Tele converters for most 35 mm and roll-film cameras fit between the camera body and the ordinary lens, and increase the magnification at any given focus setting. They do this by magnifying the central portion of the image, and so can emphasise distortion or poor definition. They are available in various strengths, inclusing 1.4×, 1.5×, 2×, 2.5× and 3×. All tele converters cause a loss in light (for example 1 stop for a 1.4× model and 2 stops for a 2× model) but TTL exposure compensates for this. The first models on the market produced poor quality images, but modern ones give good results. Some tele converters are designed for use with specific lenses. A macro lens that can provide magnifications up to 1:2 on its own will produce magnifications up to 1:1 with a 2× converter.
Digital cameras and 35 mm cameras with fixed lenses use tele converters that screw into the filter mount. On most digital cameras, the LED screen must be used to compose pictures when a tele converter is fitted, because the converter does not affect the image seen through the viewfinder.
See also: Macro converters