A multi-purpose camera system includes an image capture block and an image signal processing block. The image capture block is arranged for generating an image signal, wherein the image capture block has an image sensor, an optical system, and a control circuit. The image signal processing block is arranged for processing the image signal. When the multi-purpose camera system is operated in a first operation mode, the multi-purpose camera system acts as a camera for generating a captured image output; when the multi-purpose camera system is operated in a second operation mode, the multi-purpose camera system acts as part of a user input apparatus for receiving a user input; and an overall configuration of the control circuit and the image signal processing block in the first operation mode is different from an overall configuration of the control circuit and the image signal processing block in the second operation mode.