Abstract: In a digital image having pixels pi (i=1, 2, . . . ) and a brightness B(pi) at each pixel pi, the global dynamic range of an image is changed by replacing the brightness B(pi) with the brightness B*(pi)=B(pi)×(B0/Bavg(pi))?, where B0 and ? are predefined constants, and Bavg(pi) is some average brightness value, e.g. the mean brightness over a region R(pi) containing the pixel pi. The local dynamic range is not changed significantly in some embodiments. The brightness of an image at a pixel can be defined so that multiplication of the brightness by a positive value k corresponds to multiplication of tristimulus values by k. In some embodiments, a color coordinate system is used with the brightness being one of the coordinates.