EF 300/4L + 2x Kenko + EOS 3

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I have an EOS 3 body with 80-200/2.8L and 300/4L (and more...). The 80-200/2.8L doesn't permit the Canon original 2x adapter (because of the protrusion in the front), so I'm thinking to buy a KENKO 2x MC7 (the cheap one).

My question is if the AF will work in my EOS 3 with the 300/4L + Kenko 2x MC7. I know that the theorical combination is 600/8 and the center focusing point of the EOS 3 is able to focus with f/8 lenses. I know too that with the original Canon 2x converter, the AF will work, but I'm concerned about the kenko... Anybody with this combination?

Thanks. Peio Ezkurra - Basque Contry.

-- Peio Ezkurra (peio_e@hotmail.com), February 13, 2002

Answers

The problem you're going to have is not that it's too dark, because the EOS 3 can focus to F8 with the central point, but that the Kenko won't report the lens as F8, but rather F4. This will cause the EOS 3 to attempt to use high-precision, cross-type focus, which will not work at F8. It will also give you the option of the other sensors, which will not work correctly either.

-- Isaac Sibson (isibson@hotmail.com), February 13, 2002.

Isaac's right. There are focusing issues to deal with, but the bottom line is, it will work with the center AF point.

-- Jim Strutz (j.strutz@gci.net), February 13, 2002.

It will not change the AF ability but I would recommend you buy the expensive Kenko Pro version of the converter. Or the Tamron, which is the same. Since a third party converter is all you can use on the 80-200, get the best type available. It will help with image quality.

-- Lee (Leemarthakiri@sport.rr.com), February 13, 2002.

Jim-

WILL it work?? I don't know....it will attempt to use cross-type focus, which won't work because of the small aperture, and consequently may end up hunting? I don't think it will switch down to single-axis, because the aperture is believed to be F4, and so it would be like trying to use an F5.6 capable body (EG EOS 5) with an F5.6 lens with a 2X non-canon TC. It will end up hunting like mad....

I think..I don't know for sure... maybe someone with the appropriate bits can try it?

-- Isaac Sibson (isibson@hotmail.com), February 14, 2002.


Hi, I've got the Tamron 2x, EOS 3 and with an f4 lens manually select the centre focusing point it will auto focus just fine. It is quite alarming the way the reduced light changes all the colours through the view finder however the photo's still come out reasonably sharp. Jason

-- Jason Eadie (jason_eadie@hotmail.com), February 14, 2002.


P.S. the Tamron (SPAF)2x reports the correct apperture to the body (ie 2 stops slower). Jason

-- Jason Eadie (jason_eadie@hotmail.com), February 14, 2002.

My question was more about TCs which don't report correct aperture information. Presumably the cross-type AF will not work at F8, otherwise canon would allow it, but the camera will try to use it with a non-reporting TC. With a reporting TC, of course it will work correctly.

-- Isaac Sibson (isibson@hotmail.com), February 15, 2002.

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