I want to understand in depth about the lenses ..like 18-200 mm etc, what does this mean?

Question

Is their any website that explains me about this technology?
Please let me know

Answer 1

The website listed below gives a really nice tutorial on that subject.

But basically, a lens with a long focal length is a telephoto lens for distance photography; with a very short focal length it is a wide-angle or macro lens for close-up photography. The "normal" focal length tries to provide about the same angle as the human eye; for 35 mm film that is about 50 mm.

When the specification for a lens says 18-200 mm it means that it is a "zoom" lens that you can vary from a very short to a moderately long focal length.

Answer 2

This might be a good start.

http://en.wikipedia.org/wiki/Lens_%28optics%29

And this one: http://en.wikipedia.org/wiki/Photographic_lens

This is particularly about focal length (i..e. 18-200 mm)

http://en.wikipedia.org/wiki/Photographic_lens#Aperture_and_focal_length

There are many links on the bottom that will take you to different subjects, all related to lenses.

Answer 3

http://www.mtholyoke.edu/~mpeterso/classes/phys301/geomopti/lenses.html
http://en.wikipedia.org/wiki/Focal_length

Search the internet for focal length. Lots of articles out there.

Answer 4

howstuffworks.com