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Old Jan 8, 2011, 4:28 PM   #11
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Originally Posted by itsme000 View Post
So you're saying that the Sigma OS 18-50 F/2.8 isn't quite as good image quality wise as the Sigma 18-50 F/2.8 without OS that's half the cost?
Yes. See:

Canon EF-S 17-55mm f/2.8 IS USM (Tested)
Canon EF-S 17-55mm f/2.8 USM IS
Canon EF-S 17-55mm f/2.8 USM IS


Sigma AF 18-50mm f/2.8 EX DC Aspherical IF


Tamron 17-50mm f/2.8 XR Di II LD Aspherical IF SP AF (Tested)
Tamron AF 17-50mm f/2.8 SP XR Di II LD Aspherical [IF]


Tokina AF 16-50mm f/2.8 AT-X Pro DX


Sigma AF 17-50mm f/2.8 DC HSM EX OS


Tamron 17-50mm f/2.8 XR Di II VC LD Aspherical IF SP AF (Tested)
Tamron AF 17-50mm f/2.8 XR Di II LD Asph. [IF] VC
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Old Jan 8, 2011, 6:55 PM   #12
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I've checked them out both. I'm not sure what you're talking about.
Distortion on non-OS was tested at F/5.0, OS was tested at F/10.0
The distortion on OS at 17mm @ F/10.0 was -2.91%, non-OS 18mm @ F/5.0 was 2.13%

Vignetting on one was tested at 18mm, the other at 17mm. Perhaps this might account for the difference.

Resolution is substantially higher across the entire range and chromatic aberration is substantially lower across all range on the new OS version compared to the older 18mm on non-OS.

So, I'm not getting why you claim the non OS is better. What am I missing here?

Last edited by itsme000; Jan 8, 2011 at 7:16 PM.
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Old Jan 8, 2011, 10:10 PM   #13
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I posted all the test results for those lenses on Canon cameras. Unfortunately, you happened to zero in on the two reviews that were done on different camera bodies, one at 15MP and one at 8MP. You really can't compare the results across brands and bodies, so those results don't tell the whole story. I also erred by including the test results for the older Sigma 18-50/2.8 instead of the newer 18-50/2.8 Macro, which is better, but PhotoZone.de doesn't have test results for the newer lens on a Canon body.

In order to really make a good comparision, you need to see how the lens compares with another lens that was tested on both bodies (or brands) and see how that other lens compares with the lens you are interested in. That works, but it's convoluted. If you're interested, you can see what I mean by scanning the reports on http://www.photozone.de/reviews.

Sorry about the confusion.
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Old Jan 9, 2011, 8:16 AM   #14
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Exactly!!! (See note): http://www.photozone.de/Reviews/overview
"Please note that the tests results are not comparable across the different systems! This does also apply for the new EOS tests based on the EOS 50D because of differences in the sensor system (e.g. AA-filter) as well as different RAW-converters."

i.e. The same lens also tested better on one (Canon) body than the other:
Canon EF-S 17-55mm f/2.8 USM IS
Canon EF-S 17-55mm f/2.8 USM IS
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Old Jan 10, 2011, 9:43 PM   #15
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Agreed - I'm only referring to 3rd party lenses

By all mean get the USM if you can afford it (it's also quieter). The Tokina only stands out because it's an excellent lens (it's all metal, not so sure about the others), and as mentioned, it is probably 2nd in cost but indeed is the widest and optically it hangs up there with the best.

I now know. Sigma HSM, it's not real ring motor. When its put in AF, the gear is mechanically linked preventing you from hand-turning the ring at all (without damaging it), just like the kit lens "USM". It has a geared drive-train.


Anyways, so there is no objective comparison showing 17-50mm OS is inferior/superior to 18-50mm non OS that's no longer made considering there is no consistent testing, is there?
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