The resolution of the 50D is 4752x3168. Assume that you are photographing object that fills the 1.6 sensor, so you get the full 15mp for the object.


The 5DmII has an actual resolution of 5616×3744. The portion of the frame that is cropped is determined by dividing the horizontal and vertical resolution by 1.6, giving us 3510x2340 -- a smaller value than the cropped sensor.


Thus, the object will cover more pixels of the 50D