1.4X Extender with Canon 100-400IS

Started Jul 19, 2001 | Discussions thread
Fred Miranda Senior Member • Posts: 2,469
Very interesting..

I use the Kenko PRO 300 1.4x with my 100-400IS and it behaves the same as the Canon 1.4x, the camera changes the aperture automatically to f/8 and you can't use AF.

So with the 100-400IS or lens with 10pins, both third parties and Canon's extenders deactivate the lens AF. (I only have experience with the Kenko though).

Do you think that taping the pins on the Kenko teleconverter would "enable" AF when with the 100-400IS as well?
This may be good news for a lot of us.

Frederico Miranda

XXX wrote:
I have a Canon 1.4X extender. I have other brands as well.
The Canon is the only one that does not try to autofocus with
the 100-400mm IS lens. The other telextenders have a simpler coupling
which does not pass through to the camera the aperature correctly.

With these telextender it believes the the lens is still an f5.6
lens while using the extender so it autofocuses. With the Canon
the camera knows that wide open is f8. I am sure some features may
need this information but for general use the camera still exposes
correctly with the other telextenders.

I wanted the Canon telextender quality and yet be able to have the
auto focus try to work. It is true that in low light that the
focus works very poorly or not at all, but still in many cases
outdoors I shoot bright objects. Bad autofocus is better than no

I put a piece of tape on top of the three end pins on the left hand
side of the telextender looking at it from the lens connection
side. With these three left pins covered the telextender continues
to operate on the D30 WITH AUTOFOCUS ACTIVATED!. I taken around 50
pictures with this modication and I happy with the results to date.

I am not sure what the modication does but I did it because the
other telextenders do not have these three pins. I hope does no
harm to the camera or lens, I cannot be sure I have had no
problem. I only provided this information so that other can see the
results of what I have done. Try it on your own camera and lens at
your own risk.

Luis Correa wrote:

Has anybody tried the 1.4X extender with Canon 100-400 IS? Please
advise. Thanks

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