Features:

• 18mm to 200mm high-zoom-ratio lens designed exclusively for Nikon digital SLR cameras
• 2 SLD glass elements and 2 hybrid aspherical lenses correct for all types of aberrations
• Minimum focusing distance of 45cm at all focal lengths; maximum magnification of 1:4.4
• Lens coating reduces and flare and ghost; zoom lock switch eliminates "zoom creep"
• Measures 70mm in diameter and 78.1mm long; weighs 14.3 ounces; 1-year warranty

Editor Reviews:

Product Description:
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 the telephoto range. This system uses two sensors inside the lens to detect vertical and horizontal movement of the camera, and effectively compensates for camera shake by moving an optical image-stabilizing lens group. 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 Fully compatible with All Nikon Digital SLR cameras including the D40 and D40x Dimensions - Diameter 79mm x Length 100mm Weight - 21.5 ounces (610 grams)

Amazon.com Product Description:
The Sigma 18-200mm high-zoom-ratio lens is designed exclusively for Nikon digital SLR cameras and is capable of covering a wide range of focal lengths, from wide-angle to telephoto. Two Special Low Dispersion (SLD) glass elements and two hybrid aspherical lenses correct for all types of aberrations, letting Sigma house the extended-range super-zoom lens in a compact and lightweight body that measures 70mm in diameter and 78.1mm long and weighs a mere 14.3 ounces. The new lens coating, meanwhile, reduces flare and ghost--a common problem shared by many digital cameras--while also creating an optimum color balance. Other details include a minimum focusing distance of 45cm (17.7) at all focal lengths, a high zoom ratio of 11:1, and a maximum magnification of 1:4.4.

The lens design incorporates an inner focusing system that prevents the front of the lens from rotating, making it particularly suitable for using circular polarizing filters and petal-shaped lens hoods. In addition, the overall length of the lens never changes during focusing, making the lens convenient to handle and easy to use. Finally, the lens's zoom lock switch eliminates "zoom creep" during transport--a convenient addition when traveling. The lens, which includes a metal mount, is backed by a one-year warranty.

Rating : - Comparing the Sigma to the New Canon 18-200mm IS Lens
I've had the Sigma 18-200mm OS lens for several months and found it to give sharper images with my 40D than the Tamron 18-250mm (non-IS/OS) which it replaced. Then along comes the new Canon EF-S 18-200mm f/3.5-5.6 IS, their own superzoom "travel lens." I bought one to see how it compares to the Sigma. My tests show mixed results regarding image quality. With both lenses wide open the Sigma wins at the wide end from 18-24mm, especially away from the center, while the Canon wins at the 135-200mm long end, also especially away from the center. The Sigma is f6.3 wide open at 200mm while the Canon is f5.6. This is only a small difference, but it does give the Canon even more advantage at 200mm where shutter speed needs to be the highest.

Both lenses auto-focus accurately (no front or back focus) although the Sigma is slower to lock focus in low light and is a little noisier in getting there. Their IS/OS are equally effective at about 3 stops of compensation. Build quality, size and weight are about the same and both use the same 72mm filter size. Sigma includes a lens hood while Canon wants to sell you one.

In summary, the Canon is slightly better for me due to the faster and quieter low-light focus and improved telephoto image quality. The trade-off is poorer image quality than the Sigma for wide angle shots, even after stopping down. Finally, the Sigma lens costs about $200 less than the Canon at this time.