While postprocessing my photos in GIMP, I'm rarely satisfied of the results of the sharpening. Often I find it excessive, giving to the image the look of an ordinary post card. So, I'm still looking for the optimal settings
This afternoon, trying to learn more on sharpening techniques, I've found on the GIMP User Manual the following tip:
Sometimes using Unsharp Mask can cause color distortion where there are strong contrasts in an image. When this happens, you can often get better results by decomposing the image into separate Hue-Saturation-Value (HSV) layers, and running Unsharp Mask on the Value layer only, then recomposing.
Does anybody knows more about this approach?
I made a test on an image applying the traditional Unsharp Mask and then Unsharp Mask on Value channel only. I intentionally exagerated the sharpening settings in order to more easily evaluate the differences.
Here the results: do you notice any significant difference or improvement?
#1 No sharpening
#2 Unsharp mask (Settings: Radius=3 pixels, Amount=0.40, Threshold=20)
#3 Unsharp mask on value channel (same settings as #2)