2Xii teleconverters

can someone tell me what that button is on the side of the converter? i just got one from Andoroma today...

I cant use the AF either.. is this typical with the teleconverters? i have the cannon 70-200 1:4 L lens

Unless you have a 1-series body, the camera can't AF at apertures beyond f/5.6; the 2x TC on a 70-200 f/4 has a maximum aperture of f/8. So no AF. The "button" is the lens release.

ok thank you so much!!

I was beaten to the punch... Ah well.

One of the side effects of using a 2x Tele is that it will result in a 2 stop loss to whatever lens it is attached. So your 70-200 F4 becomes a 140-400 F8. Unfortunately, your body can only autofocus when the minimum F is 5.6.

You would be been better served going with the 1.4 Tele which would have resulted in a 1 stop loss or F of 5.6

There is a simple solution to the autofocus issue. Tape the pins.
http://www.michaelfurt​man.com/taping_the_pin​s.htm
You do need lots of light, but the AF will work.