Julius Wong 
, Oct 02, 2005; 03:04 a.m.
I have used this new lens for over two weeks on an EOS 20D with
satisfactory results. Yesterday I mount it on my new 5D and took a
test shot wide open (24mm at f/4). When I examined this picture on my
computer, not only were all four corners vignetted, the left and right
sides were darkened as well.
I am puzzled over such poor performance of this new US$1250 "L" lens
at the edges. I am wondering whether the old EF 24-70/f2.8L would fair
better.
I took a second shot at my floor tiles. This time not only were there
vignetting around the corners, but straight lines were converging like
my EF 15/f2.8 fish eye lens. Is this suppose to happen at 24mm? I am
considering returning this lens to Canon in exchange for the EF
24-70/f2.8L. Such performance on a full frame sensor is simply not
acceptable.
Notice the darkened left and right sides as well all 4 corners
Terry Smith , Oct 02, 2005; 04:11 a.m.
I posted test results for this lens on here about two weeks ago from the French photomag Chasseur d'Images. They said while the lens is exceptionally sharp at all apetures and focal lenghts, vignettage and distortion were majot issues, especially at the short end wide open. You got exactly what they found out on their high-tech test bench. Distortion is almost 1.5% barrel, what you'd expect from a kit lens and it shows up in your photo just like the dark corners show up. In this kind of situation, bump up the ISO and close down the lens by two or three stops each. Of course that won't help the distortion but at least the corners will be clean.
Cliff Shone , Oct 02, 2005; 04:21 a.m.
Hi Julius
Did you have the lens hood and any filters mounted? If so, is the vigenetting still as severe with them removed?
Julius Wong , Oct 02, 2005; 05:03 a.m.
Thanks Joe for the advice. No I have not read that French report. And Cliff, I did not use any filters nor any lens hoods. I double checked my result by shooting at floor tiles but the result was just as disappointing.
However, when I mounted my EF16-35/f2.8L to shoot at 16mm, the vignetting and distortion are similar. So I guess this is a typical Canon problem at the wide end which has escaped my attention due to the fact that I have been shooting primarily on the 10D/20D APS-C sized reduced frame. The edges of my "L" lenses were rarely used. Hence I had never noticed this problem.
I have heard in the past that Canon's wide angle lenses leave much to be desired. Now I know why. I should perhaps heed my friend's advice of buying the Contax 21mm lens instead.
vignetting and converging lines of the EF24-105/f4L IS at 24mm and f/4
Christian Hoffmann , Oct 02, 2005; 05:11 a.m.
Hmm, that's bad on such an expensive lens...
Julius Wong , Oct 02, 2005; 05:26 a.m.
I am attaching another shot of the same floor tiles for comparison.
Similar vignetting and converging lines distortion on the EF16-35/f2.8L lens at 16mm and f/2.8
Yakim Peled 
, Oct 02, 2005; 05:44 a.m.
Maybe Canon wishes to encourage people to use 1.6X and 1.3X bodies?
:-(
Happy shooting,
Yakim.
Julius Wong , Oct 02, 2005; 06:35 a.m.
I can hardly agree, Yakim. With the arrival of the EOS 5D, FF is Canon's advantage over all competition. As such I just cannot understand the vignetting problem I discovered by chance.
Since my couriosity has been aroused, I tried a couple of more EF lenses on my 5D. Sure enough the same vignetting of corners appeared on the EF50/f1.4 standard lens and the legendary EF135/f2L portrait lens.
My observation has been confirmed by a friend who owns the 1Ds2. Funny none of us noticed the vignetting problem on "L" lenses back in the dark ages of film. His explanation is that perhaps it has something to do with how digital sensors collect light. Thus the problem has become more pronounced after we switched to digital camera bodies.
Perhaps the great Bob Atkins has a more thorough scientific explanation.
Corner vignetting of the EF135/f2L portrait lens at f/2 as shown on the EOS 5D.
Roisin Murphy , Oct 02, 2005; 07:01 a.m.
and is this only the 5D sensor, or is it the same story with 1Ds and even tele lenses vignetting?
Johan Greenhorn , Oct 02, 2005; 07:02 a.m.
Most lenses vignette wide open. Perhaps it is just visible on 5D more beause people use more these new contrasty and saturated picture styles that amplify vignetting. Take 2 shots, one in "neutral" mode and another in "landscape" mode, and I'm sure "landscape" shows more vignetting. It is the same on film cameras with different films.
