I only just found this thread.
I like to apply Physics to what I produce with my camera.
There are a couple of issues that I am not sure have surfaced yet. Distant objects are more subject to the effects of Haze (mostly blue scattering) this reduces actual contrast. Then, there is the JPEG coding that I think has been applied to all of the clips (?) in the thread. This is very non linear and may well be applying smart sharpening to high contrast images more than to low contrast images. The Unsharp Mask in Photoshop does this very effectively on RAW images (no JPEG coding) because you have sliders to determine the parameters for the best result.
Any Lab work needs to take this into account if you want to be sure of your conclusions, I think.
On the subject of Haze; I have looked all over for a filter that would (sharp-) cut out the far end of the visible Blue. This, I am sure, would reduce the worst of the haze - allowing more contrasty pictures - without knocking out all the Blues. Distant mountains can be made to look a lot sharper if you reduce the gain in the blue but this, of course, wrecks the colour balance. I'm convinced that some clever filter could help a lot.
Why isn't there anything about? (or is there?) It could be that filters (other than polarising) are not used much with digital photography because Photoshop can do most of it after the event.