This summer I was in the exact same boat, I compared the Tamron and Sigma(24-70).I actually borrowed fairly new copies of both lenses and did my own "controlled tests".
Sigma= I really wanted to pick this lens, it really is built to L lens standards. It was just not as sharp wide open when compared to the Tamron, it also seems to hunt for focus more(at all apertures) and sometimes would just be OFF by a little. When it was right on it was as sharp as any L lens I have seen but when wide open it was just not as sharp as the tamron.
Tamron= After handling the Sigma I was sure that I would not like this lens, it felt like a consumer lens. But I never noticed it hunt for focus under same conditions where the Sigma did, it is also quieter. And this one is actually VERY usable wide open, and is also very sharp throughout the aperture range.
To me it came down to being able to use F/2.8 confidently, yes I would have preferred to get a lens that was built like a tank but the build of the Tamron is actually better than most lenses in this price range($340).
... really bugs me to have a soft lens, drives me crazy like. so has anyone compared any of the mentioned lenses to a nikon or canon l type lens...just wondering how much of a difference in sharpness, build quality i would expect to be less and really don't mind that for the price
Jann I did not compare to the Canon lenses, but that was on purpose. If I had I am sure that i would not like the Tamron as much as I do. Kinda like test Driving a BENZ and then buying a Camry. Both good cars just not in the same class. So I test drove the ACCORD AND CAMRY, I just felt it was more apples to apples.
As for the Tamron I feel that it is very sharp and decently fast, but Build quality is not great. It is kinda like a heavy plasticy build, maybe even a bit below that of you 28-135IS. But no it is not a flimsy lens, like those cheap consumer level lenses or most kit lenses.
The build quality seems to be a key point as many people have had issues with the sigma AF sticking with use. Also, I've noted the tamron has a factory 6 year warrenty which is a great selling point.
Josh when my Tamron was a few weeks old I had a 20D setup with the lens on a TRIPOD and my wife decided to see what the quik release on the head was for... YUP down goes the camera onto the hard wood floor landing straight with the lens taking all of the force.
TAMRON did not need to fix the lens because it was not a DEFECT, it was abuse. but when I went to their local authorized service center, the man told me that since it was so new that Tamron authorized him to do the repairs under warranty. I was impressed and all I paid was a $54 fee to get a rush on the repair(was leaving town) and the lens was ready in a day or two.
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..i know oblio has said in the past the sigma pro line( don't remember the exact name) is good...i'm in the same boat as you nikonians...no money but would like a faster zoom. i'm happy with the range on my 28-135 IS( and the sharpness in general )but not the speed( 3.5-5.6) but then again hate to lose the range and if really bugs me to have a soft lens, drives me crazy like. so has anyone compared any of the mentioned lenses to a nikon or canon l type lens...just wondering how much of a difference in sharpness, build quality i would expect to be less and really don't mind that for the price
