Sigma AF 18-200mm f/3.5-6.3 DC OS (Optical Stabilizer) Zoom Lens for Canon Digital SLR Cameras

This is the second Sigma Lens I've owned and the second one I've returned. Common to many Sigma lenses is zoom creep, inaccurate focus, and heaviness. The reason I give it 3 stars?? If you use your DSLR more for snapshots and need a huge zoom range this lens is a good alternative to carrying two lenses or spending $600 on the Canon equivilant. If you want your pictures to be in focus and have a lighter lens, smoother focus ring and have some extra money in your budget, go with a Canon lens

I have used this lens with my D40 for about a month. I was concerned about the relative slowness of the lens, especially at full zoom, but the OS makes up for it allowing me to shoot successfully at slower shutter speeds. Optically the lens seems fine to me. It DOES autofocus with the D40. Combined with a Sigma 30mm HSM prime lens, I have everything I need for most situations. This lens is significantly larger and heavier than the Nikon kit lenses. You will know that you have this 1-lb lens hanging around your neck! I am very satisfied with this lens. Recommended to replace both the 18-55 and 55-200 Nikon kit lenses.

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.

I bought this lens when i bought my Canon XSi back in May. Its a great "walk around" lens. it covers a huge spectrum of range. For daylight photography and with a flash it works very well. My only real complaint is that its heavy and a little big... but this is expected with the 18 to 200 range.

IS works very well. At the 150 to 200mm range there is a noticeable difference between IS turned on and Off.

pared with the canon 50mm f 1.4 i think i have all the glass i'll need for a while. now its just a matter of learning how to use it well.

Lens is great. Can hand hold 200mm focal length at 1/30th sec shutter speed(without camera blur),when using the optical stabilizer. Would higly reccomend this lens. Rarely comes off my camrea. With 18-200mm focal length and the OS it is pretty much the only lens you will ever need!!