Summary: Here is the problem with mega zoom lenses. You will NEVER get a sharp image out of it. plus you need a ton of light to even use the thing. Do yourself a favor, get smaller range lenses. 70-200 and 24-70 if you need something wider then get that too. Do not buy.
Description should say it is not for full frame DSLR's
14 January 2013
Summary: Well, I just ordered this lens today from Amazon.com, based on the reviews here it sounded like a good lens for a decent price. The description of the lens sounds great. The problem is, the description of the lens on Amazon.com does not indicate that it is not for full-frame FX format cameras.
Excerpt: The Sigma lens mounted properly onto the 5d. But due to different lens construction, the plastic casing created a vignette around the picture frame at all zoom lengths. Also, when zooming it would snag and not go in and out smoothly. Not recommended for the 5d.
Cons: Constant Vignette, Lens Creep, Slow Focus, Zoom not smooth
Summary: I purchased a Sigma 18-200 zoom lens and after a week of testing and comparisons I sent it back. Fortunately Amazon has a swift no quibble returns policy. Sigma's lens failed because the images were soft and focusing problematic. The lens also started to rattle.
Summary: I am a amateur and new to DLSR's however I bought this for My Nikon after reading numerous mixed reviews all over the internet. At £280 it was worth a look; considering the Nikon equivalent is £700! The recommendations suggest this takes a 72mm filter - it doesn't, its the newer 62mm version.
Summary: Habe mir das Sigma 18-200mm II DC OS HSM vor 7 Monaten gekauft und war damit durchweg zufrieden. Auf die geringe Lichtstärke lässt man sich bewusst ein und von den teilweise dramitsch beschriebenen Verzeichnungen habe ich nichts bemerkt - zumindest nicht so negativ wie es manchmal beschrieben wird.