Sigma Lens Compatibility

[Kantankerous]

This may sound like a stupid question guys but how do you tell whether or not third party lens brands such as Sigma or Tamron produce certain products that are compatible with your camera? I keep seeing Canon EIAX for the Sigma 17-70mm F2.8-4 DC Macro OS HSM and I'm not sure what that means. I'm using a relatively old camera body in the Canon EOS 20D. Can anyone help clarify?

Also having said that, I am thinking of getting that lens (provided it's compatible of course) so it'd be great if you could help me in terms of what sort of price I should be paying for a new one and what its greatest features are. At the moment I'm looking for an improvement on the stock 18 - 55mm that came with my camera and I'm hoping this will provide me with a good well rounded lens that I can take anywhere.

Any help would be great! Cheers.

[RLucas]

Have you looked at the lens chart on Sigma's site? The HSM stands for Hyper Sonic Motor. The focus drive is built in for use on bodies that don't have a built in focus motor.
Here is the link.

Sigma - Lenses - Lens Chart

Here is a link that will tell you what all those crazy abbreviations mean!
Sigma - Lenses - Overview

[Kantankerous]

Ahh that clarifies things a lot more though I should've checked on their website first.

Appreciate the help!