SABATIER
The digital sabatier uses the colour curve to make a rendition of the original sabatier done in a darkroom to a partially developed print. In that process, light was added while the print was traditionally still in the developer bath, and well before it was completely developed to allow for the development of the traditional outlines of black, known as mackie lines, and the varying values of tone.
In working a digital sabatier image, light is not added it is just moved around to make the characteristic mackie lines and tonal shifting of the original process.