This thread is much of a replay of one some time ago. I have not had time to analyse his software but gromit appears on the right track. The logic is quite clever . What is produced is not an increase of contrast but a redistribution of luminosity It is oftern of value to attach the curves or levels layer to the top duplicate mask layer. The technique can be used with colour but saturation can vary across the tonal range so a saturation protection layer should be placed above the mask layer. The technique greatly improves many images but is detrimental or non-effective to others. It is one of many approaches and may form part of a sequential strategy to be considered when edition images for perceptual qualities. The paper Bob and others have referred to , published in Leonardo Journal (MIT Press)- , is related not to this but to directed differential acuity. Applications of both are outcomes of the psycho physiological approach to printmaking that George de Wolfe uses which he derives from Minor White and others. The theoretical base was studied at RIT by Richard Zakia , Lesley Stroebel and others. Going back further one should refer to E.H Gombrich's "Art and Illusion"' 1959, derived from the 1956 A.W.Mellon Lectures in The Fine Arts. I would have to say that this can be deep stuff. It is not easy for those with a Cartesian approach to photography and printmaking. It can also produce terrrible results if one is not on top of it.
I would suggest that seeing the differences these edits make is a learned skill and is not possible on a computer screen or even from a book. I recall seeing original Ansel Adams and Paul Caponigro prints with and without the framing glass. The difference was astonishing. The difference was presence, and that is what George de Wolfe is talking about.
