Some photographs are not homogeneously light because the photographed object was not homogeneously illuminated. Fine details in the dark area of such photographs are hardly recognizable. We suggest a method to improve the quality of such images.
A known method used for correcting digital photographs taken by automatic devices installed on space probes on other planets uses the subtraction of the local mean lightness from the lightness of the pixels of the original image:
GVnew[x, y] = GVold[x, y] – Mean[x, y] + Const
where GVold[x, y] is the lightness ...