Originally posted by stevebrot Where did you get that number?
The image circle for the A 50/1.7 is more than adequate for 35mm film and should not vignette on APS-C. At least mine doesn't.
Steve
Yes, 50/1.7, that's correct, and works fine because the diaphram is at the point where the rays cross over as they usually are so the width is actually small. (You're quite right btw glasbak, I just measured it, it's actually ~22mm @ 1.7) But the systems I use use an infinite tube to focus light in parallel onto the sensor, so it's a different gig. I've done a diagram to explain it better. Normally the iris is at point A so the cone of light rays is small and a diaphram opening of diameter
d suffices. In my case the iris is at point B so the same diaphram of diameter
d isn't big enough because as you can see the infinite rays are bigger than the opening. That's my problem. Err one of them
Last edited by Nass; 03-13-2013 at 03:16 PM.