Camera Parts: Zoom Lens
One of the most important camera parts is the lens. The earliest cameras had "fixed" or "prime" lenses. These lenses capture images and project them onto a sensor or film plane in the back of the camera from a single spot. However, technical experts allowed photographers more flexibility when they invented the zoom lens.
Pros and Cons of a Zoom Lens
Essentially, what the zoom lens does, is it changes the focal length of a lens by manipulating various lenses within the longer zoom lens, housing to change the camera's focal length. What this means is that you can bring objects before the lens in focus from various different distances from the camera. This convenience lets a photographer take a focused picture of an object five feet away or 100 feet away without moving. They do this by keeping several lenses that move closer-together or further-apart within a housing.
The negative aspect of this kind of lens is that, for every separate lens, or "element," a little bit of light is lost. Consequently, as the amount of light that makes it to the sensor or film is what impacts the quality of the final image, the photographer is limited in either quality or potential (especially as far as low-light circumstances). A sharper image can generally be captured with a prime lens, but the convenience of a zoom lens may be worth that sacrifice.