cheineck wrote:
I use a Tamron 1.4 teleconverter on my Tamron 70-300 on my Canon 5D Mark II... it works great! Just a little loner to auto-focus than without the teleconverter. It's a wonderful lens and teleconverter.
From Kenko's website:
"The PRO 300 family are designed specifically to be used with prime telephoto lenses of 100mm or above, such as 300 mm f/2.8 lenses, 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 converterÄôs 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 manufacturerÄôs converter.1
Full AF operation with PRO 300 2.0x DGX 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 cameraÄôs 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, DGX full AF operation is possible with camera lenses having a maximum aperture of F4 or brighter. The same light and contrast requirements apply.
The DGX Teleplus converters have updated circuitry to record exif data more accurately. In the exif exposure data (meta-data recorded with a digital picture) DGX converters record the equivalent aperture and focal length of the lens setting plus tele-converter. Optically and mechanically they are the identical to the prior high-quality DG series converters.
Most Canon EOS camera bodies are programmed to shut down auto focus if the calculated effective aperture for the lens and teleconverter is smaller than f/5.6, the Kenko Teleplus PRO 300 converters work the same way.
Important Note:The Kenko DGX TelePlus converters are not compatible with the Canon Digital Rebel XT / EOS 350D camera body and will not function on them. All other Canon DSLR cameras bodies work with Kenko DGX converters.
Specifications 1.4X 2.0X
Model: PRO 300 AF DGX 1.4X PRO 300 AF DGX 2.0X
Magnification: 1.4x 2.0x
Depth of field: 1/1.4 of prime lens 1/2 of prime lens
Minimum focus distance: Same as prime lens Same as prime lens
Construction: 5E / 4G 7E / 4G
Diaphragm coupling: Fully automatic Fully automatic
Lens coating: Digital Multi Coating Digital Multi Coating
Exposure magnification: Approx 2 times (equivalent to 1 diaphragm) Approx 4 times (equivalent to 2 diaphragm)
Barrel length: 27.0mm approx. 51.0mm approx.
Weight: 4.6 oz.(132g) 6.4 oz.(184g)
Mount Available for: Canon-EOS* / Nikon-AF Canon-EOS* / Nikon-AF
*Canon EF-S lenses are not applicable. "