Lens

Digital camera lenses come in two categories; there are SLR interchangeable lens and “adaptor” lenses. Adaptor lenses are frequently used on point and shoot cameras, but are also available for SLR lenses. SLR lenses come in many different shapes and sizes that cover a wide range of focal lengths, and different camera brands such as Canon or Nikon have their own unique lens mounts on DSLRs that allow them to accept only compatible lenses. Adaptor lenses are usually screw-on lenses that require an adaptor before you can mount them to your digital point and shoot (make sure your camera has adaptor threads) or SLR lens. These adaptor lens cannot zoom and usually come in two varieties: wide-adaptor and tele-adaptor.

There are two categories of SLR lenses; prime lenses and zoom lenses. A prime lens offers a single focal length only, such as 50mm, or 85mm. A zoom lens offers a range of focal lengths, such as 17-40, or 18-55.

Prime lenses differ from their zoom lens counterparts in that they offer only a single focal length. There is no ability to adjust the image ‘zoom’ with the lens, and the photographer must move the camera if the shot needs to be taken closer. Prime lenses are often used because they frequently offer the ability to lower f-stop numbers (therefore allowing them to be used in less light). Prime lenses are frequently cheaper, and typically offer better image quality than a zoom lens. A zoom lens requires many sets of elements to provide a proper image, while a zoom lens is only designed to shoot at one focal length. Prime lenses are frequently used at sporting events, or for indoor shots where low light is an issue. Prime lenses are also typically much lighter than their zoom counterparts, and much shorter. A 50mm prime lens is typically less than two inches in length.

Zoom lenses offer much greater flexibility for the photographer as they can cover a variety of subjects and it is possible to get “all in one” lenses. It is therefore possible to cover multiple situations without changing lenses, such as for street photography or vacation photography. This can be used to great advantage in dusty environments where changing lenses would introduce dust into the camera body. On lower end zoom lenses, the exposed zooming element may introduce dust into the lens itself however. Higher end zoom lenses often zoom internally, with no visible moving parts on the exterior of the lens.

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