However, you should note that stepping down to reduce light fall off on a full frame camera in the 5D case above is completely different from comparing the use of a DX lens on a film camera.
Light fall off of a 24-70 or 24-105 on a full frame camera is just light fall off, and can be reduced by stopping down. Light fall off is not even normally noticeable in everyday shots unless u are shooting scenes with a big blue sky within it, or shooting a huge white blank wall for example.
If you choose to use the 17-55DX on a Nikon film camera, what you have is not light fall off, but black borders around the frame between 17mm-24mm. No amount of stopping down will remove that, so once again, this is not even an apples to apples comparison.
Also, to better explain the "40% light loss" you mentioned, here's a quote from the same page in dpreview for the 5D review.
"...falloff of -30% would mean that if the luminance center of the frame was at exactly 100% (pure white) the average luminance of the corners would be 70%. Anything more than -20% may well be visible in everyday shots, although this depends on the framing of the shot and the exposure. "
Note that a fall off of xx% just means that the average luminance at the corners is 100-xx%. The 40% light falloff does not mean that the sensor receives 40% less light from the lens wide open.
So, if you guys really wanna compare the Canon and Nikon 17-55mm F2.8 for their merits/faults, you should be comparing them on the 1.5/1.6 crop factor cameras, where they were originally designed to be used on.
I highly doubt that you will be able to find any official recommendation/word from Nikon that even says or encourage you to use any DX lens with the film cameras.
Watcher said:
The same can be said on the 24-105L lens (in the other Canon thread) where this is vignetting and someone said that by stepping down, it will be reduced. The same reason was used when 24-70/2.8L on the 5D showed 40% light loss (measured by Canon pro Phil Askey) on 5D and yet was told "just step down".
What is good for the goose is good for the gander