Tell me something about the optics of a SLR camera?

Question

What do the terms wide angle and 13-45mm written on the camera lenses mean?

Answer 1

I'm answering this assuming you are meaning a SLR film camera, as the optics are different for digital SLRs, and usually only professional photographers or advanced amateurs have one of those.

A 50 or 55 mm lens is considered a "normal" lens. Pictures taken with that lens will look about like the scene does when you look at it live, in person.

Lenses with bigger numbers are "telephoto" lenses. They make distant things look closer by showing you a smaller angle of view. Imagine looking at something through binoculars.

Lenses with smaller numbers are "wide angle" which means they show a lot more stuff to the side and make things look a little further away. Wide angle lenses are good to take pictures indoors, where you can't get far enough away from your subject with a normal lens. An extreme wide-angle lens (a "fish-eye" lens) greatly distorts the picture. Things that are closer to the camera will look larger.

"13-45" indicates a zoom lens. It can be set to any length from 13 mm to 45 mm... a fairly strong wide angle to a near-normal lens.

Answer 2

Wide angle simply means that the lens is viewing a wider area that the human eye normally sees.

For a 35mm camera, a "normal" lens, that is a lens that approximates what the human eye can see has a focal length of approximately 50mm, hence it is called a 50mm lens. Any focal length less that 50mm would then be a wide angle lens.

(A telephoto lens is any lens that has a focal length greater than 50mm.)

A lens that says 13-45mm is called a zoom lens. It has a varrying focal length that can be adjusted from 13mm (super wide angle) to 45mm (minimal wide angle).

Answer 3

A normal focus lens is a 50mm lens. A lens with a smaller number, such as 13-45mm would be a zoom lens that had a wider field of view than the standarf 50mm lens.