1.4X Extender with Canon 100-400IS

Started Jul 19, 2001 | Discussions thread
XXX New Member • Posts: 3
I modified the Canon 1.4X to include autofocus

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 autofocus.

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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