Dark Strokes Filter not working

CC 2015. My Dark Strokes Filter has stopped working properly. Specifically the black intensity slider doesn't do anything at all no matter where you put it. The white intensity filter actually still works. At first I thought it was minor highlights I was putting in the painting I was working on that was throwing it off but then it stopped working properly for an image I had used it on earlier. The black intensity is loaded at a default of 9/10 and the white at 5/10. Resetting the preferences doesn't seem to do anything including not affecting these defaults. This is a png file