9 out of 10 points and recommendedTack sharp, extended focal rangeFocusing a bit loud
I have this lens for a year, and meanwhile I got to make an informed opinion about it.reviewed April 3rd, 2008 (purchased for $600)
I've seen the other posts and I don't know what to make of them; regarding image quality, it's the best "normal zoom" lens. Extremely sharp even for macro photography, and even when using 25mm macro rings.
Sharpness: excelent, my copy is as sharp as Canon's 17-55IS and vastly superior to the Canon's 17-85IS; wide-open is amazing, and if it was made by Canon it'd get an L designation.
Chromatic aberation: extremely low, under one pixel even in corners.
Flare: very resistant, and the included lens shade makes short work of it.
Contrast, color: perfect. I used it for three weddings (coupled with a Canon 30D) and half of the time was used wide-open, for "available darkness" photography; the shadows held up with lots of detail, and colors were accurate indoor and outdoor.
A friend of mine aquired a good copy after turning down another two, but I got mine as the last one from the shelf (so I couldn't afford the luxury of hand-picking between copies); nevertheless, I ended up with a perfect one.
Regarding the batch variance, I don't know what to think; people seem to have various opinion, but a certain regard could not change: bokeh. Contrary to some other views, my Sigma produces butter-smooth background both wide-open and when stopped down to f/6.3-f/11; this is part of the design, and a requirement for portrait and macro.
The only gripe that I have is that the focus is loud; on the other hand, focusing is done quickly in all but the darkest environments.
Overall, I recommend it wholeheartedly; it's head and shoulders above any kit lens (18-70 Nikkor, 18-55IS), and it has a very useful focal range while being satisfactory luminous.
P.S.: the price was a bit high, but that's because in Europe everybody pays a price premium.
9 out of 10 points and recommendedBuild quality, luminousCA
I have this lens for more than a year, so I can give a balanced opinion. I mainly used it on a Canon 30D, 90% of the time set at a fixed 12mm, and I was in doubt if I should fork almost the double amount of money for the EF-S 10-22; while now I know that Tankina is a great lens, Canon 10-22 has a few tricks of its own.reviewed April 3rd, 2008 (purchased for $800)
The best part: Tokina 12-24 construction is very (and I mean VERY!) sturdy. The included lens shade is good, and the interior surface is satin-matte to avoid any reflection.
I use it mainly for "creative" angles, so the wide end gets me an accentuated perspective.
Compared to the Canon's 10-22, the weak point is distortion; even in a very flat plane the corners are significantly skewed, so you can't really use it for large groups of people. Also the 12mm end is not that wide; one can get significantly more from Canon's 10mm.
One other use is landscapes, and this is hands-down the best option; the contrast and colours are very pleasant, and it has something that really make the pictures look bright.
As a bonus, I used it on a film camera; from 15-18mm you get acceptable vigneting if you DON'T use the lens shade.
Last, I would like to mention that it's decent wide-open at f/4, but the best results come from f/6.3.
Overall, it's the best alternative non-manufacturer lens; I would advise against Sigma or other equivalents, and only if you have excess money you might think to buy the Canon 10-22.
LATER EDIT, after more than three years of (pleasurable) use:
It's an excellent lens, and its only drawback could be the somehow antiquated technology; Tokina seems reluctant about newer autofocus engines, and also the chromatic aberration could be a bit lower.
In its defense, here's the lowdown:
1) Image quality: very decent at f/4, with only some soft corners; but if you need speed, the Tankina delivers and I wouldn't hesitate using it indoors wide open. It's especially nice on close-ups for intentional deformation given by the wide-angle.
2) Geometric distortion: most of the time there isn't sesizable distortion, only the usual one produced by any wideangle. Usable even on people, if you take care to post-process it accordingly (lens deformation filter in Photoshop gives a straightaway rectilinear image, with no waviness).
3) Chromatic aberration: nothing to be worried about; it has some CA in the corners, but only if you're really sensitive to it. Again, it's very easy to correct for that (and on newer Nikon cameras this isn't an issue, since the camera corrects that automatically).
4) Focus: perfect on four different (Canon) cameras, including an old film one. Some might have less than stellar results, but that's only because the lens is more than happy to converge towards infinity, while the depth of field would allow hyperfocal tehnique from only a couple meters. Basically you can set the lens to focus at 3-5 meters away, close the aperture to f/8 and fire away! One special mention: the field curvature seems to be a bit accentuated, so the corners would have a significantly different distance of focus compared to the center. Take care to optimize the focus region for the intended subject, or simply stop down to at least f/5.6 if you're taking landscape pics and the corners are relevant.
If you're looking for an even higher quality lens, Tokina 11-16 f/2.8 is your sure bet; I've tried it, it's as fantastic as everyone says, but if you're using it indoors (at a party or something like that) you might feel it lacking zoom. For outdoor photographers, the 11-16 model is way better; I've used 12-24 for landscapes only at 12mm, basically as a fixed 12mm prime.
Sample for 12mm on a Canon 40D: http://www.flickr.com/photos/bomath/4406436764/
Full size: http://tr.im/TankinaFull (please use it only at home, for printing or any other way, but respect the copyright and don't republish it without my written consent).
BIG BONUS: if you're using a full-frame camera, take off the lens hood and you can use the lens (with full coverage) in the 15-24mm interval.
Check the coverage for 12mm, lens hood removed:
http://www.flickr.com/photos/bomath/4280373124/ (direct scan with a Nikon 9000ED; film: Kodak BW400CN)