The Kenko Teleplus Pro 300 DGX converter provides a 3.0 magnification for Canon lenses. The elements are made of multi-coated optical glass supplied by the Hoya Corporation, designed to match the optical quality of Canon brand telephoto zoom and prime lenses, even at the edges. The optical design of the elements and light path are wide enough to prevent vignetting.The Pro 300 converters are designed to work best with prime lenses over 50mm, and with telephoto lenses ranging between 100 - 500mm. Communication and signal integrity between the body and lens is maintained with Kenko’s Gate Array IC (Integrated Circuitry) technology. Due to the three stop loss, the Kenko Teleplus Pro 300 DGX 3.0 does not feature AF capability, and will require manual focusing.