Sigma 10-20mm ULTRAWIDE zoom for Nikon DX

The Sigma 10-20mm I am evaluating is one setup for use on a Nikon DX format Digital SLR. The lens I purchased came well packaged with a very nice custom case, and a small lens hood. Overall, a very quality appearing package.
This lens is primarily used on the D200 body, and the results with this combination are fantastic. I looked at the Tokina 12-24, and the Nikon 12-24 as alternates before choosing this lens. I chose the Sigma because it was the least expensive, had a great build quality, gave exceptionally sharp images, and had the widest setting of the three options.
This lens is very forgiving. It focuses fast and accurately. It has great contrast, and gives exceptionally sharp images on the D200. Many lenses on this high resolution body can not produce the fine detailed images due to the extremely precise 10MP DX sensor. A poor lens will not give sufficient resolution to perform well with this sensor. This lens does not have that problem, and is well matched to this camera.
This lens has exceptionally good resistance to flare, and has minimal distortion, as long as you follow a few rules on Ultra wide angle shots. As with any wide angle lens, the framing of the image is important to producing visually appealing wide angle shots. If you want to maintain perspective with a wide angle lens, be sure to line up straight edges perpendicular to the frame edges. The lens orientation needs to be held square so building walls are truly perpendicular in the frame, or the resulting image will have an unusually distorted look to it. This is not something that is exclusive to this lens; it is a fact for all wide angle lenses. It is just that this lens, at 10mm is wider than most, so the framing issue is even more critical. Unless you really want walls to look bowed, and faces to look distorted. Might give some interesting artistic images.
The Sigma 10-20mm is the ideal lens for people who want to cover as WIDE area of view as possible. Most people do not realize how wide 10mm is on a DX format Nikon. The field of view is so wide that people off to the side of the picture are not even aware that they are in the field of view. If you have big feet, be prepared to see them in some wide angle shots. 10mm really does give an interesting perspective to photographs.
The 10-20mm focal length is ideal for those who are looking to shoot indoors. It is also an ideal lens for truly wide area landscapes. The only downside to this lens is it is not a real "fast" lens, as it does need relatively good lighting to produce the best results. Another item to note is that most on-camera flashes can not cover a wide enough field to light the entire image at the 10mm setting. You will need an external flash on the Nikon if you need flash photography at wider than 14mm settings.

My copy had no defects, and the build quality is comparable to the Nikon lenses I own. I would highly recommend this lens.