ENKO Teleplus Pro 300 converters are made with precision quality multicoated optical glass supplied by Hoya Corporation, the worlds largest manufacturer of optical glass. These glass elements were designed to match the optical quality of the prime lens (even at the edges) and telephoto zoom lenses. The optical design of the elements and light path is wide enough not to cause vignetting.

The PRO 300 family are designed specifically to be used with prime telephoto lenses of 100mm or above, such as the Tokina AT-X 300 AF PRO, 300 mm f/2.8 lens, and work best with telephoto lenses of 200mm to 500mm. The PRO 300 can be used with telephoto zoom lenses as well as prime lenses. However, Kenko does not recommend them for zoom lenses that have a range starting under 50 mm.

KENKO PRO 300 AF Teleplus converters have genuine Gate Array IC (Integrated Circuitry). It means that the converter's own unique circuitry maintains signal integrity between the camera body and lens. These converters are 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. The same light and contrast requirements apply.

The Kenko 1.4x Teleplus Pro 300 DG converter has genuine Gate Array IC (Integrated Circuitry). It means that the converter's own unique circuitry maintains signal integrity between the digital or photo camera body and lens. These converters are designed to electronically operate the same way as an original manufacturer's converter.

The 1.4x teleconverter (also known as a tele-extender) will multiply the focal length of the existing lens by 1.4x, and will cut back the amount of light by one f/stop. For example, using a 1.4x teleconverter with a 300mm lens will effectively increase the focal length to approximately 420mm. A lens set to f/2.8 will now be f/4.

Teleconverters are best used with longer telephoto lenses and are not recommended for lenses wider than 50mm, e.g. 28-105mm. However, full AF operation is only possible with lenses with open aperture of f/4 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. Manual focusing is recommended when using lenses with smaller open f-stop value than those given above.