Originally posted by rob1234 How do you find the M20/4 on FF digital? My copy never gets sharp in the extreme corners on film, and looking forward to trying it on the new Pentax FF.
I see the same on the A7.
In fact I think I have some impression and views on this in an earlier post here.
Don't know if it's the sensor stack thickness of the A7 or inherent in the lens.
Since you get it on film too, maybe it's a lens thing.
That said, I do find that at f11, its passable, and its really only the corners and the sides are good.
Less field curvature problems too vs many f2.8 20mm lenses.
In fact many faster 20mm have more issues with sharpness just past the center of frame. (On A7 at least)
Also in my own practical use, its often cropped off once I fix for distortion or choose a non 6x4 aspect ratio.
I've also printed A4 and the corners were not apparent at all.
The size/portability, balances off well against only the last bits of the corner IQ for me.
Btw, my A7 has been sent for a thin filter mod, so I will be certain how much the sensor stack affects these old SLR wides.