lukeybaby said:what does "mm" mean in a manual camera?? eg: 28-90mm lens?? and what does the this mean f/4-5.6 lens??? is that how much light it lets in?? sorry about all the Q's, im pretty new to manual photography.
p.s-do you know of a good site which can inform me more of different parts on a manual cam, etc?
"mm" means millimeters, and is a measure of the focal length of a lens. Your example of a 28-90mm lens is one that zooms from a wide angle of 28mm out to a telephoto 90mm. The term "f/4-5.6" refers to the maximum aperture of the lens. In this case, this lens can open up to f/4 at 28mm, and to f/5.6 at 90mm.
The lower the f-stop number, the wider the lnes can open, and therefore the more light that can strike the film. f/4 is wider than f/5.6, and so you can use faster shutter speeds.
There are many web sites that talk about camera basics. The only one I can think of off the top of my head is Silverlight Photography Tutorials,
Hope this helps.