Reference: the argument behind each control
The passes on this site show you every number they are using. A number with no model behind it is only a guess with decimal places, so the models are written down here rather than compressed into tooltip text nobody can argue with.
Written so far
Two pages, both long, both about a decision that is usually made by dragging something until it looks right. They are written to be read away from the instrument — from a search about a result somebody already got in another program — so each one restates the mechanism before it argues about it. Neither is a walkthrough of this site.
Amount, radius and threshold: the three controls, in full
Each parameter taken to both ends of its range, what the picture does there, and four worked starting sets — portrait, landscape, product, document scan.
Settles: Why turning one control up can cancel what another one was doing.
What deconvolution can and cannot recover from a photograph
The straight-line motion model stated plainly, the six ways a real photograph violates it, and the three checks that separate recovered detail from detail the solver made up.
Settles: Whether the frame in front of you is inside the domain at all.
What is deliberately not here
Two subjects that belong in this list are argued on the routes themselves instead, because in both cases the argument is inseparable from a control you need in front of you. Output sharpening — why a setting that looks correct on a monitor is too weak for matte paper, and roughly how much too weak — sits with the export presets, where the destination is being chosen. The balance between removing noise and raising acutance sits with the measured noise figure, because the whole point is that the figure decides the setting.
Nothing here covers exposure, colour, faces, enlargement or file size. Those are separate problems with their own failure modes; this site works on one dimension of picture quality and the reference shelf is the same width as the instrument.
Where to apply any of it
The three parameters live in step three of the sharpening steps. The motion solver and its two estimators are on the deblur route, and the large-radius passes are on the local-contrast route. Every figure quoted in either page can be typed into one of them and checked at 100% against a photograph of your own.