> "Tom Pfeiffer" <[EMAIL PROTECTED]> wrote:
> The "standard" set of three Kenko tubes (12,20 & 36mm) do not support
> autofocus. The two that are sold separately (12mm and 25mm) do allow
> autofocus. I have the 25mm tube and the 20-35 Canon lens; if you
> would like me to do some specific testing drop me a note off of the
> list, but I don't have any dogs ;^)
Hi Tom and List,
There is some useful information on extension tubes and diopters
at the EOS FAQ. The list is out of date, but it shows magnifications,
incompatible combinations, and working distances:
http://bobatkins.photo.net/info/faq30/closeup.htm
http://bobatkins.photo.net/info/faq30/closeup2.htm
I think you will find that the Kenko tubes for Canon/AF mount will
indeed support autofocus. The Kenko tubes will NOT allow autofocus
only with a Nikon F5 and SWM lenses (but WILL work with Canon USM):
http://www.thkphoto.com/catalog/k/tubeset.html
On the other hand, if you use too much extension (e.g. 25mm extension
on a 20mm lens), the focus point might be INSIDE the lens barrel, and
focus (manual or automatic) may not possible.
Cheers
Julian Loke
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