« on: April 25, 2013, 08:38:24 AM »
I have the 24-70mm II and the Sigma 35mm f/1.4. Both are great, but have to disagree that the 24-70 II is sharper at 35mm than the Sigma at 35mm. If you compare the IQ from both at f/2.8, the Sigma has an edge in center and mid frame sharpness. This comparison can be seen at the the-digital-picture.com:
And the Sigma is two full stops faster; makes a big difference in the bokeh department.
I saw the same crops before making my post but came to a different conclusion. I agree that the Sigma is slightly sharper in the center but saw the Canon slightly better mid frame (more vignetting but better contrast) and better in the corner. Lens to lens variation might flipflop the center and midrange results, but it looks like the Canon should retain its advantage at the corners.
In either case, the difference between the two is not big enough to pick the S35 over the 24-70 II unless you need a larger aperture. That was the part that surprised me -- how good the 24-70 II is. I'm not surprised that newer designs beat older designs but I am surprised that the new S35 prime does not beat the 24-70 II. I'm also impressed by the 24-70 II's AF speed/tracking ability in AI servo when I shot a young boys basketball game on a small court (standing at the baseline because there are no bleachers). It's like a mini 70-200. I know the 35L and 50L can't track like that (I haven't used the Sigma so I don't know about how that does in servo). Before, I used all primes to cover the midrange focal lengths because they were better than the zoom options at the time. Now, I use primes for low light/shallow DOF applications only, which means that I use them about 1/3 as much as I used to.