Lens Question

[Hill1970]

Canon EF 70-300mm f/4-5.6 IS USM

Can someone explain to me what the letters and numbers mean on a particular lens. What does the EF mean, what does the 70-300mm mean, what does the f/4-5.6 mean, I know that the IS is for image stabilizing, but what does USM mean?

I am just getting started with photograghy and I am trying to figure out the different lenses.

[Snakelover]

Canon = Brand
EF = Electro-Focus (Just means the lens fits the EOS Canon lens mounting system. Lenses that don't say "EF" don't fit the EOS system.)
70-300mm = Focal Range
f/4-5.6 = Largest Aperture for Focal Range (f-stop This is not the whole range of aperatures available, but the range for the lowest f-stop or largest aperture, however you want to look at it, from the smallest to largest focal length of the lens. In this case, the maximum aperature is f/4 at 70mm, but only f/5.6 at 300mm)
IS = Image Stabilization
USM = Ultra Sonic Motor (the type of auto-focusing used)

Other:
EOS = Electro-Optical System (A line of Canon digital SLR cameras)
SLR = Single Lens Reflex (There is only one lens for both picture taking and viewing. In other words, the viewfinder looks through the actual lens so when you look through the viewfinder, you're seeing the exact same thing the sensor "sees.")
Digital = Opening the shutter exposes light to a digital sensor instead of film.

I think I have all that essentially right, although I may have used some technically incorrect terms. If so, someone will come along and correct the weak points. In the meantime, it will get you thinking in the general right direction. Hope it helps.

[Snakelover]

You may also see the letter "L" after the aperture on some lenses. This means the lens is part of the Canon L-Series, their top-of-the-line lenses. It just means they're of the highest quality glass and construction that Canon produces. Some say the "L" stands for "Luxury." I don't know if that's true. Perhaps it stands for "Lighten" as in what it does to your wallet! To me, it just further ensures that the image produced will far exceed my photography skills!

[axisbuck24]

What does the date codes or UX numbers mean on a "L" lens series? Why is it important?

[Kevin]

Datecode on L glass tells you when and where it was made. It's important because you can tell how old the lens is.

[Bluesman]

Sereral models of Canon camera bodies accept both the EF and EF-S lens mounting arrangements.

[bushman]

Also, the L stands for weather resistant on most lenses. I'm pretty sure all but the 100-400 with the push pull design. Smeone please correct me if I'm wrong.