The Kenko MC4 2x AF Teleplus is a teleconverter that is placed between the camera body and lens and contains a set of optics that will effectively increase the focal length of any lens it is used with. The Kenko AF Teleplus converter MC4 has genuine Gate Array IC, which means that not only the converters own data, but all data sent from the camera body provide full exposure metering and electronic flash photography.
This computer designed 4-element tele-converter multiplies the focal length of the existing lens by 2x, and cuts back the amount of light by 2 f/stops. Full Auto Focus operation is only possible with lenses with open aperture of f/2.8 or brighter. AF will work properly only if there is enough light and contrast on the subject to activate the camera's AF sensors. Manual focusing is recommended when using lenses with smaller open f-stop value than those given above.
Note! Teleconverters are not recommended for lenses wider than 50mm, e.g. 28-105mm.