Types of Camera Lenses
by Denise Gormish (Mar 6, 2007)
Purchasing a Single Lens Reflex (SLR) camera gives the photographer the advantage of choosing among different lenses and the ability to change those lenses. The choices seem endless, though, and it is sometimes difficult to determine which additional lenses to buy.
Here's a run-down of the most common lenses and some of the specialty lenses for an SLR camera.
The three basic lens types, determined by the focal length (measured in millimeters) of the lenses, are the following:
Lenses come in either prime or zoom. Prime lenses have a fixed focal length. In order to fit more or less into the viewfinder, the photographer must physically move forward or backward. Focal length in a zoom lens can be changed by turning the zoom ring on the lens. A zoom will have a variable focal length such as 28mm-105mm. While zoom lenses are more convenient for storage and versatility, prime lenses often have a sharper lens and work better in low-light situations.
In addition to focal length, consider the lens speed and its focusing distance. The lens speed is determined by the f-stop setting. A faster lens will be heavier and more expensive. The focusing distance is the distance from the lens to the subject needed to achieve a focused photograph.
Other special lenses to consider include the following:
Digital camera SLR users need to be aware of the focal length differences in lenses that are interchangeable for film and digital cameras. All focal lengths listed on interchangeable lenses are for film cameras. To get the true focal length of a digital camera the number needs to be multiplied by 1.6. Remember that the lens won't be as wide on a digital camera as you would get on a film camera using the same lens. For example, the standard 50mm lens on a film camera is actually 80mm on a digital camera.
When purchasing a new lens, first consider your needs. What will you be photographing? The subjects of your photographs should dictate whether you need a normal, telephoto or wide lens. Then, consider the trade-off between the optics quality, the camera's weight, the convenience of a prime vs. a zoom lens, lens speed, focal distance and price. Often it will be a balance of these considerations that leads you to a good camera.