These days anyone with a decent computer can edit photos for publication. The studies offered some useful rules that have stood the test of time. Viewers prefer to see realistic contrast in the area of the image that most interests them.
Viewers care much less about contrast in other areas.
Viewers generally prefer images that use the full range of tones from black to white. To show realistic detail, image contrast in this area should appear pleasing neither too exaggerated nor too flat even if other image areas must be sacrificed. Indeed sacrifice is often necessary, because on the printed page there isn't much depth of tone available compared to real life, the blackest blacks aren't very black, and the whitest whites aren't very white. Since we are much more sensitive to light tones than we are to dark ones, the lighter tones usually need to be given the lion's share of the available tone range, and the dark tones get what little is left. The following procedure should help you begin to edit photos.