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Cons: Corners are very soft at the wide angle end. Quite a lot of chromatic aberration with high contrast objects. Claims to be a "Macro" but isn't really.

Pros: Great zoom range. Good centre sharpness, and good sharpness everywhere away from the wide-angle end, and stopped down a couple of stops. OS works well. Maybe not giving the 4 stops that SIgma claims, but definitely worth 3.

Summary: A fine, versatile general purpose lens, that is very usable hand-held. It can produce top quality results at focal lengths above about 20mm, when stopped down. However, anyone looking for something to use wide open and/or at extreme wide-angle, or that needs macro capability should look elsewhere.

Cons: Zoom ring abit tight. produce annoying sound while focusing.

Pros: lens feel very solid,,good image sharpness..nice aperture f2.8-4...versetile focal range.,able for close focusing just 5cm when use 70mm..

Summary: u got what u pay..this lens is ideal for daily use..suitable for wedding, travel, landscape, close focusing..very satisfied

Cons: you allways want faster aperture, or more efficiant optical stabilizer, but for the price it's not really a cons. when I want eide open aperture for longer focal length, I use my sigma 50 1.4 EX DG HSM. thats more than OK for me...

Pros: the optical quality is great, the range is perfect. there is wide-open 2.8 aperture at least for 17mm, also stabilizer and HSM system, quiet and fast. I love the 17mm. besides the 2.8 this is great angle of view.

Summary: this is my primery lens. maybe it's not the most perfect lens, but for 450 USD brand-new, you should never compare it to canon 24-105 or so on. I'm really happy with it.

Cons: Not the sharpest.

Pros: fast focusing, wide aperture for zoom lens. Close focusing

Summary: Good build quality.

Cons: No full-time manual focus

Pros: Very useful range, quite sharp overall, good image stabilization

Summary: A very nice walk-around lens for crop sensored cameras

Cons: No full time manual focus a little heavy

Pros: Amazing sharpness Great range Very fast and accurate AF

Summary: The best all in one lens for price, no doubt about it, at the condition to get a good copy.

Cons: There are sharper lenses, though I find it very sharp for my use.

Pros: Very versatile, fast, sharp, silent and accurate AF, low CA, solid build but not to heavy.

Summary: Best all around lens on the market at that price point that doesn't have massive CAs or low resolution like most of the 18-2*0mm breed.

Cons: --

Pros: very sharp good OS nice colors

Summary: Very good kit lens replacement

Cons: has focusing issues under low light conditions even with an af assist light. HSM motor not as "silent" as advertised

Pros: good image quality and good color reproduction. the images produced are often quite vibrant but minute detail is lost compared to some canon lenses on the market including the almighty 50, of course those lenses are much better. it also has a very useful focal range

Summary: a very good lens for its price, but if you have a copy that has focusing problems and you do not know how to quickly adjust the lens manually you will lose many good shots in low light conditions. otherwise its a great lens

Cons: Now on my third lens, The first two where soft in the corners but sigma Japan have just replaced the second one under warranty and i have to say its perfect.

Pros: This one is killer sharp all over the frame, Its just a shame that it took three lens to get one good one.

Summary: At last i can see what everyone is raving about. Very very sharp with great OS and good focus system.

Cons: Soft in the corners, This was my second lens changed for the same reason. Thought i would send it in for repair rather than exchange, That was 8 weeks ago, Its in Japan!!!.

Pros: Very quite and fast A/F. Good OS system. Nice range

Summary: My Pentax 18-55wr is Sharper in the corners. Lets hope its better if it ever comes back.

Cons: Visible distortion on the ends of the focal range. Lack of full time manual focus, the manual focus is delicate - one needs to get used to it. Soft between 60-70mm

Pros: Great range. Fast apertures comparing to other lenses with the same focal range. Very good picture quality from about 22 to about 45 mm Useful Auto focus. Effective image stabilizer. Low price.

Summary: All considered, it's the best lens of that focal range you will get for the price. A perfect lens for a beginner to learn on before getting much more expensive equipment. In the mid range it can produce photo's that will scratch professional quality, especially if you step down a little. However, going pro will demand better glass, for twice the price.

Cons: no FTM, vignetting is noticeable,slight color fringing on widest end.

Pros: sharp wide open f2.8, superb center resolution, good corner to corner performance, macro ability, great 17-70mm range never leaves body. works very good against bright lighting, well controlled color fringing after 24mm. round and smooth bokeh. 7 rounded aperture blades. fast quiet AF with HSM.

Summary: super sharp macro lens with a fantastic zoom range. the only gripe i have is the lack of full time manual focus and it doesn't feel as robust as the sigma EX line of lenses.

Cons: Slight horizon distortion at 17mm setting, but nothing serious.

Pros: Sharp, fast and quiet.....brilliant value for money. My Sigma 17-70 has not shown any evidence of vignetting at all. A decent close up lens but not a true macro, but very good nevertheless!

Summary: This is a super walkabout lens that does not break the bank.

Cons: OK, velice ostrý, v některých rozsazích srovnatelný s pevným sklem.

Pros: OK, velice ostrý, v některých rozsazích srovnatelný s pevným sklem.

Summary: OK, velice ostrý, v některých rozsazích srovnatelný s pevným sklem.

Cons: Heavy compared with plasticky kit lens from Canon.

Pros: 2.8 at wide end closing to a respectable f4 at the tele end. Excellent OS that produces consistently sharp hand held results. Smooth focus, fast and accurate. Very decent bokeh. Macro feature good for casual closeups--added bonus to what I believe is excellent value. I do not see any CAs until the image is blown up to an extreme level on my computer. Moderate distortion at the wide end may not suit precise architectural photography but then why buy a general purpose zoom for that sort of work?

Summary: I would buy again if lost or stolen.

Cons: Not a constant aperature. Slight vignetting

Pros: The focus very fast and accurate. Very good center picture quality.

Summary: A good walk about lens for everyday use. Solid build quality for the price point.

Cons: Vignetting No constant Aperture

Pros: Good image Quality

Summary: My favorite All-round Lens!

Cons: Field curvature at wide angle. Slight CA.

Pros: Sharp. Very sharp stopped down a bit. OS works. A little faster than most others. AF reasonably fast.

Summary: Good choice for all around lens.

Cons: - No full time manual autofocus - Focus ring turns only 60° or so, difficult to focus manually - (Suspect) production quality issues, many people report front/back focusing

Pros: - Excellent image quality (stopped down), good quality even wide open till 50mm - Good and fast autofocus (comparable to Canon's USM) - Good IS (again comparable to Canon's) - Decent build quality, no zoom creep (and lock switch provided, unlike Canon) - Fast for a zoom with this focal range - Not macro but VERY close focusing - Cheap, and hood included (shame on you Canon!)

Summary: I don't understand the bad user reviews lamenting softness.. in the range 17-35mm this lens is super sharp, and for the rest is still very sharp if stopped down 1 stop. So the softness problems some people is experiencing must be front/back focus i guess.. something they should ask Sigma to fix. Before buying this lens i compared it side by side (shooting resolution charts) with the highly regarded Canon 15-85mm, my old Canon 17-85 and Canon 50mm prime which is also super sharp. The Sigma matched or slightly exceeded (short range) the Canon 15-85mm AT THE SAME APERTURE at all focal ranges, it doesn't make sense to compare the two lenses always wide open because the Sigma is one stop faster at all focal lengths. Wide open at long focal lengths it is indeed a bit soft, but a soft F4 is still better than no F4 (and it improves a lot already 1/3 or 2/3 stopped down). As for Chromatic Aberration, it's present only at the shortest focal length, but the same is true for the Canon 15-85; if you want to see a lens with CA problems, look at the Canon 17-85 which is plagued in the whole focal range (and it's softer than the Sigma too). This lens has L-class image quality (if you get a properly calibrated auto focus) at a bargain price!

Cons: Chromatic aberration = huge problem. Some flare problem.

Pros: Cheap all-round lens. quick and correct auto focus. Good optical stabilization.

Summary: Shoot 900 images indoor, narrow space. 400 images @17mm. All need to apply lens correction filter in CS.

Cons: Very warm colors comparing to standard Canon 18-55 IS. Heavy. Slow focusing in low light. Soft Picture quality. Visible distortion.

Pros: Macro

Summary: Was expecting better quality of the pictures.

Cons: Slightly soft picture what doesn't fortunately come as obvious with 6Mpix sensor (Nikon D70) what it would be on 12Mpix or so on. Manual focusing ring is little narrow on its turning range, so getting it sharp takes steady hand. What really annoys is the the zoom what rotates wrong direction for me. This is of course individual broblem, but it seems after month still difficult to fit it back of my head...

Pros: Tracs focus very fast and accurate (backfocus IS fixed from the body). Can't get from stabilization quite that 3 EV improvement what promised. Surely 1 to 2 EV advantage on real situations has come apparent. Light passes trough nicely on wide end - would be great lens if that happened on another end too. Guess that would cause more softening on images and other optical difficulties.... For me the macro is really positive surprise! It focuses really close on 70mm end. Haven't measured but somewhere close as 2 cm. On smaller aperture it really gives nice details and works fluently! OS doesn't seem to shorten battery life noticeably what is really nice thing to discover!

Summary: Nice piece for lower resolution sensor. Not too much to complain about this other than price... Anyhow, I am pleased on this lens. I was looking one lens to rule all sitatuations and this is it for me. I can spot the possible faults on optical quality on this if you want to go really pro... softening and all. But this is not too big of a compromise to get good photos with one lense. I'm planning to keep this!

Cons: -White markings on the lens can be scratch off easily. Mine got scratched off just by thumb nail while changing AF to MF. -Heavy even on my Canon 50D -Backfocusing problem for mine -Not accruate focusing in low light, slight hunting occur. -Colour too warm compared to my Canon lens. -Very soft picture quality after 50mm. -Soft picture quality when wide opened. -distortion quite visible at 17mm -Macro focal length too far to be considered as a Macro lens

Pros: -Good Focal length and aperture range. -Fast and silent auto focus. -Very good center picture quality -Little chromatic aberration -OS and Macro

Summary: Overall a very good all round lens in the market. if it didn't backfocal on my 50D i would have given it a better score.