Sigma 24-70 F2.8 DG DF vs. Tokina 28-80 F2.8 AT-X Pro Lens Test

Introduction. This page shows a comparison between the Sigma 24-70 and Tokina 28-80 "pro" lenses. These are the two latest generation pro lenses from Sigma and Tokina. Both offer constant F2.8 aperture and similar focal lengths. The Tokina is a little bigger, heavier and more expensive. I think it delivers superior optical performance as well.

For those that aren't satisfied with consumer level zoom lenses like the popular Canon 28-105 and Canon 28-135 IS, these lenses represent the next level of quality. If the Tokina and Sigma lenses don't satisfy, then the next logical choice is probably something like the Canon 28-70 "L" lens at more than twice the price of either of these two.

Methodology. All images were taken using a Canon D60 digital camera, mounted on a tripod, using mirror lockup and self timer to eliminate any camera shake. The target was a newspaper page, taped to a wall, illuminated by halogen lighting. The chart below shows cropped portions (from the center and edges) of several test images taken with the two lenses at three focal lengths common to each lens, and five different apertures.

Results. I encourage you to look at the images below for yourself, but here is how I interpret these images.

All things considered, the Tokina seems to be the better performer.
For "pro" lenses, I was surprised by how soft both lenses are at F2.8. Both lenses seemed to be softer wide open at the longer ends (70-80mm). With the possible exception of the Tokina at 28mm, I wouldn't want to use either lens at f2.8 (or F4).
In general, the Tokina produces sharp images at F5.6 and smaller apertures. The Sigma needs to be stopped down another stop or two to produce its best results. Even so, it never quite catches up to the Tokina in sharpness.
The Tokina seems to be better built, and switching from auto to manual focus is much simpler on the Tokina. The zoom ring on the Sigma that I tested was noticeably "stiff" between 50 and 70mm.

Conclusions. For me, image sharpness is important. Like the Canon consumer-level zoom lenses, I wouldn't want to use either of these lenses at their widest apertures. However, I would use these (preferably the Tokina) at F5.6. The Canon consumer zooms really need stopping down to F8 or F11 to produce decent sharpness.

Final Thoughts. I haven't tried a Canon L lens yet, but based on the reviews I've read, these two lenses seem to be about the "next best thing". Given this, two thoughts come to mind:

The Canon D60 (with it's relatively small CMOS sensor) places serious demands on the lens to deliver sharp images. While these lenses outperform the consumer zooms, they still don't bring out the best the camera has to offer.
Even a cheap prime lens like the Canon 50mm F1.8 can deliver sharper images than these "pro" level zooms.