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# init(device:action:)

Creates a slider to control the exposure bias of the specified capture device with an action to respond to exposure bias changes.

```
init(device: AVCaptureDevice, action: @escaping @MainActor @Sendable (Float) -> Void)
```

## Parameters

`device`

The capture device to control.

`action`

An action the system calls on the main actor to handle changes to the device’s [`exposureTargetBias`](/documentation/AVFoundation/AVCaptureDevice/exposureTargetBias) property.

## Discussion

The system only calls the specified action when the exposure bias slider changes the device’s [`videoZoomFactor`](/documentation/AVFoundation/AVCaptureDevice/videoZoomFactor) property value. If you need to react to other sources of changes to the exposure target bias, use key-value observation instead.

> Important:
> Don’t change the capture device’s exposure target bias when the system calls the action.

---

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