AL> M is easier to use with manual focus because it has only one ring and AL> a good grip, but if F is substancially better optically, I'll go for
I do not think that the F is substantially better. I once tried out the 80-200 (or which it was - there were several from K to M) and it was pretty good. Also, it will be better suited for Mongolia than some part-plastic F zoom (I have seen them broken). Best regards, Frantisek Vlcek
