i am considering a 50mm lens for a hasselblad 500cm. the CF version seems to be running about $800-900 on ebay, while you can pick up a C version for much cheaper, maybe $300-400. the C version looks a little funny with its flared out front end, but is there any opitcal reason why i would want to go with the CF version instead of the older C version? also, does the C version require the round, screw- in type lens hood? or do they both use a bay 60 square lens hood? thanks.