5D and Zoom Lens Vignetting Issues

Has anyone with both a 5D and zoom lenses noticed a severe amount of vignetting when shooting at the long end of the len? If so, is there a reason for this? I mean I can understand vignetting on my 16-35mm wide angle lense as the lense is actually wider than the full frame sensor... but at 100 .. or even 400mm? I shoot RAW so I am able to fix it to some degree in CameraRaw, but its a pain. I've included a sample below which I shot with a Canon 100-400mm L series lens (brought down the curves a bit to accentuate the vignetting). I am wondering if this is a 5D issue or a Full Frame issue. Any help in understanding this would be appreciated. Thanks.

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Stephen - as far as I can tell, vignetting is simply a fact of life with many lenses.

The problem can be easily and effectively dealt with using the PT Lens plugin. You may download it here:
http://epaperpress.com​/ptlens/

I've found it to be extremely useful for my 5D photography; the utility also works to rectify image distortion. Try it out and see what you think.

Thanks much for the info... so you would say its a lens issue rather than a full-frame issue then. I have used the same lens on a 20D with great results.. im thinking now it might have had something to do with the 1.6 crop factor... but I'll do some diggin' around.

Thanks for the software link... I am able to get it looking fine in PSCS2 but I like the distortion reduction in PTLens so I'll give that a try.

Cheers,

Steve

Certainly it's lens-related, and the full frame format utilizes the entire available area of focused light transmitted by the lens, so it's reasonable to expect that the effect would not be as noticeable on the cropped image of a 1.6 crop factor imager.

I think you'll like the PT Lens utility - it's practically effortless to use, and results are great. The linked image started out with substantial vignetting and I cleaned it up with PT Lens; results speak for themselves:

http://www.pbase.com/j​ohnme23/image/60621616

I haven't run into much light fall-off with my 100-400 except wide open at 400mm.