Originally posted by Cabessius I have two CZJ Pancolar 50mm f/1.8 of different generations.
Just noticed that when I set them at the same aperture, the holes left for light gathering are quite different, being bigger at the newer one.
Is there anything wrong or is this normal?
Originally posted by photoptimist That does not look right.
At f/22, it should be 50/22 = 2.3 mm.
Originally posted by StarTroop Is it possible that the front elements have a magnifying effect on the aperture blades when viewed from the front?
The aperture blades on the newer 'electric' lens on the left appear incorrect. The older version on the right looks correct around 2.3mm.
The newer lens had 6 elements in 5 groups while the older lens had 6 elements in 4 groups. Yes, the magnifying effect will distort the actual aperture size, but not to this degree because of 5 groups vs. 4 groups.
Pretty sure your tests will reveal about a +2 EV over exposure with the lens on the left with shots in the f/4-f/22 range.