Camera lenses are usually made of several optical lenses.
Camera lenses work in much the same way as the human eye, focusing an image and transmitting light, color and shape to the camera itself. Lenses are usually made from optical glass, but may also be made from plastic. The important thing is that they focus light rays. It took a long time for the camera lens to develop from its simplest form to the type used in modern cameras.
Types
Most "point-and-shoot" cameras use a general-purpose lens with a standard focal length designed to mimic the way the human eye sees an image. This isn't the only type of camera lens, though. Special-purpose lenses are often used with advanced cameras. For instance, the telephoto lens is designed to make distant images come closer, and works much like a telescope. Panoramic lenses can take wider pictures, and are useful for scenery, while fish-eye lenses enlarge the central part of the image, compressing details on the edges. Many cameras also have a zoom lens, which can be used to get a closer view of a distant subject.
History
The modern camera lens was developed from other optical lenses used for magnifying and vision correction. Before the development of these lenses, the only type of camera available was the camera obscura, or pinhole camera, which made a fuzzy image that worked only in dark rooms. By the 16th century, the telescope lens had been developed, making possible the camera lucida--a type of projector. In 1611, Johannes Kepler described single and compound lenses and experimented with grouped lenses. The fast aperture portrait lens was developed in 1841, and by the early part of the 20th century, fast, sharp camera lenses were developed. Modern camera lenses are still very similar to these.
Technology
Lens-coating technology has made higher-quality camera lenses possible. Coated lenses mean less reflection and better light transmission. The addition of computer calculation now allows much more precise lens-making, as well. Modern camera lenses may still be essentially the same as earlier ones--a curved surface with a specific focal point--but that focal point is now much more precisely calculated.
Production
Modern camera lenses begin with a design, chosen based on the type of photographer the lens will be marketed to. Many camera lenses are actually made up of many individual glass lenses, each chosen for the way it bends and focuses light. These individual optical lenses are called lens elements, and make up the camera lens itself. They may be made of different types of glass and have different coatings. After the design comes prototyping, where a version of the camera lens is made and tested under all kinds of temperatures and conditions. If the prototype passes these tests, it can be put into mass production.
Considerations
Historically, photographers have needed to pay attention to the type of lens they use and the way it is adjusted. With the development of auto-focus lens sets for modern point-and-shoot cameras, it's easy to avoid thinking about the way a camera works. These cameras don't provide the control of a SLR (single lens reflex) camera, though. Serious photographers may wish to invest in a variety of different lenses and a camera of this type to get the most out of their pictures.
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