BBF on lens button

[Itsbigmal]

Hi There, I'm trying to set up Back Button Focus that is activated from the 100-400 lens button. My hand just sits in the right place and need it to use AF/C for fast moving subjects, cant seem to get the right command in in the list of options. I did have it set on AEL but have reassigned that to something else. Many Thanks

 

[GvilleRick]

Which camera do you have? On my a7RV I was able to set it with these menu selections:

Setup Menu
Operation Customise
Custom Key/Dial Set (Photo or Video option as you want to set)
Lens
Select the Focus Hold Button
AF/MF
AF On