They may be using different definitions of what is concidered to be sharp. Pentax uses a circle of confusion (CoC) being 0,035mm. If The Industar lens uses a larger CoC it may explain the difference. Otherwise it may not be exactly 50mm...
DagT > > Fra: "Boris Liberman" <[EMAIL PROTECTED]> > > Hello. > > Few days ago I received my own pancake lens. This is probably the > cheapest one - Industar 50-2 (50mm f/3.5) lens. I've been told that > being relatively slow and being based on classic Tessar formula, it > should be reasonably good optic... > > Anyway... I've compared the readings of DOF scale of this lens and my > M 50/2.0. Thankfully, it has proper DOF scale unlike modern FA 50/1.7 > that I also have. Industar has considerably bigger (right term?) DOF > for the same aperture. I cannot give the exact numbers, as I am in my > office. > > Nonetheless, I am confused - how can that be? I've been told that if > the lens has less elements (Industar is 4 lenses in 3 groups, if I am > not mistaken), then it presumably should have a bigger DOF. > > Please help me out on this one. > > Confused in Tel Aviv. > > Boris > >
