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The desired lens focal length; used for optical zoom.
This setting controls the physical focal length of the camera device's lens. Changing the focal length changes the field of view of the camera device, and is usually used for optical zoom.
Like CaptureRequest.LensFocusDistance and CaptureRequest.LensAperture, this setting won't be applied instantaneously, and it may take several frames before the lens can change to the requested focal length. While the focal length is still changing, CaptureResult.LensState will be set to MOVING.
Optical zoom will not be supported on most devices.
Units: Millimeters
Range of valid values:
CameraCharacteristics.LensInfoAvailableFocalLengths
This key is available on all devices.