So, in that “other” forum a new member asked a question in reference to my books; The Digital Negative & Print about local sharpening. He correctly said that the local control adds or subtracts sharpening “Amount” based on the Detail panel settings. His question was what happens when the Amount slider is set to zero? I was pretty sure of the answer but pinged Eric Chan, an ACR engineer, about the question. His answer was pretty much what I expected…
When the Amount slider in the Detail panel is set to zero, adding Sharpening from the local controls will add sharpening amount with the Radius and Detail settings at default; Radius of 1.0 and a Detail settings of 25. That’s pretty easy to see in ACR & LR.
However, if you set the Amount slider in the Detail panel to zero and paint minus (negative) Sharpness amounts, both ACR & Lightroom doesn’t do anything at -1 thru -50, it’s an odd dead zone where the settings don’t do anything other than make the mask.
If you set the Sharpness setting to a -51 thru -100, you will actually add a Lens Blur effect.
That’s what Eric said…but I’m not 100% sure that’s completely true.
EDIT: Actually, I was curious to prove Eric either right or wrong because I thought I was seeings a real subtle difference, so I had to test it. I built multiple sh=napshots in LR with local sharpening set to zero, -25, -49 and -50 & -51 and opening them in layers in Photoshop. I set the zero sharpening as the bottom layer and put the other layers above. I set the layer blend to Difference. There was NO DIFFERENCE between the zero, -25, -49 and -50 layers. There was a very subtle difference in the -51 layer which confirmed the addition of the lens blur. So, Eric was, of course correct.
I had a friend ping me that somebody on that other forum referenced me and my books but I don’t post on that other forum and only visit when somebody tells me there’s something I might want to see.
Maybe that guy will come visit this forum and find the answer here. 😎
This topic was modified 6 hours, 36 minutes ago by Jeff Schewe. Reason: Confirmation of findings after testing