Archived posting to the Leica Users Group, 1999/09/26
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]18% reflectance gray happens to be, from observation, the average middle tone in a grayscale scene according to what your eyes register. 50% reflectance gray images much lighter to your eye than 18% reflectance. This is because human perception of illumination and grayscale is non-linear. Godfrey >I'd like to know why the reference is 18% gray, rather than, say, >50% gray, which seems more logical. > >And how is 18% gray defined? Does this mean a random pattern of >18 black dots for every 82 white dots, or what? Most of the gray >cards I see look as though they are actually more than 18% gray, >but I'm not sure what the formal definition of this is.