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01-21-2012, 02:26 AM   #1
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Kenko AF 2X Teleplus Teleconverter 7 Elements MC7

Will this work with the Sigma APO 70-200 f2.8 EX DG SO HSM

I have herd that it has trouble focusing in bad ligh (but how bad is bad)

I want to extent my range for sport and bird.

any sugestions?

01-21-2012, 11:05 AM   #2
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Your zoom lens will have an effective aperture of f/5.6 with the teleconverter. This is getting into difficult AF territory. You will need good light and/or high contrast edges to focus with. You can help the system a bit by using the centre point setting for the AF. You also lose shutter speeds. If you are working at 200mm at ISO 200, and without converter you have a shutter speed of 1/500, with the converter your shutter speed will become 1/125 while your focal length has increased to 400. This is hitting the limits of the shake reduction as well, so I recommend a good tripod for the combination. I use a teleconverter with my 400mm lens, but find that f/8 is really difficult to work with at the best wildlife times of day, dawn and dusk.

The only way you can find out if it will work for you is to try it. What I would suggest is to take the same scene with and without the converter. It is possible that cropping the image will give you the same quality of final image.
01-21-2012, 02:30 PM   #3
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I just bought the same today but with Tamron name on it. I Tested on my Sigma 17-70, work perfectly . Then I try it on my Sigma 50-500, and yes it got problem to focus properly , But I expected that. But I can focus manualy
06-18-2012, 05:30 PM   #4
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QuoteOriginally posted by bobmaxja Quote
But I can focus manualy
Using your (anyone's!) MC7 teleconveter can you freely turn the focus on an auto-focus lens (with the camera set to MF/Manual-Focus)?

I ask as I just picked a used MC7 up and am having trouble physically manually focusing with it attached. With the camera switched to manual focus I can't easily turn the focus ring on the lens, and it's very 'jerky' when/if it does "give"! Certainly not smoothly enough to actually focus on anything.

Is this typical/normal for the MC7 (used with auto-focus lenses), or is there an issue with my MC7 copy?

FWIW I'm initially pleased with the image quality (vs cropping), and it does auto-focus if given good enough lighting and contrast, but the inability to manual focus (auto-focus lenses) makes it rather unusable for most circumstances.

Hopefully I'm missing something, as the vendor doesn't have another to replace it with. :-(

Thanks for any insights!

Last edited by Cedar; 06-18-2012 at 10:37 PM.

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