100-400mm with 1.4x on 5DM3

Anyone try this? Will it focus?

I haven't tried it but it should not work. None of the MkIII AF points are better than f/5.6

Of course you can tape the pins. Then it will AF on any Canon camera assuming enought light and contrast.

benttop wrote in post #14598773
Anyone try this? Will it focus?

I assume you want to use it at 400mm. No it won't work. You need a 1D and even then it will only work with the center AF point.

Interesting. The manual on the extender seems to imply that it should work, but I know it didn't work with my 5DM2. Am I misreading this? http://gdlp01.c-wss.com …xtender-ef-14x-iii-en.pdf

That PDF doesn't mention which combo's will AF and which won't. It just has the exceptions on MFA for some lenses.

Yeah - it will mount -- but that does not mean it will autofocus....

f/6.7 will not autofocus on most cameras.

<sigh>... it's a pity.

On some lenses AF will be retained. If the final aperture is f/5.6 or less, you have AF. On the 100-400 at 400, you are already at f/5.6 so adding the t-con pushes you over the limit.

Again, if AF is critical, tape the pins so that it won't report. The AF will work if there is enough light and contrast. I've had the 100-400 AF on a XT with taped pins.
http://www.michaelfurt​man.com/taping_the_pin​s.htm

^+1
you can fool the camera by taping the pins or using non-reporting extenders like some kenko and tamron's.

AF is slow however and I found it useful for static subjects only.

Taped pins used to work on the 5D, but it had clumsy AF points. I tried this on the 7D and I had no joy at all.

Taping the pins is a very simple operation that does no damage. Why not try it? It allows me to use my 100-400 and 1.4x on a 5D2.

But do read up on it first. Its only 3 of the pins, not all of them.

Generally speaking extenders should be avoided with zoom lenses other than f/2.8. Not only the AF may not work but the IQ won't be what you expect.

ydelta wrote in post #14600184
Generally speaking extenders should be avoided with zoom lenses other than f/2.8. Not only the AF may not work but the IQ won't be what you expect.

I have often used extenders with a 100-400 and don't find the IQ to be so bad that the images are unacceptable. I have to manually focus, but had to do that with film cameras for many years.

Here's a sample shot with a 1.4X on a 100-400.

Only problem with taping the pins is you get the glue from the tape all over the pins. There is also a slight risk that the tape / adhesive could make its way down into the camera.

thephotographynut wrote in post #14600529
Only problem with taping the pins is you get the glue from the tape all over the pins. There is also a slight risk that the tape / adhesive could make its way down into the camera.

I've used a taped Kenko 1.4x converter for several years now and I don't recognise what you say. Plain, boring old sellotape is what I used and its been fine.