Call to advice for fighting color noise

Hi everyone!

With my new Sony a5000 camera I stumbled upon a little more color noise that I experienced before. Mostly magenta/purple noise, like here on the screenshot


For removing color noise I usually use a lowpass module with a ‘color’ blending, but does not help much now. is there another method for doing that?

and another question… regardles of lens why, unlike of other color, the purple noise is so pronounced?
provided that I’m using custom camera input profile within Adobe gamut, highlights reconstruction and having finetuned demosaicing settings for the best result. Any thoughts?

First, I’d try not pixel peeping at 200%. Even the best sensors at base ISO are going to have some noise at that level unless you apply some noise reduction.

If possible, can you post an example RAW file? The lowpass module with color blending is extremely good at removing color noise in my experience, but I only use it for really noisy photos. For low ISO images, the default profiled denoise is also good enough as a one-click solution if your camera is one of those supported.

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I usually use profiled denoise since my camera is supported. Works pretty good for me

instance 0; wavelet; 100%; strength 1; on the color
instance 1; wavelet; 50%; strength 1; on the lightness
instance 2; non-local means; 50%; strength 1; on the averaging

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Oh, wow fighting noise on multiple levels - that’s interesting and looks promising!
As soon as DT devs add support of cameras from RPU , I’d be able to try that too. thanks for advice!

So far, I use Lowpass with color blending, adjusting the radius per noise size (sometimes it’s different). I see that sensors are susceptible to low temperatures making the noise more pronounced.

That is not really how it works. The RPU samples are used for regression testing of rawspeed library.
For the camera support, one needs to open a new camera support issue. Just uploading samples to the RPU, while is immensely helpful, is not enough to get the camera supported.

That being said, please do keep submitting samples to RPU, there are still a lot of missing samples.
All new Samsung’s (NX3000+) are missing.

Thanks, Roman. Will comply as instructed.

Here is an example (zoom 100%):
Original:


instance 0; wavelet; 100%; strength 1; on the color:

first one plus
instance 1; wavelet; 50%; strength 1; on the lightness:

first two plus
instance 2; non-local means; 50%; strength 1; on the averaging:

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Uhmmmmm! The result is lovely! Where did you learn to do that? :slight_smile:

Here: https://youtu.be/4nBzAeM0tpI I think the author of the video found the info in the searchable email archive: https://www.mail-archive.com/darktable-dev@lists.darktable.org/

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RAW of that particular picture I sent you the cropped area of as well as its darktable XMP file are posted here:

You can play with the denoise profiled instances and see how they work.

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Really nice results, I have a new noise reduction preset :slight_smile:

@Andrius Tried your method today and the results are amazing, even though I had no dedicated camera profile and used generic poissonian preset instead. Excuse the hastily applied mask to focus on the sky, but the results speak for themself!!!

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@mosaster I am glad it worked for you.
I wish I could take a credit for this but I just copied somebody’s method.
I guess darktable devs have done a great job :slight_smile:

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To smoothen out, I like to put an instance on top of the stack using average blending, which just gives it the final touch.

…aaaand of course, YMMV. :slight_smile:

I saved the three instances as a darktable style and uploaded it here:
https://redmine.darktable.org/attachments/download/3411/denoise%20profiled%20stack.dtstyle

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Wow, that worked great for me // saved them as presets // used them on other images that I was having trouble with and so far, really good results.

Thanks for the NR presets. I’d modify them according to what houz suggests in this text:
“For profiled denoising better use ‘HSV color’ instead of ‘color’ and ‘HSV lightness’ instead of ‘lightness’”.

Thank you for the comment.
I followed the link and finally got here:
http://darktable.org/usermanual/ch03s02s06.html.php

I am wondering what “clamping” is

@Andrius See https://en.wikipedia.org/wiki/Clamping_(graphics)

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Thank you afre