The COC factor used to produce lens DOF scales varies between manufacturers within the same format.
For instance Carl Zeiss Contax SLR lenses have a far more generous DOF scale Pentax 35mm lenses. However there is no difference in the apparent DOF in prints made at the same aperture and FL using Pentax of Contax lenses. DOF scales, as opposed to actual DOF, add the variable of what size image you are viewing. So if one manufacturer uses a 4x5 print and another a 5x7 their DOF scales will be different but the actual DOF of the same focal length lens will be the same. Most DOF scales are optimistic IMHO. I usually will use the scale 1 stop open from my actual shooting aperture when utilizing hyperfocal distance. Butch Each man had only one genuine vocation - to find the way to himself. Hermann Hess (Demian)
