Hmm, I've not noticed this problem even when I was messing about at ISO 12600.
By no means is it a perfect image but at that high ISO for snapshots I was happy. Unless of course Lightroom auto-corrects for it and I just never noticed.
RedFox88: This is essentially a 24mm f/3.2 lens in terms of FOV and depth of field. Goes to show you can have really fast & shallow DOF glass on 4/3 like a 24mm f/1.4 camera for 35mm SLRs.
In terms of exposure, crop factor does not affect aperture but it's effective DOF is simply because the image is cropped.
Ohh, might finally be able to replace my 14mm 2.5.