[race_ray]

Any recommandation for 2x extender used on 70-200 mm 2.8 lIS

[race_ray]

2x or 1.4x batter

[pongyee]

All EOS cameras except the EOS 1v and EOS 3 will shut down AF with a lens-converter combo which is slower than f/5.6. However, this is not entirely true. Third-party TCs do not transmit the correct aperture - e.g. a f/4 lens + generic 2x converter looks still like a f/4 lens for the camera while the Canon EF 2x will calculate and transmit the correct f/8. So what happens ? You'll indeed have a "sort of AF" till f/8 or so but don't expect arrucate and stable focusing. On a sunny day you'll probably get a reasonable focus performance up to f/6.7.

BTW, there is a possibility to make AF working with a slow combination of lens and Canon converters. Canon converters have 3 additional contacts (I think) so simply use a piece of thin plastic tape to block them. With this trick it should be possible to get AF on combos like 500/4.5+1.4x or 180/3.5+2x.

Do not try not use a tele converter on "low-performance" lenses like slow 75-300mm zooms. The resulting image quality is just "poor".

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以上的文章節錄自：
http://www.photozone.de/8Reviews/canonFAQ.htm#3Q5a

[race_ray]

so................pongyeee hing, which one you recomand for my small white?