Kenko TelePlus MC4 AF 2.0X DGX Teleconverter The Kenko TelePlus MC4 AF 2.0X DGX Teleconverter (also known as a tele-extender) gives you the dramatic effect of doubling the focal length of your lens by 2x, and will cut back the amount of light by 4x (2 f/stops). The MC4 features a 4-element, 4-group design with multi-coated lens elements, and fully automatic diaphragm coupling. With the Kenko TelePlus MC4 DGX your prime lens' depth of field is reduced by 1/2, but retains the prime minimum focusing distance. Using a 2x teleconverter with a 300mm lens will effectively increase the focal length to 600mm. A lens set to f/2.8 will now be f/5.6. The MC4 AF 2.0X DGX converter has genuine Gated Array IC (Integrated Circuitry). This means that not only the converter's own unique data but all data sent from the camera body provides full exposure metering and linkage for electronic flash photography. This converter is new. Never used, only removed from box to inspect and photograph Specs Mount Canon EOS Magnification 2x Optical Design 4 Elements in 4 Groups Length 1.02" / 26 mm Weight 3.9 oz / 111.0 g