To me, it certainly seems like the 20D is pushing the boundaries of usefulness for the 100-400 already.
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Jani,
Such reckless and extravagant statements need nipping in the bud.
It's true there's a 'law of diminishing returns' at work here. For each proportional increase in sensor resolving power one cannot expect an equal and proportional increase in 'system' resolving power without also an increase in the resolving power of the lens used. This of course does not generally happen. Canon keeps releasing new camera bodies with greater resolving sensors but is apparently not able to provide new lenses with a similar degree of improved performance.
However, the evidence before my eyes does
not lead me to conclude that sensors have reached the stage where they can be said to have 'out-resolved' lenses. All you have to do is check out the MTF charts at photodo to see that all good lenses can out-resolve any sensor that's currently available, and sometimes by a big margin. Even the 100-400 IS zoom at 400mm and f8 would appear to at least equal the performance of the 20D. By that I mean, if the lens can deliver 50-60% MTF at 40 lp/mm (the photodo chart) then it can probably deliver 20-30% MTF at 60 lp/mm which is the resolution limit of the 20D.
Since some people have in the past accused me of being too theoretical and impractical, I'm going to put my money where my mouth is, or 'walk the talk' as the Yanks say. The following series of 300-400% crops (the 5D needed greater enlargement) might look like I discovered a new planet in the solar system. But in fact it's merely a piece of a used, medium grade, orbital sanding disc which I stuck on a piece of plywood.
I could show you some crops of a Norman Koren test chart indicating the superior resolving power of the 20D over the 5D (using the 100-400 zoom), but I know some of you are only interested in 'real world' results and have a great disdain for test charts.
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For those of you who might feel it necessary to question my procedures, or think maybe I didn't focus properly, I provide the following notes.
(1) The 100-400 lens was mounted on a sturdy tripod. I used a remote cord and MLU even though the shutter speed was mostly above any MLU concerns.
(2) I kept shutter speeds as close as possible for both cameras at the same f stop by varying ISO, and of course I did not use IS.
(3) Having focussed on the target to the best of my ability, I kept autofocus
off for all shots and used the same focussing for all shots. I did not remove the lens from the camera but the camera from the lens.
(4) The RAW images were converted in ACR with auto-settings off, and luminance smoothing and sharpening at zero. I later tweaked the images in 'levels' only, to get their general appearance similar.