200mm F2.8 L

Is there much difference between the mki version and the mkii.

optically, no

mki has a built-in hood; mkii has a detachable hood

Edit: got beaten to it : )

Many thanks for your help!!

As sol95 pointed out, the Mk I version has a built-in lens hood , but apart from that they are optically the same (superb!)

I once read that the construction is different. Number of aperture blades was changed and probably some bokeh difference. Or am I thinking about the difference 'tween the 2 versions of the 100 macro?

If you are planning to buy just go for the Mk II they are cheap second hand anyways.