TODO: proper format for this wikipage
Sharpening with the High Pass:
- Sharpness in 5.25% or more (5.25% seems like the lower threshold for this to work, 10% looks very similar) * Contrast boost in 15% (try other values) * Blending mode in overlay at 100% opacity * Caveat: it messes up with details in the egdes of the histogram (blown up highlights and very dark shadows), but most of the time it's a very good sharpening technique.
The filter creates a mask of the fine detail, sharpness defining how fine that detail is. Then contrast boost defines how much the mask is highlighted (meaning, how much details are highlighted).