[Brightcolours]

I do think f1.8 for 9mm makes sense for a MFT lens. Usually the sweet spot of a lens is reached after stopping down about 2 stops from the maximum aperture. If the maximum aperture is f1.8 then the sweet spot would be around f2.8-f4, just corresponding to f5.6-f8 for a FF lens. If the maximum aperture is f2.8 then the sweet spot would be around f5.6-f8 but then diffraction already comes in for MFT.

 

In fact I think all primes for MFT should start the aperture from at least f2.

There is no reason to assume an f2.8 lens on MFT would be not sharp at f2.8. No basis for that claim. A bit too simplistic an argument, I fear.