To me, tonality is one of those vague terms that gets bandied about, often by people with at most a hazy idea what they mean by it. Don't be offended, or take that as a deep criticism: I might have to include myself in that! Sometimes I use / prefer the term 'tonal smoothness' or similar, meaning how subtle are the gradations; really bad tonal smoothness results in banding or big changes in adjacent colors unrelated to correspondingly-abrupt changes in the subject. Some people seem to use 'tonality' to mean something like what I might call 'tonal smoothness'. Others seem to use it to mean something more like gamut, or gamut in a particular area, or optical density range / contrast, or maybe something else entirely.