Originally posted by Pentaxor sorry, but that ain't possible. you need a lot of room for processing power and a pretty big lens inorder to have that kind of IQ.
Actually, K-7 and 645D have identical electronics. Identical down to the two main processors, buffer memory, 4 channel read-out DACs, HDMI and 921k LCD drivers. The K-7 has additional electronics for audio, the 645D for 2nd SD card.
Originally posted by Erik I don't feel like doing the math at the moment but f/2.8 in medium format gives much shallower DoF than f/2.8 in a 35mm or APS-C lens.
Originally posted by ogl DoF of f2.8 at 645 = f1.7 at 35 mm.
DFA 645 55/2.8 and Sigma 30/1.4 render about the same images (both using a cropped sensor). The DFA 645 is much lighter and about same size.
However, this entire consideration misses the entire point.
A 645D is built to turn studio light or daylight into upmost resolution and dynamic range.
Where an f/2.8 lens may still deliver 80 lp/mm, it will be hopeless for an f/1.4 lens to deliver the required 160 lp/mm to compete.
And the sensor will be too small to have a large enough potential well to store all those electrons for high dynamic range.
Therefore, the usual APS-C vs. FF "argument dynamics" doesn't apply to MF. Because light simply is at ample supply.
BTW, in this situation, the K-7 is a much better camera than K-x. May be a point of interest in this K-5 discussion