The Kenko TELEPLUS HD DGX 2.0 teleconverter contains a set of optics which multiply the focal length of your prime lens by 2x, turning a 300mm lens into the equivalent of 600mm. Teleplus HD DGX converters use unique circuitry which maintains signal integrity between the camera body and lens. It also allows accurate recording of digital EXIF data. Multi-coated optical glass is used in the optics, which is supplied by Hoya Corporation, the world's largest manufacturer of optical glass. Full AF operation with the HD DGX 2.0x is possible using a camera lens with an open aperture of F2.8 or brighter. Please be aware that AF will work properly only if there is enough light and contrast on the subject to activate the camera's AF sensors properly, otherwise manual focussing may be necessary.