1. A method of normalizing the lighting changes in an input image comprising an X and Y array of pixels having various illuminating intensities, said lighting changes having an additive effect and a multiplicative effect on said input image, said method comprising the steps of: estimating said additive effect from said input image to provide a background estimate; deriving high and low quantile maps of said input image; estimating said multiplicative effect from said input image to provide a gain estimate by taking an absolute difference between said high and low quantile maps and said estimate of said additive effect; subtracting said background estimate from said image; and, normalizing said image with respect to said gain estimate; wherein said method is implemented as an algorithm: ##EQU3## wherein .GAMMA.(x,y) is a normalized image, .GAMMA.(x,y) is the effect of said lighting changes, said additive effect is .beta.(xy) and said gain estimate is .alpha.(x,y).