I had both of these at the same time for a couple of months and ran cursory tests of both. At f8 they are both much the same. At f 5.6 the 6x7 version drops noticeably in resolution and wide open at f4 the resolution is 50% (subjectively) of the 645 version. In comparison to itself, the 645 version only seems to lose about 10% sharpness wide open. It is a remarkable lens that, wide open, is sharp and contrasty corner to corner with no vignetting. At the prices you can get the 300/4 ED for now, there is no question as to which of the two you should get. (I assume you are not talking about the 6x7 300/4 ED lens, which I have heard is a very good lens but have no personal experience with.)
Warren -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
