| CPC G02F 1/13725 (2013.01) [G02F 1/1323 (2013.01); G02F 1/133509 (2013.01); G02F 1/13712 (2021.01)] | 14 Claims |

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1. A display apparatus comprising:
a display device arranged to display an image and capable of operating in at least a public mode and a privacy mode, wherein to an on-axis viewer the visibility of the image is such that the image remains visible in both the privacy and public modes, and to an off-axis viewer the visibility of the image is reduced in the privacy mode compared to the public mode;
an ambient light sensor arranged to detect the illuminance level of the ambient light; and
a control system arranged to control the display device, the control system being capable of selectively operating the display device in the public mode or the privacy mode,
wherein the control system is arranged to selectively control luminance of the displayed image in the public mode in accordance with a public transfer function that relates varying levels of luminance to detected levels of the ambient light and to selectively control luminance of the displayed image in the private mode in accordance with a privacy transfer function that relates varying levels of luminance to detected levels of the ambient light in the privacy mode, the privacy transfer function being different from the public transfer function.
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