Archived posting to the Leica Users Group, 1999/06/14
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Slight correction. The 30, 50, 100 rule was based on a .025mm circle of confusion, which I believe is consistent with Zeiss usage. The Leica DOF scales appear to be based on a .03mm circle. To get the corresponding hyperfocal distances, use 26, 41, 83 instead of 30, 50, 100. (Not quite as neat.) The general formula is H = (F*F)/(f*c), where F is the focal length, f is the f-stop, and c is the diameter of the circle of confusion. This will give the hyperfocal distance H in millimeters. Move the decimal point three places to the left to get it in meters. Richard S.