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Cons: Mostly plastic housing, at 12mm really visible vignetting, first less sharpness but can be modified(worked for me, see below)

Pros: Extremely wide angel, when adjusted sharp in the corners, very less distorsion, really enjoy this lens. also have the tamron 15-30/2.8, but the sigma is smaller and a bang for the buck.

Summary: I observed when opening and forgot the thin washer, the corners became ugly unsharp. So i assembled it original together and noticed still some unsharpness. So 1 or two more thin washer handled this problem and infinity was really infinity, not like before. Also there are two versions of the first version, with 7 or 9. 7 works on my sigma mc-11, 9 doesnˋt. Have fun :-)

Cons: High rate of de-centered samples, not surprising given the exacting standards required for this exotic lens. Even good samples require stopping down at wide end due to extreme field curvature - as is expected for rectilinear construction so wide. Many users fail to understand the necessary limitations related to extreme wide angle regarding filters and need to stop down appropriately.

Pros: Superb rectilinear accuracy, unmatched among UWA zooms - including the more recent Sigma replacements. Low CA in good copies, especially so considering price and FoV for a zoom. Relatively compact for a FF zoom offering extremely wide FoV. Value priced, especially so for this quality of build, exotic range, and image quality (assuming a good sample)

Summary: Excellent lens design with reviews (and image samples) that span a broad spectrum from spectacular to far below par. Sample variation is the primary culprit, as the exacting standards required somewhat outpace the assembly capabilities implemented. Having tested to divergent samples, the challenge of getting a good sample is clearly the main issue. Bottom line, an excellent lens when using a good copy and good understanding of how to use an exotic lens properly.

Cons: Slightly awkward cap over integrated hood

Pros: Full frame compatible 122° field of view at 12mm Sharp throughout zoom and aperture ranges Little distortion No vignetting Tough build Integrated hood

Summary: Great image quality and super wide view

Cons: The slow aperture can be a problem in low light; Inability to use filters due to the bulbous front lens. Poor design of lens cap which marks the lens shade

Pros: The extreme perspective at 12mm give spectacular results. Its sharpness and lack of distortion from 15-24mm impressive. It has less vignetting and distortion than my 24-105 L Canon The Metal body is well made; solid and heavy

Summary: This is the new upgraded, 2011 version of the Sigma 12-24 and the 2nd I have owned. (The first bought in 2004 for Nikon) I'm using this with a Canon 5D mk 2; a camera which will show up the weakness in any lens. The extreme perspective at 12mm is what drew me to this lens and its giving spectacular results. It’s very much a specialist optic, which needs skill to get the best out of it. Like the previous 12-24 mk 1, it needs to be stopped down to get the best results. At F8 to F11 its sharp; even at the edges at 12mm. At f 5.6 at 12mm it’s a soft at the edges but sharp at the centre. Distortion at 12mm can be a distraction; but at 15mm, barrel distortion is negligible and this is still ultra wide for FF. Used on a cropped sensor camera the distortion is cropped out so expect little or none even at 12mm. Lens flare is not too serious an issue but it will happen in sunlight if you are not careful! I compared the results at 24mm with my Canon 24-105 and I would say without doubt that the Sigma is just as sharp and is more usable as there is virtually no linear distortion at all. The most annoying thing about 2011 version, is the lens cap that is already marking the paint on the metal lens shade after a few months of use

Cons: AF has a problem so I'm mainly using it in MF mode with focus set to infinity, not really sharp, you have to be careful with the front element

Pros: abolutely great wide angle, very low distortion (lower than 16-35mm 2.8L USM), even wide on a crop frame body, feels pretty good in my hands

Summary: I had a LOT of fun with that lens and the angle it offers! Perfect for offering a wide angle "in front" of a 24-70/105/120mm lens!

Cons: Loss of sharpness in the corners 12mm, some (but natural) cornershading, slow

Pros: Extremly wide, quiet sharp for the enormous perspective (specially from 14-22mm and 24mm tacksharp), nice colours (bit warm tipical Sigma), NO distortion, good design and buildings.

Summary: Simply a great lens! Only the Samyang 14 f2.8 comes close, but without electronics.

Cons: Some CA at wider end, vignetting ans sometimes very odd flaring

Pros: Very good distortion handling, reasonably fast AF, Extreme view angle, well built.

Summary: Overall, great lens for architecture, especially good for interior shooting. Also, nice lens for landscapes but you have to be careful about flaring. IMHO, my copy is sharp enough, I am not expecting to be sharp as some prime, but for the widest UWA zoom is absolutely perfect. For the price of used one I believe that this is one the best choices for anyone who needs extreme width. Also, it's good lens for photographers who are using both, FF and crop sensor, on crop it acts like 18-36 which is also very wide. From my point of view, my copy works even better on full frame.

Cons: Not as sharp as I would like, but still very reasonable. Small aperature makes thin depth of field impossible.

Pros: Very low distortions considering the wide angle. Full frame capability. Good contrast which makes images seem to appear sharper.

Summary: I bought this lens so that I can still use it when I change to a full frame camera. I could wish for it to be a bit sharper but the lens has nice contrast making it have the appearance of greater sharpness than might be the case. It's certainly sharp enough and borders on DX anyway don't lag much behind the centre. There aren't many choices for full frame ultrawide Nikon compatible zooms other than the Nikon 14-24 f2.8 which I have only briefly tried. The Nikon will be sharper but is also very bulky, twice the price and almost twice the weight (600g vs 1000g). The Sigma is therefore a good compromise for a keen amateur who won't be making his income from the lens. The size and weight of the Sigma also means it's more likely to travel with me. With that in mind, I'm still very satisfied with my purchase. The very low level of distortion is its strength. The large bulbous front element has never been an issue. It's also very well built for the price.

Cons: Its not cheap, a bit soft from f4.5-7.1 and strong fullframe-cornershading, some CA´s on APS-C and more on fullframe, the frontlens very exposed, no filters.

Pros: Nearly NO distorsion (the guy before is completly wrong with his comment!!!), GIGANTIC ultrawideangel, quite sharp fronm f7.1 as well in the corners. Very good buildings and beautifull color-rendition.

Summary: A very very wideeeeee lens, fantastic perspectives. Quite usefull even at fullframe from f7.1 (before soft). Its a very special item but not without flaws. Very useful for architectism, no distorsion! If you work with Fullframe and loving ultrawide you MUST buy it!

Cons: Soft. Poor contrast. Heavy distortion.

Pros: Extremely good wide angle capacity

Summary: If the wide focal length is more important than image quality it is worth its price. Nothing for pixel peepers.