Steve Ohio If I choose to rescan the root folder containing the library of my pictures, is it going to re-examine all the pictures and re-suggest faces in all pictures?
This button only looks for changes in selected folder. Typically that would happen anyway during regular rescan, but with that button you can rescan selected folder right now.
Steve Ohio When I choose to rescan an individual folder in the library, is it going to re-examine only the pictures in that sub-folder and re-suggest faces.
No. It will only look for changes. And if there are new files - it will do full analysis of them, including face recognition. But for files that did not change it will do nothing. If you want to force re-index of some existing files, you should select them and do “Re-index files” command from context menu.
The thing is, when you move file, this will constitute a change. Tonfotos detects that one file was deleted and another was added to the library at new location. And that new file undergoes all sorts of analysis, including faces detection. Theoretically, it can detect that this is the same file, just moved to another location, but right now there is no such detection mechanism.