Hi I have a question, I am wondering can you put two 1.4 X extenders together and still have a sharp picture. Now I know this depends on the lens, so I am going to say, using it with a 300 f/ 4 is.
Thanks,
rw

I can say...they can't both be Canon, unless you put an extension tube between them.

And, unless you tape the contacts, you won't be able to AF on a 20D...adding two 1.4x will drop you to f/8 and the 20D can only AF to f/5.6.

Yes, you can do it and yes, 2 1.4x's will give you faster Af than a 2X but I do not think you'll be happy with the IQ on the 300/4 L IS.

Ok thanks to everyone for the answers, I have a chance to get a second Canon1.4 X , and was just wondering if it would be worth it.

Thanks again,
rw

Oh wait, I forgot, if you use two TCs the camera will only see one of them and think it's at f/5.6...so you will still have AF on the 20D.

You should be able to stack 2 1.4x TC since you can stack a 1.4x and 2x TC on one another. But picture quality woulden't be that great though.

EOS20 wrote:
You should be able to stack 2 1.4x TC since you can stack a 1.4x and 2x TC on one another. But picture quality woulden't be that great though.

That's just because the 2x has an empty space in the back of the lens for the 1.4x to fit in to. Two 1.4x canon converters will not fit together without an extension tube.

But you can mix a Canon 1.4x TC with a 3rd party 1.4x TC.