Glass elements were designed to match the optical quality of the prime lens (even at the edges) and telephoto zoom lenses
Optical design of the elements and light path is wide enough not to cause vignetting
Designed specifically to be used with prime telephoto lenses of 100mm or above
Work best with telephoto lenses of 200mm to 500mm
Can be used with telephoto zoom lenses as well as prime lenses
Kenko does not recommend them for zoom lenses that have a range starting under 50 mm
Genuine Gate Array IC (Integrated Circuitry) - converter's own unique circuitry maintains signal integrity between the camera body and lens
Designed to electronically operate the same way as an original manufacturer's converter
With the PRO 300 1.4x, full AF operation is possible with camera lenses having a maximum aperture of F4 or brighter (same light and contrast requirements apply)