Sony a7r3 back-button focus

[joker200]

I have set-up back button-focus with AF-ON set as my "focus hold" button. I use AF-S, and my understanding is that once the button

is pressed, focus is locked and I don't need to hold down the button. Now, when I'm in AF-C I'm using phase detection now and I NEED to hold

the button down to keep focus, but the system can now adapt to movement in the frame.

 

Is this accurate ? 

I have had trouble confirming this information.

 

 

Thank you-? 

[Thad E Ginathom]

I don't have that camera, but from my a6500 experience...

The default behaviour of the AF button is to toggle AF on/off, ie to switch between AF and MF.  If you have AF on, focus the camera, and press to turn AF off... the focus stays where it is. Isn't that what you want to happen?

General Sony button-menu language is that hold holds while you hold, and releases when you let go. Toggle switches between two (or more?) states and remains on the one that you pick.

[dbmiller]

Correct - AF-S will focus once when you press the button assigned to "AF On", and you are locked at that `focal distance. You can recompose or leave the camera in a fixed position and the focus distance does not change. If the distance to your main object of focus changes, then it will be out of focus. So if your recompose technique is flawed, or the subject moves, you may not have what you want it focus.

AF-C will continually focus while camera is trying to acquire focus. So if you have BBF set up, it will continue to AF until you release the button and now it's locked at whatever distance you were at when you released the focus button.

There is an argument to be made that with AF-C, eye-AF,  movable focus points, and tracking options, that BBF is not needed anymore. It depends on what you're doing with it. If you really want that focus distance locked in, then using BBF is fine. But if you or your subject is moving, then AF-C and one of the other modes will often work out better.

[joker200]

thanks everyone, answered my questions perfectly.