The tutorial on luminosity masks was very helpful, but when it talked about midtones it was wrong. It states that midtones are the intersection of the light tones and the dark tones. These regions never intersect. The result of intersecting any light tone with a dark tone is an empty map, which means the map will include all tones.
The midtones are what are left when you subtract the dark tones and the light tones from the total luminosity map. Also, using the masks named in this tutorial as L and D together will result in and empty map since together L and D encompass all tones. You have to start with LL and DD.
I am surprised this has remained uncorrected for so long. Tutorial videos have been produced based on this tutorial or the one from which it was derived.
