Canon 17-40 f/4L vs. Sigma 17-70 2.8/4.5

I just thought I would post a comment I received today, for those who care to know about the comparison.

"Hello there,

after purchasing the 17-40 L (my first L class lens) I ran some test (newspaper test and real life test) at various aperture (5.4, 7.1, 9.0) and focal length (17mm, 28mm, 40mm) between the 17-40 L and the 18-55 EF-S from the Rebel XT kit.

I was very disappointed by the 17-40. At 17mm the center sharpness was the same as the kit lens on the edges and the corners....the kit was better.

At 28mm and 40mm the 17-40 has an edge....except in the corner where the kit lens is as good or better.

The color is obviously better with the 17-40 and the contrast as well. However I found the 17-40 to have too much contrast to my taste. Contrast can be easily added in post processing...it is hard to remove without adding noise.

I was interested in this lens because it has the full frame compatibility. However after seeing the sharpness at the borders and corners on the APS-C format I clearly don't think it will be good in the corners of a FF sensor!!!!

So for a $700 lens I have to say that I was expecting better. I ended up like you...returning it to the store and taking the Sigma 17-70.

I ran the same tests...the sigma shows more consistency across the frame. The 17mm is the weak spot like the 17-40, however the sharpness from 22mm is better than the kit lens. All that for half the price of the 17-40. Only one remark, the color are a bit warm with the 17-70 where they were accurate with the 17-40.

Chromatic aberrations are virtually the same on the 17-40 and 17-70...way better than the kit lens.

I still consider the "L" class lenses from Canon. Beside the construction quality of the 17-40, I don't see why Canon put that lens in that class. Optical Quality is not there.

Regards,

Laurent"

I agree with the quality. These lenses weren't made for anything other than a full frame, and not a 1.6 crop! The 17-40 was nothing but a paper weight to me, and I got two NICE lenses for the same price as the 17-40. I guess if someone is happy with theirs, then that's all that really matters. Thanks for the info Laurent.