Why does luminance noise get worse after editing, and how can I reduce Darktable denoising artifacts?
Asked 10/29/2018
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When processing RAW files in Darktable, I often see visible luminance noise in darker areas of images shot around ISO 800 and above. After basic edits such as exposure, contrast, and sharpening, the noise becomes much more noticeable. When I apply Darktable’s denoise tools, I can end up with smeared or “painterly” artifacts, while Lightroom seems to preserve detail better on the same kind of image.
Is this mainly caused by my editing workflow, by using the wrong denoise settings in Darktable, or by limitations of the denoising algorithm itself? What Darktable approach works best for reducing both chroma and luminance noise without introducing those artifacts?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
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Many of darktable's algorithms are significantly different from those typically used by other image processing programs. If you cannot get the results you want from darktable, consider trying other raw processing software, such as RawTherapee or UFRaw.
The images are consistent with the use of noise reduction filters with different "strengths", where the darktable filter is much stronger than the one from Lightroom. If there are user-adjustable parameters in darktable, try changing them to reduce the strength of the filter.
Different algorithms detect and treat noise differently. The darktable images have some characteristics that are consistent with median averaging.
Some processing steps, such as increasing contrast and sharpening, are known to increase the appearance of noise. The darktable images appear to at least have had a greater contrast boost than the Lightroom images.
Originally by user75526. Source · Licensed CC BY-SA 4.0
user75526
7y ago
0
Generated from our catalog & community — verify before relying on it.
Noise often becomes more visible after edits like increased exposure, contrast, and sharpening, so part of what you’re seeing is normal. The stronger, smeared look is usually from denoising settings that are too aggressive rather than noise alone.
In Darktable, the result depends heavily on which denoise method and strength you use. Community experience suggests the “painterly” artifacts can happen with profiled denoise when it is pushed too hard. Reduce the denoise strength, and if your version supports it, treat chroma and luma separately rather than trying to remove everything with one strong pass.
A commonly recommended Darktable workflow is:
- use wavelets for chroma/color noise
- use non-local means for luma noise
- blend luma reduction in lightness mode and chroma reduction in color mode
In newer Darktable versions, improved wavelet-based options may be preferred, so check the manual for your version.
If you still can’t get acceptable results, that may reflect differences in the denoising algorithm versus Lightroom. In that case, trying another RAW processor is reasonable.
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AI7y ago
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