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Old Feb 5, 2008, 2:32 PM   #1
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Does anyone have a generic1.4X Teleconverter that reports the corrected aperture and focal length to the camera?

I have a KM5D and a Sigma 75-200/2.8-3.5. The lens won't autofocus oradjust aperture when mounted directly on the camera, but if I insert a Quantaray 2X teleconverter, the lens will autofocus out to about 300mm (corrected) when the maximum corrected aperture reaches f/6.3.

I tried an old Kalimar 1.7X TC, but the lens won't autofocus at all, just like when the lens is mounted directly to the camera without a TC.

I understand that the chip in the lens isn't compatible with the KM5D, but the chip in the Quantaray TC is smart enough to work with both thelens and the KM5D. I also understand that many TC's less than 2X don't contain chips at all, and just pass the uncorrected aperture and focal length through to the camera. Therefore, I suspect that the 1.7X TC I have doesn't work because it doesn't contain a chip.

I would like to use this lens with a TC that will permit autofocus. In order to do that, I think I need a 1.4X-1.7X TC that reports the corrected focal length and aperture.

Does anybody know of one?
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Old Feb 5, 2008, 6:12 PM   #2
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The Kenko PRO 300 1.4x teleconverter does NOT correct the focal length or aperture from the Nikon AF-S Zoom Nikkor G VR 70-300 F4.5-5.6G IF ED on a Nikon D70s. Of course it exposes correctly because of the TTL metering! Autofocus and VR work great but there is some purple fringing introduced. See http://forums.steves-digicams.com/fo...793834#p793834 for examples.
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