sigma

Filter Size 77mm
F-Stop Range 2.8 - 32
Minimum Focus Distance 72" (6')
Magnification 1:7.8
Zoom/Focus Control Two-Touch (Twist)
Angle Of View 43.3 (70mm) - 12.3 (200mm)
Groups/Elements 14 / 17
Length 7.1"
Max. Diameter 3.4"
Weight 49 Oz.
Specialties "Hyper Sonic Motor" For Quiet And Smother AF, Instant Manual Focus Override In AF Mode, Low Dispersion Glass, Non-Rotating Front Ring, Tripod Collar

I have owned this lens for about a year now in the Canon EOS mount. When first considering this lens, I debated over buying it or the more expensive Canon version. After reading numerous reviews, it was obvious that many other users felt this to be a great lens, comparable to Canon's, but at a much lower cost. So, I decided to get the Sigma version. I have never been sorry for that decision.

I should note that I have used both this lens and the Canon equivalent, so comparisons can be drawn from this. I have not used any comparable Nikon or other lenses in this focal range.

This lens allows for great versatility. There are numerous scenarios in which this lens performs well. Below are just a few.

Positives
1) The 2.8 aperture allows for great low light photography, or dusk/dawn outdoor photos
2) In the 85-135mm range, the constant 2.8 aperture makes this a very good portrait lens; throwing the background out of focus and making the subject stand out.
3) With the Sigma 2x APO teleconverter, this lens becomes a very nice 140-400mm 5.6. It will still autofocus with all Canon EOS bodies, and produces sharp photos despite the 2X converter.
4) High Speed focusing motor, rivals Canon's USM technology
5) APO, low dispersion glass produces top quality images with clear, contrasty images
6) Full time manual focus
7) Tripod mount is included, something that Canon will make you pay for...
8) Very sturdy lens design, solidly constructed

Negatives
1) Tends to hunt just slightly more than the Canon Version. This is easily overcome with full time manual focus
2) When the hood is attached in the "storage" position (reversed on the end of the lens) the full time manual focus ring is hard to manipulate
3) HSM is just slightly slower than USM (Canon's ultrasonic focusing technology)
4) Lens is heavy, but so are all similar lenses. I suggest a monopod if prolonged use is expected

...

Sigma also has a new 100-300mm F4 lens that is similar in quality and design to this 70-200mm version. If you tend to stay at the longer focal lengths and don't need the extra 2.8 f stop, then I would suggest looking into the 100-300 F4 lens that is new to the market.

Overall, I am very happy with the performance of this lens. In my opinion it is well worth the price tag and with the money you save over the Canon version can be spent it in other areas. I used the extra savings to purchase the 2X teleconverter and a few 77mm filters.

...Thanks for your time...