Contrast enhancement is, as we've implemented it in ACE, all about the luminosity. Grayscale images are just fine here. But people like to work on colour images, so the filter converts them to grayscale before processing, and then tries to figure out how to put the colours back in when it's done. That's the part we we're still working on getting right.
The current development version of ACE has a whole mess of colour options, which will continue to be added, tweaked, and removed until we figure out which ones actually work. This page is an attempt to document the issues we're dealing with. There's a similar attempt in the "doc" directory of the plug-in distribution, but it doesn't have any pictures.
These issues aren't specific to ACE, nor do they really lie within its domain. Perhaps this means they should be treated seperately. But how?
One idea: Have ACE create channel masks over areas which it believes will be trouble spots. Then using these masks for selections, the user can correct the troubled areas with tools such as Sample Colorize.
Questions, comments, reservations, and pointers to appropriate resources are strongly encouraged and appreciated. Please mail them to the address at the bottom of this page.