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Noise reduction artifacts

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#1 crackout

crackout

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Posted 23 September 2021 - 04:14 AM

Hi,

when denoising, sometimes I get these insular artifacts (see left image, source on the right).

Untitled.jpg

(it's an RGB image, but I only displayed the L channel to show the effect more clearly).

The denosing method does not really matter (MMT, MLT, TGV or EZdenoise).

Is there any way to prevent this?

Edited by crackout, 23 September 2021 - 04:59 AM.


#2 Tapio

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Posted 23 September 2021 - 05:58 AM

I really can't see it...
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#3 imtl

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Posted 23 September 2021 - 06:04 AM

I really can't see it...

Same


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#4 crackout

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Posted 23 September 2021 - 06:05 AM

Here's another example (full color this time).

noise.jpg

#5 imtl

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Posted 23 September 2021 - 06:50 AM

You're overdoing the noise reduction. Take it down a bit. Are you using any type of masking?



#6 crackout

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Posted 23 September 2021 - 07:01 AM

Basically, I use an inverted mask from the luminence channel. The linear mask feature in MLT does not work as good.

For the values, I use the following (which are pretty standard):

Untitled.jpg

#7 jonnybravo0311

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Posted 23 September 2021 - 07:51 AM

Take longer integrations and don't use de-noise? :p

 

Joking aside, what you're seeing is the result of PI stretching things harder because there's less noise. This can expose the artifacts of the de-noise process itself. You can tweak the parameters in MLT to try and mitigate or not stretch quite so hard so those artifacts remain buried.


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#8 crackout

crackout

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Posted 23 September 2021 - 08:20 AM

I see those artifacts even at 10h+ integration time.
I do masked stretches that are far below the auto-STF value and still show those artifacts.


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