I have setup in my Darktable two new presets for Denoise – profiled module as per the description above. For more information on blend modes have a look at Section 3.2.6, “Blending operators”. The “non-local means” instance should be combined with blend mode “lightness” or “HSV lightness” the “wavelet” instance with blend mode “color” or “HSV color”. If needed you can apply two instances of this module (see Section 3.2.4, “Multiple instances”). “non-local means” is a bit better suited to tackle luma (lightness) noise “ wavelet” has its strength in eliminating chroma (color) noise. This module can eliminate noise with two different core algorithms. Quoting from official Darktable documentation talking about Denoise – profiled module: Make sure you watch the video by rawfiner to learn many useful tricks and techniques for denoising in this new version. In December 2018 version 2.6 came out which contains some improvements for Denoise – profiled module. Note that the article was initially written for Darktable 2.4. Intention of this article is to provide some useful pointers in one place. There is also a good thread on dpreview forums. In particular this thread followed by another one. This article was written after some practical advise appeared in darktable-user mailing list. By adding grain we can create an illusion of more detail in the image.
Grain - after applying aggressive noise reduction images often lack detail and can look cartoonish.Dithering - see denoising style from Aurelien Pierre.It is important to adjust parameter Threshold. Sharpen - to help recover detail lost in denoising process.Lowpass - to reduce chroma noise, see denoising styles from William Ferguson and this video.Hot Pixels - with aggressive parameters can help remove outlier pixels.Demosaic - changing parameters can impact especially chroma noise.Some photographers include other modules as part of their noise reduction procedure too: Using them efficiently can feel a bit daunting: Darktable seems to offer a range of modules suitable for the task. Some applications offer one-size-fits-all solutions to keep user choices (and possible confusion) limited. Reducing noise in a photograph can be a complex task. Masterclass on denoising in Darktable 2.6.
Chroma denoising technique using Lowpass module.
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