As we are talking lenes used for aircraft photography ie telephoto's fall off is not an issue.
Wide angles will be but i dont use a wide angle when taking aeroplane photo's.
I am not sure what 100-400 you are talking about?
Couldn't possibly be the Canon one as i have never seen fall off at 1.6 or on a 1.3 body and i have only shot off around 50000 frames with mine?
Love to see an examply of fall off with the 100-400 on a 1.6 or 1.3 if you have one as i'd imagine every 100-400 user would dispute your claim to the highest level.
This shot has 10 pixels off the edge and 21 off the top and taken at a full 400mm.Please feel free to point out the fall off in the shot.
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Photo © Darren Howie
Quite surprised to see a dedicated Nikon pro rate the D2X so highly as well
You are totally correct about edges not being as sharp with lens sharpness.
However by the time you resize your 4000+ pixel shot down to 1280 or 1024 it will be that sharp that it will be irrelevant for aviation use.
Having used a 1DsMK2 with Canon's long primes(500+300)the quality you will get out of a 5D full frame will be unmatched except by its Nikon equivalent.