I was pretty excited to see Miles Hecker's comparison of the 1DsMkIII, 5DMkII, 5D, and 50D. I thought, finally someone will compare these cameras on a level playing field. I was a little bit disappointed in one aspect.
But first, let me say that for most applications, Miles' conclusions look sound. The 1DsMkIII and 5dMkII are the current kings of the canon lineup. No doubt about it, by comparison the 50d is second class; very good, but clearly second class when compared to the full-frame cameras.
What has me disappointed is this statement:
The 50D was moved further from the stage to compensate for the 1.0 vs 1.6 crop factors.
While this is a valid methodology for most applications, if you are trying to get long reach out of your camera/lens like a birder might, by moving back the sensor, Miles has handicapped the cropped sensor camera.
Try this on for size: The full-frame has always been the benchmark for lens and image quality because that is what we have had for decades. With the advent of the cropped sensor we started referring to lenses with "35mm equivalent" focal lengths. What if we turned that around and considered the system from the point of view of the cropped sensor.
In that case, we should have a test where we don't move either camera. We would simply accept that they have a different field of view. Depending on your application, this may be an advantage or disadvantage. I shoot panormaic/mosaic images, so the extra reach in the lens just means I stitch more images together. In that case, I have speculated that the 50D would come closer to the same resolving power as its big brothers because of the benefit of the crop factor.
I am suggesting that we shouldn't handicap this in all the tests. We should evaluate it as part of the system.
No doubt, the full-frame cameras are superior for most applications, but I am surprised that everyone is so willing to handicap the X0D series in analyzing these factors.
P.S. Many of you will probably recognize this as an extension of a rant I started a few weeks ago on the same topic. I recognize that I am fixated, but I am hoping to understand this issue more completely and this community tends to be a good one for ferreting out interesting methods of analysis.