It's a 70-200 f/2.8L. I paid $1000 for a used one, about ten years ago. For digital SLRs, there is no digital zoom - it's all optical. But there is a "digital conversion factor" because the digital sensor is smaller than a 35mm film frame that the lens system was originally designed for. The Canon 400D/XTi has a 1.6x conversion factor. That makes the 70-200 lens comparable to a 112-320mm on a 35mm camera. It's not exactly the same, but the reach and framing are the same.

You might want to take a look at some of the stuff in our Learn section, especially the digital SLR guide. You already have a camera, but there's probably some useful information in the guide, anyway. I know there's some stuff about the crop factor: [url=http://www.photographyreview.com/digitalslrguidecrx.aspxDigital SLR Guide >>[/url]

Hope you're enjoying the site. I like seeing enthusiastic new converts. Where in California are you? There are pretty good groups of members in the Bay Area and in LA.