View Full Version : Converting a Sironar-N?

Jim Rice
19-Mar-2007, 15:48
I tried just the rear cell on my 360 Caltar II-N and it formed an image that didn't look too sucky. I realize that I will lose a LOT of correction doing this and said lens is far from optimized for this stuff, but how bad would it be on film, really? Also, may I assume a 1.7 factor in focal length and f-number? Thanks, Jim

John O'Connell
20-Mar-2007, 14:05
I only ever did this with a 150 Sironar. Everyone has different standards, but I didn't do it again; low contrast, rather than sharpness, was the killer. I just guessed at 1.8 for the factor, but if you calculate the reproduction ratio you should be able to get ac accurate focal length with the Stroebel VCT formulas.

Carsten Wolff
28-Mar-2007, 21:47
Interesting. My "convertible" 240mm Sironar needs the rear group removed to work at the long end....(700mm in that case)...