Zoom

A Zoom lens is one that can vary its focal length. The photographer can stand in one place and zoom in tight, or zoom out wide. With a fixed lens, the photographer must change the distance he stands from the model to accomplish the same thing.

Telephoto Zoom

The zoom range can be from a short telephoto lens to a long telephoto. Generally a large difference in the focal lengths will result in some quality loss, or much higher expenses. Since the f-stop is the ratio of the focal length to diameter of the aperture, the fastest f-stop will be at the lowest focal length, and increasing the zoom by increasing the focal length, for the same diameter opening will result in a larger f-stop (less light).

Wide Angle Zoom

The zoom range covers from a very wide angle to slightly wider than normal field of views. Generally, the shorter focal length at the widest field of view with either suffer quality, distortion, vignetting (dark corners), or increase the price considerably.

Standard Zoom

The zoom range crosses through wide angle to telephoto. Generally these are not extreme wide angles, nor extreme telephotos.

Fixed versus Zoom

A non-zoom lens is referred to as a prime lens. In days of yore, prime lens were considerably sharper than zoom lens. While most primes still have an upper hand in quality, the differences in a quality zoom and a fixed focal length may be small. Some photographers carry around several different fixed focal length lens, while other photographers carry around one zoom lens. The convenience sometimes literally and figuratively outweighs the other.

Comparisons with Point and Shoot Cameras

Many small pocket point and shoot cameras refer to their zoom lens as 3X or 5X or 12X. The "X" refers to the shortest focal length of the zoom lens. A camera with a 4X zoom lens might not have more telephoto power than another camera's 3X lens. If the 4X camera has a 24mm equivalent wide angle focal length, its equivalent telephoto focal length is 96mm. However, a 3X camera that has a 35mm wide angle will reach out slightly further to 105mm at its maximum focal length. When comparing zoom lens, always refer to the optical zoom range, not the digital zoom.

Digital Zoom

Digital zoom is nothing more than cropping the image. Many photographers disable their digital zoom feature, and prefer to crop back at their computer when necessary. A digital zoom has its purposes, perhaps in voyeurism as an example to allow the photographer to see his subject better before and during the photo taking.