I just recently acquired the new Sony A7R4 mirrorless full frame camera, and have been working through the focusing systems on this camera. One of the questions that comes up is whether or not to use back button focus.
As you can see, it has an “AF ON” button on the back that would be perfect for this. All you need to do is to go into the menu and set the “AF w/ Shutter” option to “OFF”. This prevents the shutter button from activating auto focus, and instead you can activate the auto focus via the “AF-ON” button on the back. I assigned the “Focus Mode” to the C3 button on the back, and set the focus mode to “AF-C” (continuous autofocus). So, how did this work out?
Well, back button focus works as you would expect. However, I ran into 2 issues:
- When someone offers to take my photo with my own camera, I normally set the shoot mode dial to “fully automatic” before handing it over. On my Canon M50, this then re-enables auto focus on the shutter button, so that when the other person presses the shutter button, the camera will focus itself. The Sony doesn’t do this, and unless the person presses the “AF-ON” button on the back first, the picture will be out of focus
- Because the Sony doesn’t have a flippy screen that flips around to the front, when you take a selfie you need to use an app on your smart phone to frame the picture. You can trigger the shutter from the app, but there is no way to get the camera to focus without reaching around behind the camera to push the “AF ON” button. The Canon app has a separate auto focus button when the camera is set up for BBF, but this is completely lacking on the Sony.
Turning off BBF solves these issues, but sometimes you really don’t want the camera refocusing when you press the shutter button. Also, it is nice to be able to check and tweak the focus manually after auto-focusing, but this doesn’t work unless you put the camera in “DMF” focus mode. So, what’s the best way to set up the camera to allow the shutter button to do autofocus normally, but suppress it easily when wanting a back-button or manual focus bevahiour?
I looked into Mark Galer’s Focus masterclass, and looked at some other blogs for how people do BBF. After some playing around, I’ve come up with the following setup:
- The “AF w/ Shutter” option is set to “ON” to allow the shutter to trigger the auto focus under normal conditions. The “C3” button is assigned to “Focus Mode”, and here I would normally select “AF-C”. I can choose the appropriate “Focus Area” setting using the “C1” button, which I typically set to “Wide” or “Tracking Flexible Expanded Spot”. The latter lets me do a “focus-recompose” action with the shutter half depressed, and the camera will keep tracking the subject I first selected when half-pressing the shutter. Manual focus adjustments generally won’t work with this setup (it depends on the lens).
- The “AF-ON” button gets assigned to the camera’s “custom hold recall” feature. This allows us to define some settings that should be overridden with a special profile while ever the button is held down. In the custom hold profile I set it to temporarily set the Focus Mode to “DMF” and to enable “AF-ON”. If I hold in the “AF ON” button, the camera goes to DMF mode, which will auto-focus using the currently selected “Focus Area” setting, and allow me to tweak the focus manually. While holding in the “AF ON” button I can then press the shutter and it will take the shot with my manual focus adjustment in place.
- If I want the camera to completely decouple the shutter button from auto-focusing ( as in BBF) I use the “C3” button to set the focus mode to “Manual Focus”. I can now focus manually at will, and if I want the camera to auto-focus I just hold in the “AF ON” button. Once I release the “AF ON” button, the camera is back in manual focus mode, and I can depress the shutter without affecting the focus.
- If I want to take a selfie, I just need to use the “C3” button to set the Focus Mode back to “AF-S” or “AF-C”.
- If I want to hand the camera over to someone else to take a picture, I use the shoot mode dial to recall one of the memory profiles (I use M4). This puts the camera in fully automatic, set the “Focus Mode” to “AF-C”, and sets the “Focus Area” to “Wide”, to make the camera as idiot-proof as possible.
By setting the “AF ON” button to use “DMF” as an override, it allows me to do manual focus adjustments even if the camera is in automatic focus mode. However, like this it will do a one-shot focus and then wait for any manual adjustment. Sometimes when people use back-button focus, they want the camera to do continuous focus while ever the back button is held in. I’m not too worried about this, because if I want to do AF-C, I can just use the main shutter button. However, if I have put the camera in manual focus mode to get a true BBF effect, then it would be preferable to override the focus mode to “AF-C” rather than “DMF”. This could be assigned to another button, like the “AEL” button. While ever the AEL button is held in, the camera will continuously auto-focus, and when the button is released it will revert to manual focus while will allow any last manual adjustment before releasing the shutter. Maybe I’ll do that some time, but at the moment I have the AEL button to be my “oh quick, put some sensible settings in to get this sudden unexpected action shot” button.
Just another nice feature I discovered is with the multi-selector joystick control. If you push it in while you are in AF-C mode, then it will either center the focus box, or it will act as an “AF-S” back button focus. The AF-S in Sony cameras will give you a more accurate focus than AF-C since it does a contrast-based focus check at the end to verify focus. Holding in the multi-selector and then squeezing the shutter will result in a more accurate AF-S focus, provided you were in a “Wide” or “Centre” Focus Area mode.
So, that’s the way I’ve set up the camera for now — normally in AF-C mode triggered by the shutter button, with easy manual focus override via “AF ON” button, and the possibility to drop into BBF mode by setting the camera to manual focus with button “C3”. (I could also set up button “C3” to simply toggle between AF and MF, I’ll use the camera for a bit and see if it is worthwhile).
Feel free to comment if you have other suggestions to allow for easy transition between auto-focus, BBF, selfie and third-party/untrained user workflows.