I am thinking of purchasing a P21 + for my Contax 645........my only concern is the 1.3 crop factor. Has anyone found it a pain in the ass? I shoot alot at F2.8-5.6 so I like the look I get with shallow depth of field and would hate to have to compromise any of the lens qualities. i shoot with a canon 1ds right now but dont like it. any feedback appreciated. my only other option right now is a P25 back but cant afford it. thanks in advance for feedback.