Hi Wade,
The default parameter values in PixInsight's GREYCstoration implementation were suggested by David Tschumperlé, the author of the GREYCstoration algorithm. David kindly (and patiently!) assisted me during my development of the PixInsight module.
Be careful with anisotropy when applying GREYCstoration to astronomical images. In general, you want to preserve isotropy, especially on deep-sky images.
PixInsight has added several new parameters
I implemented all the parameters available to control the GREYCstoration algorithm. There are a few ones, however, that are of little practical use. For example,
Fast Approximation should be left at its default state (selected). In general,
Interpolation does an excellent work with its default "nearest neighbor" value, but you may try with "bilinear" or "2nd order Runge Kutta" which may provide slightly more accurate results sometimes.
The only parameter that is PixInsight's exclusive is
Coupled channels. This option must be enabled for normal GREYCstoration operation on color images. If you disable it, then each color channel will be processed as an independent grayscale image. Note that this is opposite to GREYCstoration's working philosophy, in which the whole color image is treated as a unique structure. However, processing each channel independently may be useful sometimes for deep-sky images.
I'm hoping some day, Juan will have enough time to do a tutorial about GREYCstoration using general landscape images.
I am probably more lost than you as for GREYCstoration parameters. I think the most critical parameters are
Noise scale,
Sharpness and
Amplitude. These are the parameters I normally use. I must recognize that I have little direct experience with this tool.
So I look forward to whatever you can find and learn!
