[Brightcolours]

Maybe what they are trying to say is: "It's equivalent to a 600mm w.r.t to FOV. DOF is very thin at this point and (most importantly) f/4 is good enough considering the ISO-capabilities of current m43 cameras."

And I think I agree with this Also, there is no 600mm f/8 lens to compare with as far as I know and the usual 600mm f/4 play in a different league (also in terms of price, size and weight) so this equivalence discussion is a bit pointless anyway isn't it?

You are correct in that there are no 600mm f8 lenses. This is one lens where MFT has a size/weight advantage, just because there is no 600mm f8 (let alone with IS).

 

However, lens equivalency is not about proving MFT is somehow bad/worse (it of course is not). It is just about understanding which lenses do what on which format. Nothing else. It probably will be a nice and attractive lens for MFT.

 

To get an equivalent lens on FF, one would have to get a 300mm f4 and add a 2x TC. Or a 400mm f5.6 lens with an 1.4x TC. The new Tamron 150-600mm will probably be a contender on FF, when closed down to f8.