Stef- trying to quote the Canon Dealer on his statement regarding unbranded lens. Something like"... we know what algorithms we use in our cameras, and why and how we designed them the way we did. Everyone else is guessing, and will sometimes get close. But not on,"

There are snobs out there who will judge you poorly for buying non OEM. You just have to decide if their opinion will affect you or your business, or if you even care about their opinion.

That being the official line, I think you have to judge the results of the lens. Read reviews by other users, and maybe rent one and see if you like it. I personally buy OEM glass, and the top of the line that I can afford. But everyone has their own sets of standards they buy to. Buying the fastest lens you can is the first step, and then you buy the best l;ens you can. Beyond that, I have no issue with Sigma, and have no awareness of deficiencies in them for pro users. And that range is a well thought out range, with good usability. If you know someone who has one, borrow it and test the lens to see if it has issues you want ot don't want. SOme lens shoot softer or harder than others, and finding out before you spend big bux is preferable.

Stefographer,

Here's a review of this lens, principally measured against the Canon EOS 24-70mm f/2.8L and the Tamron SP 28-75mm F/2.8 XR Di lenses:
www.the-digital-picture.com/Revi....aspx

Good luck!

Blessings and Light,
M

I've got a 50mm Sigma macro lens. I chose it because of the reviews I read however it has never lived up to my expectations because the focus is never quite right. The lenes is a couple stops slower than the Nikkor niffty fifty but still it should not hunt so much on AF given a D200 or D300.