Customer Reviews
Sigma made a fine lens- New HSM motor is wonderful! 
2008-08-21
I just purchased this lens and received it yesterday, AUG 21. What I can say from my initial impression is that I am very glad that I purchased it! the writing is on the wall with the reviews, just go look them up, but here are the key points I notice:
-NEW HSM MOTOR- VERY QUIET! I have read reviews about the "old" micro-motor that was in the earlier copies of this lens being a distraction, the new HSM one is silky smooth and AUTO FOCUS IS QUICK. I would not hesitate to take this to a wedding, ceremony, library, whatever
-Autofocus is quick! Had to repeat that one, no hunting here, from wide to tele, I have not had any problems, even in low light, low contrast it does very well. I have been very happily surprised
-It is pretty heavy! Be prepared to have a work out with this one, although compact it is DENSE, hopefully a sign of quality (which seems good to me). As a wonderful walk around lens, this one will get your arm in shape- mine hurt after about 1 hour of shooting handheld.
-The zoom ring is a bit tough to turn (very very well dampened)- The NIKKOR is much easier and smooth . . . and tends to creep a bit from what I have read (although I didn't notice it). I feel confident that this lens will not creep- you are going through a huge zoom quickly, so I cannot say this is a detriment to the lens user, just takes some getting used to. This is not an issue that I would pay $200 to correct.
- As others have noted, the VR is a bit loud, but not really LOUD, just louder than any other VR type mechanism I have heard, which is to say that you cannot hear it from more than a foot or two away
-Color, contrast are great, I couldn't ask or more in these categories
-Bokeh, this is subjective, but I find the bokeh to be neither great nor poor. It isn't beautiful or distracting. Nobody I know would buy a zoom for this anyways.
Read the reviews for all the technical stuff, to me this thing is very capable of making great photos. If I were a new DSLR user, this would be my first lens. There are very few gaps that this lens leaves behind. It replaces nearly every lens I own, or want to own.
Overall, I find the barrel distortion to be the biggest drawback, and really only at 18mm- I use Photoshop to correct this when needed, to great effect.
I would highly recommend this lens.
WARNING: THIS LENS WILL MAKE YOUR CAMERA HARD TO PUT DOWN!!
:)
Perfect walk around lens 2008-08-19
I love the performance. Best fits wedding shoots. As an amatuer, with one body, it lessen the time of changing lensen, unless very neccessary. for me i love it.
An Excellent Buy 2008-08-14
This lens will be on my Nikon D40x permanently. Ease of use, quality of results, flexibility - landscapes, family portraits, it ticks all of the boxes. I'm a very satisfied customer.
3.5 would be more accurate 
2008-08-02
I have had this lens since 9 July, and used it without incident until 25 July, when the OS failed. Up to that point, I would have given this lens a five-star rating without the slightest hesitation. The distortion control, as well as the sharpness on the first sample were excellent. Furthermore, the focus was accurate to a T in all situations, including very low light.
The replacement lens, which I have now used for about a week, does not have nearly the same sharpness at the edges. It is fine in very bright light, but in dimmer situations, both the sharpness, and the focussing ability, are not up to the standard of the first sample.
I also find that the OS on this sample does not give the same f-stop compensation as on the first one.
This said, the lens remains a good one, and I would still recommend it for use with the Nikon D40.
Whether or not I will retain this one, or again request a replacement based on the less than stellar focussing ability in low light/low contrast situations remains to be seen.
excellent lens 2008-07-29
I have tried many lens with my 40D. I like the 18-55mm IS kit lens. It's probably the sharpest standard lens that Canon ever made. 28-135mm IS is also good, but lack of 18-27mm zoom. I sold it and bought the Sigma 17-70mm and Sigma 18-125mm OS. I returned 17-70mm because I have shaking hands and most of my photos are indoor. I also returned 18-125mm because it produce very very soft and lack of contrast. Almost like older P&S digital camera. I then bought the Tamron 17-50mm f/2.8. Hoping the f/2.8 will help with my shaky hand and indoor situation. I return it after compare to my 18-55mm IS. Not worth the extra $300 for Tamron for the same zoom. Finally, I decide to buy the Sigma 18-200mm OS after reading many positive and negative reviews. To my surprise, 18-200mm is very sharp lens in ALL ranges. I read that lens can be soft at certain zoom. I have tried for a week to try to find the soft spot, I can't find it. The only thing I noticed is the "strong" OS motion. I can really see the OS kicks-in. I was surprised that I got almost all keepers in my "walking" shots. Highly recommended. I don't know if any lens in this range can be better, especailly with OS.
Good lens for the money 
2008-07-17
The Sigma 18-200 F3.5-6.3 DC OS HSM Lens incorporates an Optical Stabilizer function and is exclusively designed for digital SLR cameras. It is perfectly suitable for low light conditions whether indoors, at dusk, or in telephoto range. This system uses two sensors inside the lens to detect vertical and horizontal movement of the camera by moving an optical image stabilizing lens group, to effectively compensate for camera shake. It also automatically detects panning movement of the camera and compensates for camera shake when shooting moving subjects such as motor sports. SLD (Special Low Dispersion) glass and aspherical glass provide excellent correction for all types of aberrations. This lens has a minimum focusing distance of 45cm (17.7") throughout the entire zoom range and has a maximum magnification of 1:3.9. Since the inner focusing system means the front of the lens does not rotate, optional circular polarizing filters and the supplied petal-type hood can easily be used. A magnification scale is displayed on the lens barrel, ensuring ease of use. A zoom-lock switch mechanism is provided to prevent the lens from creeping due to its own weight. 69.3 - 7.1 degrees (Sigma SD format) angle of view 7 Diaphragm Blades F22 Minimum Aperture 45cm / 17.7 Minimum Focusing Distance 1 - 3.9 Maximum Magnification Petal Lens Hood Dimensions - Diameter 79mm x Length 100mm Weight - 21.5 ounces (610 grams)
Sigma 18-200mm Image stabilization, for Canon 2008-07-11
I bought the lens to give me more range without changing lens. Does the job. I bought it right before I went on vacation. Took a while to get use to it. Makes very good pictures at all ranges. I found that I didn't need the 200mm, except for rare occasion. The Image Stabilization was what I wanted since I could not use a tripod on vacation. Only a few pictures showed movement. Even used it in helicopter ride. Got some good pictures.
The only problems I had were the weight. It is heavy for me. Carrying it all day gets tiring. The barrel is quite big, but know it is the I.S. There is some lens creep, had to use the lock. One thing that was hard to get use to was grabbing the focus ring with it in auto focus. The ring is too easy to find.
Overall, it is a good lens. Picture quality is good, and price is good. Good general use lens.
Sigma AF 18mm-200mm review 2008-07-10
This is a great lens. My wife is a newspaper photographer/reporter. She uses this lens as her primary walk-around. The 18mm-200mm range gives her a great deal of flexibility without having to carry extra lenses and go through the lens changing dance. Imagery with this lens is first rate. The optical stabilization works like a charm. We use it on Canon 30D and 40D bodies. You can find some low-res images here:
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Great Lens 2008-06-29
I have this lens for almost two weeks and I took already almost 500 pictures. The zoom works very prezise and the optical stabilzer is amazing. I took some pictures inside a church and didnt have my tripod with me. All pictures were in focus.
Outstanding Lens! 2008-06-11
I don't know alot about lenses but my wife wanted this for her birthday. I purchased off of Amazon and my wife loves it. The only drawback is she says when she's taking pictures in public it makes her look like she knows what she's doing. HAHA!
