The Kenko Teleplus MC 7 AF converter has the effect of doubling the focal length of your lens. For example, using the MC 7 AF teleconverter with a 300 mm lens will effectively increase the focal length to 600 mm. Placed between the camera body and lens, a teleconverter contains a set of optics that will effectively increase the focal length of any lens it is used with. The Kenko Teleplus MC 7 AF converter has the effect of doubling the focal length of your lens. For example, using the MC 7 AF teleconverter with a 300 mm lens will effectively increase the focal length to 600 mm.