- If 'normal' is the diagonal of the frame, then 43mm is the 'normal' for 135 (24x36)format -- but 50mm is the one usually sold for 135 format cameras, but anywhere from 40mm - 58mm have been found as standard lenses for the format.
- If 'normal' is the diagonal of the frame, then 70mm should be the 'normal' for 645 (43x55) format -- but 75mm is the one sold for 645 format cameras.
- If 'normal' is the diagonal of the frame, then 148mm is the 'normal' for 4x5 (92x117 to 93x118mm) format -- and 150mm is one most sold for 4x5 format cameras, although some photographers have preferred as long as 210mm.
Note that the last two formats have ratio of FL:[short dimension of frame] of about 1.7x ...which would yield 40mm as normal, based upon that criteria, for 135 format.
Last edited by wiltw; 02-10-2011 at 04:35 PM. Click to view previous post history.