A method of automatic contrast correction comprises providing digital
image data, representing the data in the form of a brightness histogram,
determining a measure of central tendency for said histogram, adding a
shift value to the measure of central tendency to provide an adjusted
measure of central tendency, using the both the determined and adjusted
measures of central tendency to determine the exponent of a tone
reproduction curve, and applying the tone reproduction curve to the
brightness values of the image. Additionally, the method may provide
further correction by applying to the brightness values of the image an
S-shaped tone reproduction curve that does not change a measure of
central tendency of the brightness histogram.