KENKO 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 are designed to match the optical quality of the prime and telephoto zoom lenses (even at the edges). The optical design of the elements and light path is wide enough not to cause vignetting.
The PRO 300 family are designed to work best with telephoto zoom lenses of 100mm and above. 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 at under 50mm.
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*.
Full AF operation with PRO 300 2.0x is possible when using camera lenses with maximum 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. (Manual focusing is required when using lenses with smaller maximum f-stop value than those given above.)
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.
Kenko’s Teleplus DGX teleconverters are available in Canon and Nikon fittings. When using a DGX converter with a digital SLR camera, the converter automatically determines the resulting focal length and aperture of the combination and records this in the image file’s EXIF data.
* Most Canon EOS camera bodies are programmed to shut down their auto focus if the calculated effective aperture for the lens and teleconverter is smaller than F5.6, the Kenko Teleplus PRO 300 converters work the same way.