To elaborate on the BH quote, I might add the words, between 1.5 and 5% depending on resolution. I set my filter at 6%, but I run it while the image is still 3,000 x 3,000. Gabe uses his on the smaller image I think, and runs it at 1.5%. As with all other places, I recommend experimenting within ranges to get a feel that's right for you. Paul