Are there any reasons against buying a Sigma lens instead of a original Canon lens?

[darthdeus]

After considering to buy a Canon 24-105mm f/4L lens I realized that instead of upgrading to fullframe, I'm probably going to upgrade to 60D instead. That made me consider other options for a general purpose lens.

I stumbled upon Sigma 17-70 mm f/2.8-4.0 DC Macro HSM OS and found a lot of good words about it. I asked in local photography store and they said that it has much better optical quality than original Canon lenses in the same price range, like the EF-S 17-85 mm f/4-5.6 USM IS.

For a moment I thought about buying a 17-40mm f/4 L USM, but looking at some tests, it looks like the Sigma 17-70mm performs very similarly. I know that all Canon L lenses have superior build quality, but I don't really shoot in extreme conditions.

I know that there are multiple factors to consider, not only the optical quality, but considering that the Sigma lens is about half the price of the EF-S 17-55 mm f/2.8 IS USM, is there really that much of a difference?

I keep on searching, but I can't find any hard evidence against it.

[Elmo]

My primary lens for reduced sensor is a Tammy 17-50 f:2.8, Its a great lens. So is cannon always better for IQ? NO.

[inkista]

Sigma/Tamron/Tokina all make good lenses that are well worth their purchase price. The only drawback in going with a third-party is that they are not privy to Canon's design of the mount system. They're reverse-engineering the electronic communication signals that are used between the body and the lens. While a new 3rd-party lens will usually work just fine with the current version of the EOS mount, if Canon adds some feature, they'll only make sure their own lenses still work with the new signalling. They don't care if 3rd-party lenses do.

And depending on the age of the lens if Canon makes this purported change in future, Sigma may or may not rechip the lens for free. Or at all. Then again, it could be decades before Canon makes that kind of change. You pays your money and you takes your chances (and it didn't help the old FD/FL shooters back in the day to have Canon lenses when Canon switched to EOS; it's all a gamble).

One example of this future-compatibility issue is when Canon added the digital EXIF information to the body/lens communication in going from film to digital, a number of old film-body Sigma lenses lost their autofocus capability and needed to be rechipped. So, your main issue is going to be one of future compatibility. And how much you trust Sigma's service vs. Canon's service for their lenses.

In terms of image quality, it's often in the eye of the beholder as to what one is willing to pay for or isn't. For many folks, Sigma lenses are just as good or better. In this particular case, many say the Sigma is actually better than the 17-85.

But then a lot of folks have criticized the 17-85, which is probably why Canon came out with the EF-S 15-85 f/3.5-5.6 IS USM to replace it.

The one main thing to remember when asking about a Sigma lens is that you can't actually extend from one Sigma lens to all other Sigma lenses. Because the Sigma 17-70 has a reputation of besting the 17-85 doesn't mean all Sigma lenses are going to best all Canons. It really depends on the individual case. See this side-by-side of the 15-85, 17-85, and Sigma 18-125.

[PrimeTime]

Originally Posted by darthdeus

After considering to buy a Canon 24-105mm f/4L lens I realized that instead of upgrading to fullframe, I'm probably going to upgrade to 60D instead. That made me consider other options for a general purpose lens.

I stumbled upon Sigma 17-70 mm f/2.8-4.0 DC Macro HSM OS and found a lot of good words about it. I asked in local photography store and they said that it has much better optical quality than original Canon lenses in the same price range, like the EF-S 17-85 mm f/4-5.6 USM IS.

For a moment I thought about buying a 17-40mm f/4 L USM, but looking at some tests, it looks like the Sigma 17-70mm performs very similarly. I know that all Canon L lenses have superior build quality, but I don't really shoot in extreme conditions.

I know that there are multiple factors to consider, not only the optical quality, but considering that the Sigma lens is about half the price of the EF-S 17-55 mm f/2.8 IS USM, is there really that much of a difference?

I keep on searching, but I can't find any hard evidence against it.

You can review just about any lens at Camera lens tests, user reviews, camera accessory reviews - SLRgear.com! They give great reviews on alot of lenses. After looking at the 2 lenses you are considering, the 17-70 is very similar at f/4, but the 17-40 is much better from f/5.6 on. I would be willing to bet the canon L lens has better color and contrast as well.


If you look at the blur index charts at slrgear, you will see the sigma lens is somewhat soft in the corners.

[OsmosisStudios]

Originally Posted by darthdeus

I stumbled upon Sigma 17-70 mm f/2.8-4.0 DC Macro HSM OS and found a lot of good words about it. I asked in local photography store and they said that it has much better optical quality than original Canon lenses in the same price range, like the EF-S 17-85 mm f/4-5.6 USM IS.

Terrible sales staff: they shouldnt be pushing the 17-85 but the 17-55 f/2.8, which is likely better.