Just curious why the image circle of the Rodenstock Apo Sironar 360 N specs out to just 435 mm compared to over 494 for the Nikkor, 491 for the Apo Symmar and 485 for the Fujinon. Since these are all plasmats in Copal 3 shutters (maybe this is my problem! maybe they're not?), what has Rodenstock done (or not done) to produce this result? I suspect vignetting from the rear barrel? Then why not flare it? This seems a bit anomolous. Interestingly the image circle is 425 for its 300mm focal length and 500 for its 480mm focal length, more as expected and in line with the progression other manufacturers exhibit. So, who can please explain what happened at 360?
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