i have a bit of an academic question for the optics experts in the group. i was recently discussing using process lenses for infinity work with someone who is quite knowledgeable on such matters. we were going back and forth on the merits and limitations of the lenses, noting the usuals...

Pro: Lenses are small and usually very sharp at f/22 and beyond
Cons: Lenses are not designed for infinity use, and need to be stopped down a lot to get acceptable results at infinity

he then said something that i'd not heard or even thought about before... that process lenses, we were specifically talking about the APO-Ronar, which is, i believe, a dialyte, have shallower DOF at a given f-stop than lenses of other designs. i told him that Linos could adjust the spacing to optimize the APO-Ronar for distant shooting, but he said that would only enable one to shoot the lens with acceptable results at f-stops below f/22, it would not correct the narrow DOF inherit to the lens design.

he held that due to the lens design, an APO-Ronar that was modified for distant work, would still have less DOF at the same f-stop as a different design, say a plasmat or tessar.

is there any truth to this? does that mean that the fuji 300-c, which is essentially a dialyte optimized for infinity work, will have less DOF than a 300mm lens of another design at the same f-stop?

whether this amounts to any real difference in use is a separate argument altogether; i'm just wondering about the theory.