AF or EF Lens

[LUKA]

Can someone explain the difference between an AF and EF lens?
Other newbie questions...

What does the f-stop number mean when describing a lens "70-200 f/2.8"
Is it minimum or max or best?
I bought my camera (Dig Rebel XT) from B&H in New York. The guy who helped me said that for digital cameras, expensive lenses are much less important and that I should look into quality used lenses when buying my next one. This sound right to everyone?
Thanks.

[robertwgross]

Can someone explain the difference between an AF and EF lens?
...
What does the f-stop number mean when describing a lens "70-200 f/2.8"
Is it minimum or max or best?

EF is the Canon designation for the autofocus lenses that fit the EOS line of camera bodies. All EF lenses have autofocus capability. Not all autofocus lenses are EF type.

For some lenses, a zoom focal length range is listed, and then a constant maximum aperture number such as f/2.8. That means at the short end, or the long end, or anywhere in between, you can make the aperture go from f/2.8 to f/22 or f/32 or whatever.

For other lenses, the maximum aperture number varies depending on whether it is the short end or the long end, so you see some numbers like f/2.8-4, or f/4.5-5.6. In nearly every case, the maximum aperture number like f/2.8 is found at the short end.

---Bob Gross---