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I'm looking for a new general purpose walk around lenses for my Canon XTI Rebel. Right now I have a the original Sigma 17-70 f/2.4-4.5 that does not have image stabilization, and looking to upgrade to a lens that does. I'd like to stick with a lens the can open up to a 2.8 aperture, and a wide focal length (15mm-20mm)

I've been reading a lot of reviews and have narrowed my choices down to the Canon EF-S 17-55 or the new Sigma 17-70 that has IS (or what sigma calls OS).

On B&H the 17-55 goes for $1099 and the 17-70 goes for $449. That's almost a 150% increase in price.

In comparison spec wise the 17-55 has a shorter zoom length, but also a constant 2.8 aperture and full time manual focus.

I've also been looking at the comparison shots on the-the-digital-picture.com, which seem to show that the 17-55 is a little sharper then the 17-70, but I'm really no expert at looking at these test shots, but they don't seem that different to me.

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=398&Camera=474&Sample=0&FLI=2&API=1&LensComp=713&CameraComp=474&SampleComp=0&FLIComp=2&APIComp=2

So what I'm trying to figure out is if the Canon is really worth the extra $650 over the Sigma? Both have image stabilization but is the Sigma version as good as the canon version? What about the Sigma USM auto focus? Is it as good as Canon's? The difference in focal length is not a big deal to me, but I would appreciate the constant 2.8 aperture and FTMF of the Canon although I'm not sure if that's worth and extra $650 to me.

Update

Here's a few graphs I generated by running ExposurePlot on my photos folder. As you can see most of my photos are wide angle, and wide aperture. Yet I also end up using a high ISO like 1600 a lot. I was hoping a lens with IS would allow me to handhold at slower shutter speeds and thus lower ISO.

From the answers so far it sounds like the Canon 17-55 might be worth the money over the Sigma. I've also been considering an L including the 24-70 and 24-105. But I honestly have no plans to upgrade to a full frame any time soon, nor require the build quality of an L.

Full Size

enter image description here

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    \$\begingroup\$ Sligthly false assumption there I think, Joanne. 1/70 is optistic; it works (more or less) well on full-frame at 70 mm but the crop has to be factored in. I'd call it 1/140 just to be safe. \$\endgroup\$
    – Staale S
    Commented Jan 30, 2011 at 2:11
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    \$\begingroup\$ A 70mm lens may still be a 70mm lens, but the crop factor does have to be taken into account when discussing blur from camera shake. A 44mm lens with a 1/3.5" sensor is going to be way more subject to camera shake than a 44mm lens on a 35mm sensor. \$\endgroup\$
    – Evan Krall
    Commented Jan 30, 2011 at 2:26
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    \$\begingroup\$ I tested one day and there's a huge difference in blur on my 50mm between 1/50th and 1/80th...even when trying to be steady, the 1/50th was at the edge of acceptable. I've switched to taking the crop factor into account for my steady calculations... \$\endgroup\$
    – rfusca
    Commented Jan 30, 2011 at 2:32
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    \$\begingroup\$ In any case, the question is still valid... Paying for IS under 100mm seems like a total waste of money to me unless you're seriously jittery. At those focal lengths it is a crutch for not using good form when shooting and the evidence I'll use for that is about 100 years of photography without image stabilization... \$\endgroup\$
    – Joanne C
    Commented Jan 30, 2011 at 2:35
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    \$\begingroup\$ These kinds of questions are impossible for us to answer. You are asking if something is worth the money, but we don't know how much you value your money or your lens. Some people fly economy class and others fly first class; no one choice is more "correct". \$\endgroup\$
    – rm999
    Commented Jan 30, 2011 at 5:12

3 Answers 3

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Forget the Sigma for using it wide-open. From experience, the maximum aperture is more a last-resort kind of thing there. Mine was extremely soft at 2.8, so I basically considered it an F/4.5-5.6 lens! Really, without stopping down by at least one stop, it wasn't pretty.

On the other hand, the Canon 17-55mm F/2.8 is really superb. Wide open it is good, and stopped down to F/4, it is extremely sharp.

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Not knowing anything about the Canon lens, I looked pretty hard at the Sigma lens when making my last purchase. I ultimately decided against it because several reviews said that 2.8 wide aperture quickly shrunk and was more marketing than useful, except at exactly 17mm.

If the wide aperture is important, I'd lean towards the Canon.

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  • \$\begingroup\$ Yes as you can see from my update above, wide aperture is important. Thanks for the suggestion .. even if it will probably cost me $600+ \$\endgroup\$
    – Eric
    Commented Jan 30, 2011 at 5:30
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I have the Canon 17-55. It replaced a Tamron 28-75. Even discounting the IS feature (which I find helps in low light), 28mm the Canon is better than the Tamron was across the board. If you get the 17-55 you won't regret the quality of the lens.

You might wish it were a bit longer on the long side, but I wanted a wide fast lens and it sounds like you do too. That's an expensive place to be.

FYI: something else you might consider in this space are prime lenses (fixed focal length). My favorite prime lens is a Sigma 30 f/1.4 (the Canon 28 f/1.8 is also very competitive). They are good lenses, a bit different for walking around, but lots of folks like them and use them for the walk around lenses.

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