The edge finding method of sharpening

I will have to find time to put everything I have managed to work out about sharpening for digital photography down. But for the moment here is the best fix I have discovered for providing defined edges (sharpness) to a digital image.

Normal an unsharp mask (USM) is fine, but occasionally I need to boost certain areas selectively or there is a degree of noise which gets sharpened destroying the image quality. For these situations I use a filter which used to be called find edges but is actually a high pass filter.

step 1 duplicate your image
step 2 run a High pass filter or equivalent on the duplicate. You should end up with a grey image with the edges defined. Using an option you should be able to define how many pixels this is. Don't go more than 3 if you can help it as higher than this and the prints look odd.
step 3 change the blend mode to either overlay or soft overlay. You can use a hard overlay but I tend to find it looks a bit unreal and sometimes over grainy.
step 4 adjust the opacity to suit your needs
step 5 delete the unwanted areas of sharpness from the duplicate high pass. So for example in a portrait eyes need to be sharp but the outline of the head and body can remain soft. So I would run the eraser over all but the eyes and nose. You can also use this remove noise from the image.

A final note - sharpening is not an excuse for poor focussing. BUT you can rescue the odd image using this method when you didn't quite get it right, PROVIDING you don't intead to make a large print.