I’ve been using both GIMP and Rawtherapee (RT) to develop photos. Sharpening seems to almost always be useful. However, while both programs support the unsharp mask method (USM) and use the same terminology for describing the controlling parameters there is no similarity in the values specified for said parameters. For example, they both use Radius where GIMP defaults to 3 and RT to .5. Then both have Threshold where GIMP defaults to 0 but RT has a set consisting of 20, 80, 1200 and 2000. Last they both accept a value for Amount where GIMP defaults to .5 and RT to 200. I tend to leave Threshold alone and fiddle with Radius and Amount.
It seems like there ought to be some relationship between the controlling parameters. For example, how do the values in one program relate to the other? It seems like it should be possible to understand a equivalence relationship between the values being used by each program.
Might someone be able to either shed some light on this discrepancy between GIMP and RT? Maybe reference some documentation that explains well enough to figure this out.