As to considering changing over to a Pentax 645: I recently bought one with standard lens and I can only agree that the lens is a marvel of sharpness. Moreover the "bokeh" , the transition from sharp to unsharp is also great. Unlike many of its competitors the Pentax offers a lot or rather is all singing and dancing: comes with autofocus, programmes, built-in winder etc. at a price the others can only offer basic cameras (with viewfinders etc all at extrta cost)