Looking for a general purpose walkaround lens
Comparing the Canon 17-85mm f/4-5.6 v. Sigma 18-125 f/3.5-5.6
Tested with a Canon Digital Rebel XT
Review by Ian Lind (www.iLind.net) April 2006
This is not a technical review, but a simple attempt to share my sense of these two lenses, both general purpose walkabout lenses affordable (in slightly different degrees) to the average amateur photographer.
Like many others, I returned to SLR photography about a year ago when I purchased a new Canon Digital Rebel XT. Money was an object, so I started with the kit lens. But the urge to upgrade was quick to surface and relentless.
My first attempt to replace the kit lens was the Sigma 18-125. I have been "reasonably happy" with the Sigma and it has produced some good images. Considering the price, it still seems like a good compromise. But I've noticed a few things. Distortion at wide angle and short distances can be substantial. Pictures of people at a reception, for example, leave some looking almost carnival mirror funny. At other times, I've felt certain photos were less than sharp, although it's usually easy to recover via Photoshop.
The only reasonable competitor in my view, based on specifications and price, is the Canon 17-85, a lens which has gotten decidedly mixed reviews from users on various photo sites. But I've had such a good experience with other Canon lenses that I wanted to give it a try.
So for several weeks I've been using a new Canon zoom and feeling quite good about it. It is quiet, fast focusing, and the IS has been a lifesaver several times. My very subjective feeling is that the Canon does a better overall job.
But when I used the two side by side over the past couple of days, I was surprised to find it difficult to find any meaningful differences in the resulting images.
The photos to the right were shot in RAW format, reduced in size, but without any other post processing. For all practical purposes, they appear identical. Obviously, they don't run the gamut of lighting conditions or colors, but at least suggest that there's no definitive winner between these two lenses in terms of overall image quality. Hit the sweet spot with exposure and focus, and either one will yield a quite respectable image.
The difference, then, will end up coming down to personal preference. I have a feeling, as yet unsupported by data, that the Canon yields slightly better or more consistent images, has a bit more margin for error, requires less correction, and has better contrast and color, although the differences are subtle and don't show up across the board.
But the Sigma 18-125 has a solid build, is smaller and several ounces ligher than the Canon, and can be purchased for 40% less. It also has a better macro mode.
After looking at the comparison photos, I think the Sigma deserves a very close look. I'm certainly going to try for more side-by-side comparisons before finally deciding which is the keeper.
Or I'll put it this way. Now that I've bought the Canon, I'll probably end up keeping it. But if I had borrowed these lenses, made this same comparison, and then had to decide whether to spend nearly twice as much for possibly real but marginal image improvement, it would have been harder to walk past the Sigma.