Sharpness correction, the illusion

I was editing a set of the beautiful new model Edwige, when I came across one picture I really liked. But there was a problem: it was out of focus. Just not sharp.
To make it worse, it was from a Nikon D800, which means enormous files. And when people first see a photo on the web, they will often see it at 100%, just a little slice of the picture. And viewed like that it will look much more blurry than if viewed so you see the whole picture, especially in a print.

I liked it enough that I wanted to salvage it, so I tried Smart Sharpen in Photoshop.
And it is interesting, unlike what Hollywood would like us to believe, you just can't create details in a photo which weren't there to begin with!!
But: you can create the illusion of sharpness, so to speak. What the Sharpness correction tools do is enhance "accutance", which is the border contrast between two areas. Sort of like it makes little ridges along the borders of parts. This makes a photo seem much sharper without actually calling up any more detail than you already could see.

(Click for big pic.) Before:

After:

Abracadabra.


Update: A. said:

Before the age of Photoshop this effect was used, albeit at the negative film development stage, by using an acutance developer such as "Neofin Blue". This was used with minimal agitation so that the exhausted developer from an area that was being developed as a dark area would form a lighter edge to that area, and the fresh developer covering the lighter areas would develop a darker edge to the lighter areas.
(Simplified explanation.)
Peter R. D.

The ultimate developer with this effect was Agfa Rodinal. It made grain rough, and shadows too dark, but by gawd, it make photos looks *sharp*. It was fantastic. Once I had seen photos like that, I didn't helm until I had found out how he did it.