1. A method, comprising: accessing a digital image frame of a scene, the digital image frame originating from a camera module; in response to detecting a face area in the digital image frame, performing by a processor: calculating a face chromaticity from the face area detected in the digital image frame; determining a lighting condition at the scene associated with the digital image frame; and comparing the face chromaticity with a reference face chromaticity for the lighting condition to determine a chromaticity gain shift; and calibrating a gray point curve of the camera module based on the chromaticity gain shift to obtain a calibrated gray point curve for the camera module.