A method characterizes manufacturing imperfections in a camera and variations in its operating environment to allow images captured by the camera to be compensated for these defects. The method includes: (a) illuminating a field of view of the optical elements under a controlled condition; (b) exposing multiple images onto the image sensor under the controlled condition; (c) extracting from the multiple images parameter values for pixels of the image sensor; and (d) compensating images taken subsequently in the camera using the parameter values. The controlled condition includes an external light source for illumination, and the image sensor is sensitive to color components.