Does anyone have a site that I can go to in order to learn and read up on the different kinds of lens that you can buy and what they all do as far as function/models. I need something that is going to explain what an APO is, what a G lens is and so forth. There has to be something out there that gives a break down of lens with a description. I know what lens are considered telephoto, macro etc. But there are different kinds of those types and I don't know what they mean. I've done search after search and can only come up with what is considered a macro, telephoto, wide angle etc. That's not what I'm looking for. Hopefully that makes sense.