Hello.
I use Graff px v.1.0.30d.
I notieced that the results of Histogram Equalization differs from the results, achieved with Photoshop CS 5.

The histogram Equalization works with the pixel intencities, which are calculated from values of all the 3 color channels. Adobe Photoshop and Graff px, calculate the intencity in a different way. That was disscused in this topic:
http://www.project-10.de/forum/viewtopic.php?f=20&t=183(where C stays for the pixel intencity)