If it helps, here’s a greyscale TIFF I constructed in Affinity Photo and then applied different contrast adjustments to the virtual copies in PL6.
Greyscale.tiff (833,6 Ko)
Greyscale.tiff.dop (106,2 Ko)
The important thing is to look at the histogram where, for the master copy, you should only see 11 vertical bars with nothing in between. In fact, there are a couple of small artefacts which must be a minute line between the segments, but not worth worrying about.
The VCs are named after the adjustments applied but let me know if Windows doesn’t show them and I will post named screenshots here.
For each variation, you should see how the tone moves towards lighter before the next, darker, bar; or darker before the next, lighter, bar. This is how the edge contrast is enhanced but it is also why overdoing such adjustments can really mess up an image.
The histogram clearly shows the differing tones between the bars with varying “mounds” of intermediate tones.
VC6 and VC7 show the difference between enhancing contrast with the Tone Curve and the Selective Tone tool. If you look carefully, the Tone Curve makes perfectly smooth transitions, whereas the Selective Tone actually adds a slightly augmented contrast edge to the transitions (a sort of sharpening). This is one reason why I try to avoid Selective Tone if possible.
VC8 shows ClearView Plus and just how much it affects the tones in otherwise plain coloured areas. The histogram shows much larger “mounds” of intermediate tones than any of the other contrast options.