Product Description

This high ratio zoom lens incorporates Sigma`s original OS (Optical Stabilizer) function and exclusively designed for digital SLR cameras. It is perfectly suitable for low light conditions, indoors, at dusk and telephoto range. 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. The inner focusing system is suitable for using a petal-type lens hood supplied and also circular polarizing filters.

Product Details

• Brand: Sigma
• Model: B000NOSCGM
• Released on: 2007-06-20
• Dimensions: 3.10" h x 3.10" w x 3.90" l, 1.34 pounds

Features

• 18-200mm high-zoom-ratio lens designed for Canon digital SLR cameras
• 2 Special Low Dispersion (SLD) glass elements and 2 hybrid aspherical lenses
• Lens coating reduces flare and ghost; 17.7-inch close focusing distance
• Inner focusing system is suitable for circular polarizing filters and lens hoods
• Measures 2.75 inches in diameter and 3.07 inches long; 1-year warranty

Amazon.com Product Description
The Sigma 18-200mm high-zoom-ratio lens is designed exclusively for Canon 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.

Customer Reviews

Sigma got it right
We've been using this Sigma AF 18-200 lens for a couple of months now. Recently we compared the Sigma with Canon's 28-135mm image stabilized lens on a Canon 30D. We shot side by side photographs at 28mm & 135 mm both, set to ISO 100 with camera in Program mode. Our lenses were set to autofocus with image stabilization on.

The good news which I really didn't expect was to see both lenses produce images that were nearly identical-- I thought for sure Canon's optics would far surpass Sigma's. Color saturation, light exposure through the lens, and detail were indistinguishable. The autofocus worked equally well on both. Both weighed about the same and were about the same size. The Sigma has a 72mm diameter aperture which I liked (so does the Canon). Of course the Sigma is 18-200, and at this time Canon does not have a competing option in the same digital SLR lens class with image stabilization.

The only aspect of the Sigma that differed significantly from Canon's lens was the noise of Sigma's autofocus motor. Sigma produces noticeable motor noise, though it wasn't overly loud. Still if you were shooting in a spot where silence was critical such as a ceremony, it may become an issue but probably not. In comparison, the Canon autofocus motor is silent and fast every time.

Sigma places a locking mechanism on the lens barrel to eliminate any possibility of lens creep (lens extending when pointed down). I doubt this would be a problem with the Sigma anyway. The zoom ring is a little stiff, but not too stiff. The manual focus ring is designed to be used with AF set to off to avoid manipulating the motor when focusing.

The image stabilization works well allowing you to shoot lower light photos without a tripod. I was quite satisfied with Sigma's newest effort here.

I'd say this Sigma makes a great choice for amateur photographers like us looking for a single lens option on Canon digital SLR cameras. The only dissuading factor 'might' be the motor noise if you hope to match Canon's silent motor system. Until Canon produces the same class of lens at a competitive price, Sigma has this round sown up.

---------------------
UPDATE: "LENS CREEP" September 18, 2007
We did just notice the Sigma lens starting creep for the first time (extend while pointed down). So apparently while the zoom mechanism starts off stiff enough to hold the lens in position, over time it will loosen up enough to move on its own with gravity assisting. Still love the lens though.

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.

Winner
This lens is phenomenal. It is the perfect walk-around lens. 28-300mm lenses don't compete, as I find the 18-28mm range to be far more useful than the 200-300mm range for APS-C sensor cameras like the Rebel and 40D. Sigma has an 18-250mm lens, but its lack of image stabilization is a deal-breaker. This lens isn't too heavy, isn't too large, and it zooms like a bastard. If I had to have one lens for an APS-C sensor camera, with cost as no object, this would be it. Second would be Canon's 10-22mm. I would pay big bucks for a faster version of this lens.