[lobohuang]

有冇C Hing 用過,效果如何
可否貼o黎看看?

[pongyee]

以下的文章節錄自 http://www.photozone.de/8Reviews/canonFAQ.htm#3Q2c

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On the third-party front there're a couple of cheaper alternatives. Most are junk but there're a couple of serious alternatives that are not all that bad:

Sigma AF 1.4x APO EX
Sigma AF 2.0x APO EX
Kenko AF Pro 300 1.4x
Kenko AF Pro 300 2.0x

The Sigmas can only be used with dedicated Sigma EX lenses plus fix-focal Canon "L-class" lenses with a focal length of min. 135mm & up plus the Canon 70-200L & (probably) 100-400/4.5-5.6L IS. The Kenko Pro converters can be used with all lenses because they do not have a protruding front element (which qualifies this converter to be used on the EF 80-200/2.8L). Nonetheless the Kenko Pro series is optimized for > 200mm tele so the usage with std. zooms is pointless.
As a general rule AF remains functional as long as the combination has a max. aperture equal of bigger than f/5.6 (or f/8 in case of the Canon EOS 1v and EOS 3). Some lens + third-party converter combinations don't seem to work regardless of this rule (?).
Don't expect wonders with the 2x converters - these are usually too much for many lenses regardless whether it is the Canon EF 2x or the Kenko AF Pro 2x. Only ultra-high performance lenses like the 300/2.8 (IS) or 400/2.8 II (IS) manage to produce a very good performance here.

[lobohuang]

thx a lot