Originally posted by richard0170 And you should want to not use wide angle lenses designed for K or other SLR systems on mirrorless cameras as they are reverse telephoto lenses - to make space for the flipping of the mirror, and hence have worse IQ than real wide angle lenses which do no have to leave space for a mirror.
Depends on the mirrorless camera.
On the smaller sensors of the Q, what you call "real" wide angle lenses,
like an old Gauss-type Leica M Summicron 35/2 that I've been using recently, do very well.
But on bigger sensors, reverse telephoto lenses do better,
since they're sending the light rays straight down into the pixels,
and not angled in where they're likely to get cut off.
Even for normal lenses on (D)SLRs, reverse telephoto lenses like the newer Zeiss Otus
are giving better IQ than the older Gauss-derived lenses like the Zeiss Planar.