I am trying to learn more about what I see and what things mean when reading up on choosing a certain lens for my camera. I look up a lens like this one;

http://www.canon.ca/digitalphotograp...?id=961&cid=12

And I can understand and interpret all of the specification information aside from lens construction. I don't know and would like to know (if someone would be so kind to educate me) what this is, what to look for, what significance it has when buying a lens, and just generally anything else that you know about the topic :P sorry if that's a bit general, I'm a bit of a moron when it comes to mathematical values (ironically I choose the art which is centered around manipulating those mathematical values to get pictures! :idea: )so when I see something like " 17 elements in 12 groups " I go