400L 5.6 and teleconverter

I apologize if this has been covered, but I did a search and did not find a satisfactory answer to the following question: is there a teleconverter made that can be used with the L400 5.6 so that autofocus is not lost?
I would like to get the 400 5.6 to use for bird photography, and the addition of a teleconverter would be great.

I believe the Tamron 1.4 will do the job.

The Canon 1.4x TC I believe will also.

Really? I could have sworn you loose AF with the canon TC...

I read that the AF mechanism will be lost on the digital rebels, 20D and 30D with the canon 1.4 converter, but will be retained on full frame cameras. I have a rebel XT, and will most likely stay with the smaller sensors.
Seanm, which tamron 1.4 teleconverter are you referring to? I see more than one mentioned on the B&H website.

You'll lose AF with the 30D. You'll retain AF with the 1-series bodies. However, if you tape certain pins (not sure which), the aperture won't be reported to the camera, and so AF will remain (though it won't be very good).

cjm wrote in post #2422325
The Canon 1.4x TC I believe will also.

Only if you tape the last three pins to fool the camera into thinking that a tc is not present. I use a Canon 1.4 with the 400mm f5.6 in this way.

You could buy a non reporting tc (kenko 1.5x, not the teleplus pro series) and not lose AF but it can be slow focusing...don't know that I'd do it.

Roy C wrote in post #2422453
Only if you tape the last three pins to fool the camera into thinking that a tc is not present. I use a Canon 1.4 with the 400mm f5.6 in this way.

If you tape the pins on the canon, is the af as fast as without the pins? Does the lens seem to search?

iterrier wrote in post #2423956
If you tape the pins on the canon, is the af as fast as without the pins? Does the lens seem to search?

it hunts a lot....

cheers....

kross wrote in post #2424016
it hunts a lot....

cheers....

I'm imagine it be a pain, especially in bird watching when it hunts and the birs is gone by the time it's finally able to take a shot.

Broncobear wrote in post #2424028
I'm imagine it be a pain, especially in bird watching when it hunts and the birs is gone by the time it's finally able to take a shot.

yup, my mfing is faster than using the af with 1.4x tc....

cheers....

OK... simple facts. On all Canon digital SLRs (apart from the 1 Series cameras) the AF mechanism is rated to work with lenses with a maximum aperture as small as f/5.6. If it sees a lens with a smaller max. aperture than that, then the camera disables AF.

You can get a "non-reporting" teleconvertor which doesn't tell the camera about the new effective max. aperture or you can tape the pins on a reporting TC in order to fool the camera. However, if you do this, then you are running the AF mechanism outside of specification. In bright light then you might get away with it and it may even work quite well, but in lower light conditions the lens will start to hunt and it may fail to AF completely.

Thank you all for your replies. I will keep this all in mind. Maybe I'll just get the 400 5.6, and see how much I miss I longer reach before I consider a tc.

The cheap Tamron 1.4 ( the one with only eight contact pins ) works pretty well on the 400 f 5.6. By pretty well I mean tha the IQ is excellent but the AF is a little slow. I tried the Canon with taped pins but found it to be very slugish by comparison.