Originally posted by Samsungian But overall isn't the Leica body smaller than 645D?
Probably not. The 645N II is 147 x 109 x 117 mm and weighs 1280 g without batteries, the S2 is 160 x 120 x 80 mm and weighs 1410 g with battery.
So, if we assume the 645D is similar to the 645NII, what happens if you mount a lens?
If you mount the 75/2.8 on the Pentax and the 70/2.5 on the S2, the Pentax is suddenly much smaller in all respects: The depth grows to 154.5 and the weight grows a mere 215 g to 1495 g, while the S2 grows to a depth of 173 mm and a total weight of 2150 g! So you can add a wide Pentax zoom and have a flexible two lens kit and still stay below the weight of a single-lens kit S2 :-)