Provided herein are teachings directed to overcoming the problem of erroneous color reproduction on a color output device such as a color display. The teachings herein provide a system and apparatus for correcting color image data input to a display device by displaying a target of color patches of known input values on the display device, and capturing an image of the target with a digital camera. This is followed by extracting camera signals from the image which correspond to the color patches, and deriving a tone response calibration for the projector from the camera signals and the input values.