100 400 L plus 1.4x

[d70mpv]

Have just got the pump plus the L 1.4x too on a 40D, can anyone tell me if I'm supposed to get a 'chirrup' and red flashing AF point when the focus is locked in manual mode with the extender attached? I get this in manual without the extender...

[Hobjob]

I'm away from home so away from my main notes so I can't answer in full.

You do need to tape up 3 of the terminals on the extender to make autofocus work - the details are around on google though.

Even taped autofocus hunts a bit except in good light.

[d70mpv]

Hi, thanks for the info. I seemed to have answered my own question by having a go with the lens set to MF using the lens switch and using the T/C with and without the pins taped. The red flashing focus point in the viewfinder and the bleep are only activated when the pins are taped.

I hope this will avoid any potential for USM motor burn-outs if the focus motor constantly hunts a long distance when the pins are taped and the lens is in AF mode...