My trusty old Sigma 24-70/2.8 has little wrong with it than a noisy slightly slowish focus and some noticeable radial distortion in the corners at 24mm. But the corners finally interfered with a shoot the other day and I decided it was time to upgrade. I ordered the 24-70/2.8 HSM from B&H ... waited 2 days ....

First out of the box it appeared that it was worse than my old 24-70/2.8. More flare prone, softer. So, because I really needed an upgrade (90% of the indoor photos of models I take are with a 24-70/2.8, and it's an important lens to me), I picked up a new 24-70/2.8L at Keeble and Shuchat on the way to work.

Time for a bakeoff.

The results were, initially, not definitive. After studying a number of photographs of some our bookshelves I decided that the Sigma lens is slightly sharper and contrastier. Sometimes the Canon was the better of the two but the Sigma was the better of the two more often.

The corners now looked just fine to me. I'm not sure what that was all about. Something must have gone horribly wrong with my "just out of the box" test protocol that morning.

The other major visible difference is the bokeh. The Sigma lens produces bokeh with a defined edge. This sometimes produces nervous or double ("nisen") out of focus areas, which are sometimes distracting. The Canon, on the other hand, produces bokeh with soft edges. That's not ideal either, but it blends together better in the background. After taking a whole bunch of photos with both lenses I did come up with one or two where I thought the effect of the Sigma's bokeh was unacceptable. It was sort of a contrived situation though.

Anyway based on that I decided I'd be keeping the Canon and returning the Sigma, but I took both of them with me for this weekend's shoots, figuring I'd compare them some more.

A little later I started shooting my model with the Canon 24-70/2.8L. Annnnnnnnnd ... at 24mm the lens front focused. By several inches. It was just fine at 70mm.

So I wrapped up the Canon, switched over to the Sigma and took about 1200 photos.

Both lenses: Excellent sharpness, acceptable CA, fast focus, silent, excellent build
Canon pros: Better if imperfect bokeh, excellent CA correction, sort of weather sealed
Sigma pros: A little smaller, lighter. Focuses correctly. Every time.

So now the Canon's going back.