Digital single-lens reflex cameras offer more flexibility to the photographer by allowing him to change the lens on the camera to suit the different settings pictures may be taken in. Digital camera lenses are similar to film camera lenses except for compatibility issues. You should also consider the aperture, zoom type, focal length, and focusing type of the lens before buying.
Compatibility
When looking for a digital camera lens, make sure the lens is compatible with the digital camera body you will be using. Even if the lens fits the camera, it may not work with the digital elements. This is especially true if you are purchasing a third-party lens.
Aperture
Aperture refers to the maximum amount of light a lens can let in when taking a picture. Fast lenses, those with an aperture of 2.8 or less, are useful for freezing high speed action like sports.
Focal Type
Camera lenses can be either fixed focal length lenses or zoom lenses. Zoom lenses cover multiple focal lengths which allows the photographer to change the composition of the photo without moving. Fixed focal length lenses, also known as primes, are stuck at one focal length, but primes usually take slightly sharper pictures than zooms.
Focal Length
The focal length needed is dependent on what the camera will be taking pictures of. If the subjects will be close, small focal length, between thirty and sixty millimeters is sufficient. If you need to zoom in close, a larger focal length of one hundred or more millimeters may be better.
Focusing Type
Most lenses have the mutually exclusive manual and auto focus options, meaning when the lens is set to auto focus, you cannot change the focus manually without risking damage to the lens. Some lenses have full-time manual focus, a feature that allows the focus to be tweaked manually when in auto mode.
Tags: focal length, auto focus, camera lenses, focal length, focal length lenses