A lens accessory that fits between the lens and the camera body. It extends the focal reach of the lens - often by a factor of 1.4x or 2x. So a 200mm lens with a 1.4x TC suddenly becomes a 280mm lens. You can think of the TC working by magnifying the image at the centre of the frame.
Unfortunately, teleconverters have two drawbacks. First, they reduce light entering the camera by a stop or two, which often prevents a cameras autofocus system from working if the resultant widest aperture is greater than around f/5.6 or so. And second they reduce the image quality. High quality converters coupled to high quality lenses still yield excellent results, but if you have an inexpensive consumer lens dont hope to be able to slap a teleconverter onto it and get acceptably non-blurry results. Sadly life doesnt work that way.
cf. focal length.
Entry last updated 2002-04-11. Term 1212 of 1487.
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