A head-worn device, comprising: a camera (316a, 316b) configured to generate first pixel data from a field of view of the head-worn device; a display device to display second pixel data to a wearer of the head-worn device based on the first pixel data captured by the camera; weld detection circuitry configured to: determine whether a welding arc is present; and generate a control signal indicating a result of the determination; and pixel data processing circuitry configured to process the first pixel data captured by the camera (316a, 316b) to generate the second pixel data for display on the display device, wherein a mode of operation of said pixel data processing circuitry is selected from a plurality of modes based on said control signal; characterised in that: the head-worn device further comprises a receiver circuit configured to receive a communication to indicate whether a weld current is flowing through a weld torch; the weld detection circuitry is configured to receive a signal representative of the weld current flowing through the weld torch; and the weld detection circuitry is configured to determine whether a welding arc is present based on the communication received from the receiver circuit. a camera (316a, 316b) configured to generate first pixel data from a field of view of the head-worn device; a display device to display second pixel data to a wearer of the head-worn device based on the first pixel data captured by the camera; weld detection circuitry configured to: determine whether a welding arc is present; and generate a control signal indicating a result of the determination; and pixel data processing circuitry configured to process the first pixel data captured by the camera (316a, 316b) to generate the second pixel data for display on the display device, wherein a mode of operation of said pixel data processing circuitry is selected from a plurality of modes based on said control signal; characterised in that: the head-worn device further comprises a receiver circuit configured to receive a communication to indicate whether a weld current is flowing through a weld torch; the weld detection circuitry is configured to receive a signal representative of the weld current flowing through the weld torch; and the weld detection circuitry is configured to determine whether a welding arc is present based on the communication received from the receiver circuit. determine whether a welding arc is present; and generate a control signal indicating a result of the determination; and pixel data processing circuitry configured to process the first pixel data captured by the camera (316a, 316b) to generate the second pixel data for display on the display device, wherein a mode of operation of said pixel data processing circuitry is selected from a plurality of modes based on said control signal; characterised in that: the head-worn device further comprises a receiver circuit configured to receive a communication to indicate whether a weld current is flowing through a weld torch; the weld detection circuitry is configured to receive a signal representative of the weld current flowing through the weld torch; and the weld detection circuitry is configured to determine whether a welding arc is present based on the communication received from the receiver circuit. the head-worn device further comprises a receiver circuit configured to receive a communication to indicate whether a weld current is flowing through a weld torch; the weld detection circuitry is configured to receive a signal representative of the weld current flowing through the weld torch; and the weld detection circuitry is configured to determine whether a welding arc is present based on the communication received from the receiver circuit.