Originally posted by Clicker It's the character of the lenses wide open i believe...not all are affected that way except for the Voit which she already mentioned. Also most of the images seem to be taken from deep shade to a point of bright light so the "appearance" of vignetting is there.
Actually, just to be clear, since I am doing the Adobe lens profile calibration for them right now, so far almost all the lenses exhibit some vignetting wide open. The CV 15mm is the worst of all, but that lens has been known to have issues even on Leica M8, M9 etc. But even the Summicron 50 and 90 will have some vignetting if I shoot a white wall for instance.
I am however surprised by people who claim they see vignetting even on photos that are cropped and rotated.
The Summicron 35 photos are a little different. Because of the ND filter, some (maybe even most) of them have exaggerated contrast towards the centre, and contrast fall off towards the edges. I can understand why some perhaps less experienced eyes may perceive this as vignetting, but technically that's not true as there is no luminosity fall off.
However, even that wouldn't explain why someone would perceive vignetting on the first post, where there is no ND filter. Apart from monitor issues and eye perception issues, the only other reason I can think of would be expectations bias.