Canon 17-40L Corner Sharpness

I am looking for real world feedback regarding the corner sharpness of the Canon 17-40L. I have read several reviews stating that the lens is soft at the corners.

I have this lens, but I have only used it so far on a Canon 20D. I haven't noticed any problems; however, because of the smaller sensor I know that I am not seeing the extreme corners. I have just upgraded to a 5D which I just received yesterday. I would like some feedback on your real world experience with this lens on a full frame camera. I know that many superb photographers on this site use a combination of the 5D and the 17-40L and judging by the quality of your images it does not seem to be a problem.

I have been wondering if it might be a good idea to switch to a 24-70L now that I have a full frame camera if corner sharpness is a problem with this lens.

Thank you in advance for providing feedback.

I use the 17-40 on a 1DMK2 which is a 1.3 crop. It is not quite full frame, but I have not had an issue. I do believe you will notice some fall off on a 5D. I do notice I must be careful to point the camera up as little as possible to avoid the perspective distortion of narrowing at the top. However I believe this is true for any wide lens.

I would hesitate to go with the 24-70 as 24 just isn't wide enough for most photographers.

I did read an interesting article on using the Nikon 14-24 with an adapter for Canon. Manual focus and a funny way to set f stop, but lens looks super.

I have the 17-40 with the 5D and when I am shooting wide it is very noticeable and drives me crazy. I've now resorted to combining multiple images to avoid having to shoot really wide. This is one thing Nikon has going for it, they have some decent wide angle lenses.

Here is the link to the article I mentioned above http://www.davidclapp.co.uk/articles.php

And another earlier comparing the 17-40 directly
http://www.davidclapp.co.uk/nikon1424.php

Thanks for the feedback!!

The quality gets worse closer to 40mm. I heard the 17-40mm is sharper on it's wider end than the 16-35mm. I wonder if the 16-35mm is better w/ the edges? I don't think many people are really that anal about it. The sharpest zoom out right now is the Nikon 12-24mm but you can't get any filters on it. If you're really worried about it you should be using prime lenses. I started w/ primes but swithed to zooms as I went digital. I'm finding very hard to go back and all I have is the 24mm T/S.

Oops I meant nikkor 14-24mm, F/2.8

Have you read Darwin Wigget's article on this subject? He compares the Canon 16-35mm to the 17-40mm and describes his work around. With your 20D you won't notice the edge softness because the smaller sensor crops the soft edges.

http://www.naturephotographers.net/articles0508/dw0508-1.html

If the 24-70 can replace the 17-40 it means your not a superwide shooter and you should get a lens that better suits your style. The 24-105L IS has advanages, but the 24-70 seems to have somewhat better IQ in its range.

You had a standard zoom with the 17-40 on a crop camera. I feel that most people will want that on FF too.