1D Mark IV focus button locks exposure

[tt3008]

Hi!
Can anyone tell my why the focus button on the rear of my 1D mark IV locks my exposure? I have the camera set up to focus using only the rear focus button (not the shutter release). I tend to hold the rear focus button down when I'm shooting moving subjects (wildlife and children), but since I started using this focusing method my exposure is often wildly off when moving between say, sun and shade. So I have concluded that the focus button is locking the exposure. Does anyone know how I can fix this? I can't see anything obvious in the menus.
Thanks.

 

[Valvebounce]

Hi tt3008.
Welcome to the forum, I think this will be a custom function setting, linking the AFON button to exposure lock instead of metering start. Or just AF start with metering start on the shutter button.

Cheers, Graham.

 

[NorbR]

I checked with mine: I get the same behaviour, but only when AF is set to One Shot. When focus is locked, exposure is locked as well.
But when I switch to Servo (which I'd think you'd have when shooting moving objects), there's no exposure lock.

My C.Fn IV-1 is set to 2. Check your C.Fn IV-2 as well, that switches the functions of the AF and AE buttons on the back (although I imagine you would notice if your AF button did not AF anymore ...)

 

[tt3008]

I checked with mine: I get the same behaviour, but only when AF is set to One Shot. When focus is locked, exposure is locked as well.
But when I switch to Servo (which I'd think you'd have when shooting moving objects), there's no exposure lock.

My C.Fn IV-1 is set to 2. Check your C.Fn IV-2 as well, that switches the functions of the AF and AE buttons on the back (although I imagine you would notice if your AF button did not AF anymore ...)

Thanks for the suggestions. I am shooting on AI Servo (continuous). I still haven't got it to work, but I will keep at it. In the meantime I just have to remember to release the focus button every now and then.