This is an experiment. I have been trying the OM mount 75-260 zoom on my Olympus EM1 mark ii micro 4/3 camera, using an OM to M4/3 adaptor. This image was taken with the lens at 260mm, so with the quirks of the M4/3 system this becomes equivalent to about 520mm. And it is manual focus, so relying on my eyesight to ensure a sharp image.