I agonized over the decision about whether to buy the Sigma AF 18-200 DC OS. The on-line sites (such as dp) showed softness at the edges, particularly with the f-stop wide open. There were criticisms about the focus ring being easy to confuse with the zoom ring. There were complaints that the optical stabilization isn't state of the art. I bought it anyway because I was looking for a super zoom that could do wide angle, but also go all the way to decent telephoto in a single lens and offered optical stabilization so those telephoto lengths would be usable hand held and couldn't afford Nikon's offering in this focal length range. I have been tremendously impressed with the Sigma AF 18-200 DC OS. The optical stabilization is quite dramatically noticeable and makes a big difference. Low light shots in the 18-55mm range that I would never have got away with with my kit lens are distinctly do-able with the Sigma - despite it's extra bulk. Telephoto shots in indoor lighting situations are fine too. Subjective sharpness is fine. The softness the reviewers note in the corners isn't subjectively noticeable in the pictures my Nikon D50 is taking - at the screen resolutions I'm viewing (and posting). Color saturation and contrast appear superior to the Nikon 18-55 kit lens I'm replacing - and subjective sharpness is at least as good.

I was worried that the bigger Sigma would be a big adjustment. It's definitely bigger than the 18-55 kit lens - but it's not a big adjustment. I had to get a bigger case and I added a hand strap: (the inexpensive and very usable  Opteka Professional Wrist Grip Strap for Digital & Film SLR Cameras ). I'm quite happy with how this rig handles.

So why only 4 stars? I dock a star for the focus ring issue (the focus ring is a bit prominent and has a very similar looking and feeling grip to the zoom ring). I wish the focus ring had a more clear tactile demarcation (maybe a diamond pattern, instead of the same kind of ridges the zoom ring has - for immediate tactile recognition). As it goes I usually stow the lens hood backwards for storage and this overlays most of the focus ring - forcing me to grab the zoom ring. I also dock some because it has some issues acquiring focus at longer focal lengths in low light. This is a bit of a quibble because the kit lens also has issues acquiring focus in low light, but the situation is a bit worse with the Sigma zoomed out. All in all I'd give close to 4.5 stars given my general level of satisfaction.

The Sigma AF 18-200 DC OS ultimately does everything I wanted. It provides a single lens solution to the vast majority of shooting situations. It provides very acceptable image quality. It provides usable image stabilization and decent ergonomics which make it usable in a wide range of circumstances. Bottom line, this lens turns my camera into a much more powerful tool. I wonder why I waited so long?

After taking long and hard look on Nikon D5000 and its "kit lens" 18-55mm zoom lens, I was convinced that I needed something more powerful to have it on as daily lens and avoiding having to swab out lens frequently, or worse, in between crucial moments when you should be busy composing and taking shots of objects from multiple distance. Naturally, Nikon 18-200mm was the first choice, but after seeing rather substantial price difference, I decided to take up on dpreview's review on this lens (overall verdict was very similar to Nikon's) and save money (1/2 price compared to Nikon) and use that towards other goodies (Flashlight, prime lens).
I spent 18 months taking pictures using this lens as my every day lens, almost 8000 shots and I can confidently say that this type of super zoom lens should be what everyone should own as their starter lens. I am sure professionals would own multiple lens and something far more expensive for their needs, but for everyday Joes, hobbyist and novice, this is more than anyone can ask for.
It is by no means Macro lens and I have run into times where I would have to step back in order to take shot (I was too close to the object), but you can easily compensate that with zoom. Image can be soft at certain distance, but it is mostly non-issue unless you are scrutinizing it carefully. Built-in pop-up flashlight on camera will be an issue as it protrudes too far and will cast shadow. Using external flashlight is highly recommended, but being creative with other settings to avoid using flashlight will be fine. It is a fine performer in places with ample lights, and saves many shots in darker environment with built-in OS function. AF can be bit slow at times and sometimes lost track of what it is focusing and end up focusing on wrong object, but you can easily override that.
As many other super zoom lenses, it does create distortion in different levels (due to limitation of design), but with programs such as Lightroom, you can correct distortion as well as chromatic aberration. Added bonus of using this type of super zoom lens is that you can use it as passable wide angle lens (18mm, 24mm on Nikon DX camera) and cover more area.
As a DSLR newbie, I was shocked at how heavy whole camera was with this lens on it, but now, it feels more of that reassuring heft than anything else. Happy snapping! You won't regret this as your first lens.

I did a fair amount of research before buying this lens, but I was having trouble with dirt getting into the camera as I was constantly changing a 18-55 and 50-200 lens. The reviews suggested it was much clearer than the equivalent Tamron. I have owned it for 10 months and am very pleased with the results. No point comparing it to a £900 canon or nikon monster, but it is very capable. The 200mm reach is very handy and the image quality is actually pretty good wide open at that setting. At 18mm it is decent as well, but benefits from stopping down a little. At this wide angle setting it also shows much less barrel distortion than my Pentax kit lens (but I wouldn't tell the Pentax fan-boys that ;-) More than capable for general use. Solid enough and does not seem to have too many problems with focus.

I purchased this lense after much deliberation against the much much higher priced comparative . Although I had several farcical events starting with the wrong lense being sent which made me think I was not meant to have it, however these things happen and the seller was positive and re-acted honestly to get things sorted out.
I eventualy received the correct lense and put it straight into work whilst Iam no expert I must have taken and viewed over 50 or more photos with the lense over the first weekend I used it .It has a nice feel and looks the part on the camera it looks clean and sharp and in no way looks anything other than a quality lense from the out side.Fits well to the hand and the controls work cleanly and smoothly
Pictures I took varied from the family groups,portaits of the kids Wife and dog including close ups and wider views. I printed some of these out on A4 size paper the results in my opinion as good as those in reviews of other named lenses that Ive seen when going from site to site and certainly good quality.
When attempting to use the lense as a macro / close type photos of flowers ,rocks,and insects I had simlar pleasing results.
The camera needs good light and sometimes needs a bit of fidling in low light conditions
I put this down to the size of the lense but when using only the built in flash again the pictures are of good quality.
I was warned of the failing of lense creep with such lenses but I can say not once have I experienced any at all either using the camera pointed downwards or upwards for long periods
All in All I have not to date been disapointed with the results and since I didnt have to pay twice as much any niggles with it seem acceptable
If your dwelling on this lense for the money at the moment I cant fault it and probaly in the hands of a more proficient camera person the results obtained would be even better
Iam I pleased I bought it most certainly yes

This is a quality lens but that goes without saying as you can expect nothing less from SIGMA!!

Pros:
Its perfect from macros to zooms, well built, smooth movement with crystal clear optics.
Comes with a handy petal-hood for outdoor shooting.
When zoomed in, the lens is not as large as the Tamron or the Nikkor (the latter not being applicable to Sony Alphas)
Using an all-in-one lens means no fussing around detaching and re-attaching!

Cons:
No in-built image stabilization (like with the Nikkor's)
The 'hold' button can only be used at its widest setting.

You take your kit-bag, laiden with the film-version of a s8mm; 35mm, 50mm, 105, 135, 200, and 300mm - and question yourself, "Why?".

Why indeed: this ONE lens covers all those focal lengths (and the ones in between). And there's no likelihood of you getting dust on your sensor every time you change your lenses because you simply don't need to change unless you need a super-wide or a true macro, maybe a big telephoto.

Money well-spent. I have it on a Sony 580 - so I didn't even need the image-stabilised version, saving more money!

Check out the 'Sigma' set in [...] - some are shot with my 105mm macro: the rest with this lens. And no tripod!

I use two cameras and I leave this lens on one camera all the time. It is very versatile and covers most situations. At both ends of the zoom there is a slight drop off of sharpness but nothing to worry about. When I first used it the zoom was fairly stiff and this has now gone and was only because it was new. There is a switch which locks the zoom while not using it or walking with strap over neck.I am a club photographer and would recommend this and all the Sigma range.

Bought this lens for a holiday in Italy. It has exceeded expectations far better than lens that came with camera. Yes it has shortcomings at extreme ends of its ranges and F stop. But if you are a serious amateur photographer then using Lightrooom should be a serious consideration, as this lens has a profile built in which corrects any noticeable aberations. So with the software this lens is excellent and I like the results. Worth every penny!

Bought this for My Sony Alpha 230 so that I can take it on holiday without worrying about changing lenses on the beach. That was the intention - a once a year use - but reality is that it is constantly on my Sony Alpha 500 simply because it is so versatile I tend to use it every day, only changing to a prime lens when absolutely neccessary. Excellent value for money!

Hi,

Got this about a year ago now been using it allot. It came well packaged no problem there,
it came about a day late though. It came with a sunshade. It was easy to install.
I find it great for long distance shots for really close up picture it's not bad but I recommend
something specialized for close ups. otherwise very good lens. If you go about with more than one
lens it easy to take on and off so you don't have to worry about having to make quick changes if needed.

I bought the 75- 300 lens to go with the 18-75 standard lens,--.MISTAKE.
This lens is more versatile & can stay permenantly on the body, the zoom
is better to control & my results so far have been very acceptable for an
amateur. If you get a filter remember that it is a 62mm thread

Great lens, focus and aim is great. A little noisy at times & doesn't perform well in the heat struggles to focus a bit but nothing a little flick off of the power button can't handle. Good quality well made and has taken some amazing pictures at close and long range

excellent

Good focal range to save changing lenses. This lense has been permanently on my camera since I bought it to stop dust creeping in when lenses are changed.

This is a good lens and good value. Works well on my DSLT and my DSLR. But I have since invested in a 300mm and the difference is amazing. This doesnt get close enough for those Wildlife/airshow pictures!

This Lens has extremely served me well since purchase, I am more than happy with my decision to buy it.

Excellent:-)