Distortion is cheap to fix in post. Field curvature, astigmatism, coma, and chromatic aberration need to be handled optically. A larger sensor remains benefici

Distortion is cheap to fix in post. Field curvature, astigmatism, coma, and chromatic aberration need to be handled optically. A larger sensor remains beneficial, even if the lens is physically larger, at least as long as you keep a wide aperture. There is a hard limit at F/0.5 that you won't get closer to than ~ F/0.65, but the crop factor makes it so you have a smaller absolute aperture with a smaller sensor to get the same field-of-view. MFT needs half the focal length and half the F-number to match full frame in FOV and DOF. E.g. an F/1.3 full-frame lens already matches what exotic optics can reach on MFT, and an F/1.0 one would match the theoretical limit of MFT. Speaking about more realistic MFT lenses like F/1.4, that'd be a rather harmless F/2.8 in full-frame. Yes, the latter is more expensive, but only because F/1.4 is quite a bit away from F/0.7, the practical limit for "normal" photography lenses (anything faster is probably exotic).