Digital Camera Lenses

There are several types of digital camera lenses and terminology associated with them. The focal lengths of lenses are described in terms of 35mm equivalent.

Fixed focal length lens
The camera lens does not change at all. With a fixed focal lens the only way you can get a close up is to move closer to your subject. But don’t get too close ot your subject’s features are likely to become distorted.

Types of zoom Lenses
Just because your camera is digital doesn’t mean your zoom lens should be!

Optical zoom lens
An optical zoom is a true zoom. Its focal length changes and the zoom mechanism itself extends and retracts so an image is magnified by the lens itself. An optical zoom produces the best quality images.

Digital zoom lens
A digital zoom is not a true zoom. It is a simulated zoom that enlarges the central portion of an image in the camera. The actual length of the lens does not change. Digital zoom produce images with reduced visual quality.
Interchangeable and converter lenses

Single Lens Reflex digital (dSLR) cameras accept a wide range of interchangeable lenses. Some lenses used with a 35mm film SLR may be compatible with the same brand dSLR, though features such as auto-focus may not work if the lens in old. You can get decent consumer level lenses for reasonable prices, however high quality professional lens can cost $1000 or more.

Add-on converter lenses are available for many compact digital cameras. Converter lens are relatively inexpensive and extend the flexibility and capability of a built-in lens.

source:digicamhelp.com