I'm learning photography and all its elements. Probably this question is really stupid, but I have to ask.
I'm not dealing well when the question is equipment and one of the reasons I know this is because of the negative comments in my answer:
When I asked that question, I didn't know these lenses are for different purposes. In fact, I still don't know. To me, they all look like telephoto and I can take the same kind of pictures with them: birds, surfing, etc.
All I know about lens categories I learned here: http://www.usa.canon.com/cusa/consumer/products/cameras/ef_lens_lineup
But I don't understand several things, like:
How can a EF 17-40mm f/4L USM be an "Ultra-Wide Zoom" and the EF-S 18-55mm f/3.5-5.6 IS be a "Standard Zoom"? One starts with 17mm and the other one with 18mm, they look the same! In my mind, a wide angle lens should start, at least, with 10mm.
How can a EF 50mm f/1.8 II be "Standard & Medium Telephoto" and EF 50mm f/2.5 Compact Macro be "Macro"? They have the same focal length!
Here's what I think is true at the moment: A lens has two important aspects: focal length and aperture. That's all I have to care about. Of course it's not correct, that's why I want some advice to get in the right way of thinking when I buy my next lens. So, what can I read to make the right differentiation between them? How can I know which lens is better for my purposes?
OBS: I'm a fan of the chosen answer in this question: How to choose a lens for my first DSLR? I love to keep things simple and I don't care too much about technical details. It can seem like paradoxical stuff because of this question, but it's not. I'm asking this because I want to buy the right lenses without wasting money, but in the simplest way.