Sometimes FSAA (my acronym for Fast Stone auto-adjust) is similar to PWP Special Effects | Equalize at some amount, but often it is different. FSAA is frequently too bright, but it distributes contrast well.
FSAA is useful while processing an image in PWP. One way is simply to see what FSAA does to an image, suggesting possibilities. Another way is to incorporate an FSAA transformation in the course of PWP work. Open a PWP working image in FastStone, apply FSAA and take a look, and save if desired. PWP working images are files with names pw_image_nn.tif. The nn's do not correspond to the window numbers we see in PWP, but the largest nn is the most recent window. When I save in FastStone, I name the file something like FSAA_nn.tif, opening that file in PWP to continue.
Here is a general description by Andras Horvath, author of the auto-adjust package:
Horvath's remark is in the core source file, aargb.c, part of the package released under GNU open software license. There is more information in the code itself for those who read the C programming language, and additional comments in Hungarian. The package is available via http://log69.com/downloads/aaphoto_sources_all.tar.gz . FastStone is at http://www.faststone.org/ .pictures might need some contrast adjustment when their colors don't spread the entire spectrum, usually when their darkest colors aren't dark enough and the lightest colors not bright enough, this causing a veiled effect on them.
sometime color balance adjustment is also necessary, when the brightest and darkest colors of the image are not black and white enough, but they are shifted towards some other color which may be the effect of the technology used, or simply the environment changes the colors unrealistically.
the procedure assumes that there must be some detail on the picture that's supposed to be black (dark enough) and also white (bright enough) in real. the automatic contrast and color balance process is built upon this.
the overall (or average) brilliance of the image can be set by the gamma level. this procedure makes sure that those pictures that seem too dark will be corrected by this factor by changing the middle dark colors while not changing the darkest and brightest colors.
as the last step, a saturation adjustment takes place to intensify the colors themselves if needed.