a criterion of its relative brightness. I call this angle the angle of light. When we take a point on the wall containing the window, the angle will be…
Photography
Internet Archive · Getty Research Institute · Public domain (published before 1931). Free to use for anything.
