Nikon Teleconverter Camera Lenses
Sometimes known as a tele extender lens, a Nikon teleconverter camera lens enables you to increase the focal length of a lens to produce a telephoto effect. It is a magnifying lens that is popular with nature and wildlife photographers so that they can extend the photographic reach. Nikon's range of AF-S teleconverter lenses offer 1.4x, 1.7x and 2x magnifications.
How does it work?
A teleconverter lens is a secondary lens that sits between the camera and the photographic lens. It is used to enlarge an image by an objective lens. A group of lenses work as a single diverging lens that produces a virtual object image which, when focused at a distance, increases the size of the image. If the teleconverter lens is slower than a standard lens, it could reduce the aperture to the point that the camera's autofocus function will no longer be effective.
A different type of teleconverter lens, called a teleside converter, is secured on the front of the camera's standard lens instead of between the camera and photographic lens. These afocal lenses won't decrease brightness but they may increase image aberrations.
Disadvantages of using a teleconverter lens
A Nikon teleconverter camera lens is much smaller in size than a standard zoom lens but there is a loss of sharpness, lens speed and sometimes light. They work well with Nikon and Canon camera lenses including the range of Nikon macro lenses. However, because most lenses have not been designed to work with other lenses, there can be incompatibility issues with some cameras.
Wide angle and zoom lenses are not compatible with teleconverter lenses. Zoom lenses are slower and therefore get less light in order for the camera's autofocus to work. As the teleconverter lens may reduce the aperture quite significantly, this will have an impact on accuracy and speed.
As there are more lens parts involved, when you zoom in on a subject there may be some lens decentering where one or more of the optical elements may move or tile from the principal lens axis. This will lead to blurring or distortion of the image.
Unless you are using a tripod with a teleconverter lens, when you extend the focal length any movement of the camera may become more apparent. The focusing speed reduces with the use of teleconverter lenses, sometimes to the point where the camera's autofocus function will not work.