Back-Button Focusing (BBF) is an autofocus configuration in which autofocus activation is separated from the shutter release.
On the Fujifilm X100VI, BBF changes when autofocus is allowed to operate.
It does not modify autofocus accuracy, speed, or detection algorithms.
This post explains what BBF does, what it does not do, and how to implement it using only controls and menu items that are available and functional in the described configuration.
BBF does not make autofocus faster.
It makes autofocus explicit.
Why Back-Button Focusing Exists
In the default autofocus configuration, the shutter button performs two actions:
A half-press initiates autofocus and exposure metering.
A full press triggers image capture.
Because autofocus is linked to the shutter, any interaction with the shutter button can trigger a focus operation.
Back-Button Focusing separates these actions.
Autofocus is assigned to a dedicated control.
The shutter button is used only to trigger image capture.
This separation is the sole purpose of BBF.
BBF does not change autofocus performance.
It changes when autofocus is allowed to run.
What BBF Changes in Practice
BBF does not alter autofocus modes, detection logic, or lens behavior.
It alters the conditions under which autofocus is activated.
Focus activation becomes explicit
With BBF, autofocus occurs only when the assigned AF-ON control is pressed.
Releasing the shutter or recomposing the frame does not trigger autofocus.
Focus remains at the last acquired distance until AF-ON is pressed again.
Focus state remains stable across multiple frames
After autofocus is acquired via AF-ON, multiple frames can be captured without any additional focus operation.
Focus changes only when the AF-ON control is pressed again.
Control separation is consistent
One control is used to request autofocus.
One control is used to trigger image capture.
This behavior remains consistent as long as the configuration is unchanged.
Implementing Back-Button Focusing on the X100VI
On the X100VI, a fully isolated BBF configuration relies on Manual Focus mode combined with AF-ON.
This is not a workaround.
It is the only configuration in which autofocus can be invoked exclusively via AF-ON and never via the shutter.
Set the focus mode using the physical selector
On the left side of the camera body, set the focus mode selector to M.
This is a physical control that overrides menu-based autofocus modes.
When the selector is set to M:
Autofocus cannot be triggered by the shutter button.
Autofocus is available only via AF-ON.
Focus remains fixed until AF-ON is pressed.
Assign autofocus to the Rear Command Dial (Press)
MENU → SET UP → BUTTON/DIAL SETTING → FUNCTION (Fn) SETTING
Select Rear Command Dial (Press).
Assign AF-ON.
In this configuration, pressing the rear command dial triggers autofocus once at the active AF point.
No other control initiates autofocus.
Disable autofocus from the shutter button
MENU → SET UP → BUTTON/DIAL SETTING → SHUTTER AF
Set SHUTTER AF to OFF.
In Manual Focus mode, this setting has no operational effect because the shutter cannot trigger autofocus while the focus selector is set to M.
This setting ensures that autofocus remains disabled from the shutter if the focus selector is later moved out of M.
Autofocus Behavior in Manual Focus Mode
When the focus selector is set to M, the X100VI operates under a specific autofocus logic.
Autofocus modes such as AF-S and AF-C are inactive and not selectable.
Continuous autofocus is not available.
Pre-AF is inactive and not selectable.
Each press of AF-ON triggers a single autofocus operation.
After focus acquisition:
Autofocus stops.
Focus remains locked at the acquired distance.
No further focus updates occur until AF-ON is pressed again.
This behavior is fixed and cannot be configured or modified.
In Manual Focus mode, AF-ON always behaves as a single, momentary autofocus request.
BBF Operational Workflow
Once configured, BBF follows a consistent operational sequence:
Press the AF-ON control to acquire focus.
Release the control.
Recompose if needed.
Trigger image capture one or multiple times.
Press AF-ON again only if subject distance changes.
The camera does not initiate autofocus automatically at any stage.
Using Drive Modes with Back-Button Focusing
Back-Button Focusing can be used in combination with the camera’s continuous drive modes.
Using a drive mode allows multiple frames to be captured during a single shutter press, while autofocus behavior remains unchanged.
Autofocus is triggered only when AF-ON is pressed.
During a burst sequence, no autofocus operation occurs unless AF-ON is pressed again.
This allows several frames to be recorded at the same focus distance.
In practice, this can be useful in situations such as street photography, where small variations in gesture, expression, or timing may occur within a very short interval.
The use of drive modes does not change focus accuracy or focus position.
It only affects how many frames are captured while the shutter button is held.
Sensation at Shutter Release
Some users perceive a slight mechanical or tactile sensation at the moment of exposure.
This sensation occurs even when autofocus is not active.
It does not indicate autofocus operation.
It does not alter the focus position.
This behavior is consistent with leaf shutter operation and internal exposure validation.
Why Certain Autofocus Menus Are Unavailable in Manual Focus Mode
When the focus selector is set to M, several autofocus-related menu items become unavailable or permanently disabled.
This includes options such as:
AF MODE (AF-S / AF-C)
PRE-AF
This behavior is intentional.
On the X100VI, physical controls take priority over menu logic.
When the selector is set to M, the camera does not operate in an autofocus mode that supports continuous or predictive behavior.
As a result, menu items that apply only to those modes are removed.
In Manual Focus mode, autofocus can occur only when explicitly requested via AF-ON.
Closing Notes
Back-Button Focusing on the Fujifilm X100VI does not improve autofocus performance.
It changes when autofocus is allowed to operate.
In a Manual Focus + AF-ON configuration, autofocus becomes:
Explicit
Momentary
User-initiated
Predictable
The camera does not update focus unless explicitly instructed to do so.
This configuration aligns with the X100VI’s control hierarchy and produces consistent, repeatable behavior without relying on inactive or inaccessible settings.