I have purchased recently a Kenko 2X - MC7 converter, and the result of the AF has been:

2X + EF 28-135/3.5-5.6 = AF at any of the 45 focus points. 2X + EF 100-300/5.6L = AF at any of the 45 focus points.

In both cases, using a circular polarizer (2 stops less) and at 19:00 hours and cloudy day (very low light). This means that the EOS is able to AF even at f/11 (- 2 stops of polarizer..f/22 !!) and not only in the center point, in all of the 45 points...

Isn't it amazing?

Thanks to everyone for your previous advices-answers: My hama polarizer is not valid for the 100-300/5.6L lens (mistery... because all other brands work perfectly: Soligor, B+W...). And about the kenko 2X, you already now the result reading above!

Peio Ezkurra - Basque Country.

-- Peio Ezkurra (peio_e@hotmail.com), February 18, 2002

Answers

I'm not surprised that the EOS 3 will AF one stop less than what Canon says. The same is true of most other Canon bodies. My EOS Elan and Elan II will AF with an f/5.6 lens and a 1.5x T/C.

However it doesn't do it reliably or quickly or without hunting back & forth sometimes. But I can get it to work.

The real question is, How good is the optical quality with the T/C? I have to deperatly want more magnification to use a T/C with my tele- zoom. But your 100-300 f/5.6L does have better image quality to begin with, so maybe it's still acceptable. I'd like to know if it is.

-- Jim Strutz (j.strutz@gci.net), February 18, 2002.

Any zoom with a TC is a compromise. I was recently looking at some of my father's pictures from his recent trip to South Africa, which he took with a 100-400L IS + 1.4X TC (Using an EOS 1V). Some of them were truly stunning, whilst some seemed a little soft. Stopping down a little (from F8 down to F11 or so) seemed to help a lot.

However, the 100-400L IS is a very different lens to a consumer zoom. There are very few zoom lenses under $1000 which I'd consider putting a TC on (the 70-200 F4L is one). Depends what you consider acceptable though.

-- Isaac Sibson (isibson@hotmail.com), February 18, 2002.

Jim, I use Canon's 2X teleconverter with my 70-200 2.8L and with my 300 2.8LIS and the results are very very impressive. All the best shots have been taken with the lens mounted to my tripod, but even then I have had great results with the resulting 600 5.6 panning wildlife. I have never used any 3rd party teleconverters to offer a comparison opinion. It does seem that many 3rd party converters work with the shorter lenses, not sure why that would be, and Canon's does not.

-- Robert DiTommaso (newbabyd@yahoo.com), February 19, 2002.