I recently ran across this proposal for using a high pass filter in Photoshop to achieve the same results as negative clarity: http://thegreyblog.blogspot.com/2011/11/clarity-adjustment-local-contrast-in.html . In effect, the proposal is to "simply" invert the layer created by the high pass filter and overlay that on the original, this as opposed to not inverting the layer before overlaying it, thereby simulating the clarify filter. I'm having some difficulty doing this in Affinity Photo. I create a high pass live filter underneath the Background layer, set a radius that makes it evident where the local contrast is, and set the blend mode to Overlay. Some details are sharpened, some are not. Now if I invert the filter, nothing is affected unless I paint some areas with white, and then they will be sharpened, which is not negative clarity. I'm sure I'm missing something very elementary here. Can anybody tell me what?