T3i with 100-400 + 1.4TC, will AF work?

[privatebydesign]

Tag says it all really, but I was just asked if the 100-400 with Canon 1.4TC would AF on the T3i, I don't have a clue.

If the T3i AF is limited to f5.6 but the first part of the zoom retains that what happens?

Thanks.

 

[Mt Spokane Photography]

When you add the 1.4X TC, the lens will not focus on a T3i because it is now a f/8 lens at longer focal lengths. Even at 100mm it will be a issue.

However, it is possible to tape the contacts which feed back the aperture information to the camera, and it will autofocus, but may be slow or hunt a bit. In bright light, it works better than poor light.

http://www.michaelfurtman.com/taping_the_pins.htm

 

[candc]

It will work with a kenko

 

[privatebydesign]

Thanks, I suppose what I am asking is what, exactly, happens with the AF and a variable aperture zoom when used with the TC when the starting aperture is good for the AF but the longer length isn't?

Does the AF work as normal at 100mm up to wherever the new aperture hits over f5.6, or does it never work, do you get a warning of some kind etc etc.

 

[candc]

It won't work with the canon tc. The camera recognizes the combo and will not allow autofocus. Apparently you can tape some of the contacts and then the af will engage

 

[Loswr]

Thanks, I suppose what I am asking is what, exactly, happens with the AF and a variable aperture zoom when used with the TC when the starting aperture is good for the AF but the longer length isn't?

Does the AF work as normal at 100mm up to wherever the new aperture hits over f5.6, or does it never work, do you get a warning of some kind etc etc.

Phase AF is disabled by the firmware when the lens + TC is mounted. Live View AF will work.

 

[privatebydesign]

Thanks all, Neuro in particular. I have passed that information along.