What is the meaning of blurradius and radius in Sharpening?

Software darktable
1

Why there are two gaussianBlur in the process of sharpening (USM)? What is the meaning of blurradius and radius?

2

Why there is another USM/gaussianBlur before the main USM process/

3

Hi @zengyuxi, and welcome!

Sorry, I do not understand your question.
Could you please take a screen dump?

Operating system?
Version of darktable?

Have fun!
Claes in Lund, Sweden

4

I see radius, amount and threshold (the usual controls), no ‘blurradius’.
image

Or do you mean diffuse or sharpen? That’s a complex module. I suggest you read the documentation and watch videos on YouTube.

5

The Wikipedia article on unsharp masking explains these parameters, independent of the software you use.

Hermann-Josef

6

There is also a “blurring radius” in the pane for the drawn/parametric masking. But that one has nothing to do with the unsharp masking itself.
It blurs the defined mask only, to soften the transition between masked (which will show the effect of the module, USM in this case) and unmasked areas.

1 Like
7

If, as suggested by @rvietor , you are looking at the _masking_parameters:
image

then read here:
https://docs.darktable.org/usermanual/4.0/en/darkroom/masking-and-blending/masks/refinement-controls/

There’s an old release notes page here. The interface has changed, but you’ll recognise it:
darktable 2.6 | darktable. Search the page for Edge-aware bluring for blend masks.

1 Like