>>4179792Which is entirely correct if you're resolution limited by your lens.
Which, if you're shooting on 20mp MFT, you need an mtf50 of 162 lp\mm, or 83 lp\mm on 24mp full frame.
The $2600 canon 70-200 RF peaks at 83 lp\mm in the centre and 72 lp\mm in the corners. The figures I gave above are a minimum though, ideally you want just over double to account for the Nyquist limit of a digital measurement.
In reality, the only way to get longer reach, is to use a longer focal length.
Smaller sensors also have the problem of being diffraction limited much sooner, it's around f5.6 on full frame 24mp, but f2.8 on MFT! Which means for especially long focal length, full frame tends to be much more affordable and compact, as f5.6 is a much easier lens to make than f2.8!
