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PvlKnn
Participating Frequently
June 6, 2024

P: Thick red/blue banding in brightened shadows of Denoised DNGs

  • June 6, 2024
  • 33 replies
  • 7322 views

I noticed this a few days ago but didn't realize the scale of the issue until I played around with the Exposure values and tested them to the limit.

 

I've attached two screenshots of the Develop module. The control image is an RAF photo with Exposure boosted to +5. The experiment is a DNG derived from the RAF, with a Denoise amount of 30. The effect manifests at all amounts from 1 to 100. However, the banding is not present in the Enhance Preview window. I have also attached the original Fujifilm RAF from my X-H2s camera (lossless compressed) and an affected DNG with Denoise.

 

I can't detect this phenomenon in NR conversions before LrC 13.3. 

 

The significance should be self-evident. The banding artifacts appear in images with lifted shadows or underexposed photos with boosted brightness.

 

Lightroom Classic version: 13.3.1 [ 202405311538-6d7c0308 ]
License: Creative Cloud
Language setting: en-CA
Operating system: Mac OS 14
Version: 14.5.0 [23F79]
Application architecture: arm64
Logical processor count: 12
Processor speed: NA
SqLite Version: 3.36.0
Power Source: Plugged In, 80%
Built-in memory: 32,768.0 MB
Dedicated GPU memory used by Lightroom: 5,764.7MB / 21,845.3MB (26%)
Real memory available to Lightroom: 32,768.0 MB
Real memory used by Lightroom: 3,716.8 MB (11.3%)
Virtual memory used by Lightroom: 424,322.1 MB
Memory cache size: 1,238.0MB
Internal Camera Raw version: 16.3.1 [ 1889 ]
Maximum thread count used by Camera Raw: 5
Camera Raw SIMD optimization: SSE2
Camera Raw virtual memory: 2281MB / 16383MB (13%)
Camera Raw real memory: 2285MB / 32768MB (6%)

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    PvlKnnAuthor
    Participating Frequently
    June 7, 2024

    Sorry for missing the raw files that were omitted from the attachment. You can download the original Fujifilm RAF and corresponding DNG (Denoise amount 30) from my OneDrive: 

    https://1drv.ms/f/s!AjAOXAIjC1XCgaMEHGfxMYIMFnHMnw?e=lzb5o4

    Ian Lyons
    Community Expert
    Ian LyonsCommunity Expert
    Community Expert
    June 7, 2024

    I downloaded your two files. and imported them both into a copy of LrC 13.2 and 13.3.1

     

    When I ran denoise on the RAF file in LrC 13.2 I get a large purple block in the darker regions of the image. However, when I denoise the RAF file in 13.3.1 I get a grid of large purple and orange squares in the darker regions. Therefore, since both versions are producing the coloured blocks, albeit of different size and pattern, my original theory of the Apple Neural Engine being a possible cause is in doubt.

     

    As a further test, I increased the exposure of the RAF file by 5 stops plus Shadows of 100%. After doing so, the darker areas have a heavy yellowish tinge.  At this point I'm inclined to say that rather than a bug,  the results obtained from denoise are being heavily influened by the underlying colour tinged areas in the original RAF file. 

     

    Maybe @johnrellis can run a test using Windows to see if he produces similar results to mine.

     

    I've attached a screenshot of denoised version from LrC 13.2 and 13.3.1.

     

     

    P
    PvlKnnAuthor
    Participating Frequently
    June 7, 2024

    We can call it a bug or a result of how Denoise interprets the underlined colour in the deepest shadows, but the fact remains: in the deepest shadows, Denoise is generating colour patterns that are not present in the source raw file. It's not even doing it consistently across different computers, to boot. 

     

    To ensure this wasn't caused by some aspect of the lights in the scene (doubtful), I Denoised and pushed a photo from months ago of a different location. Further, to ensure this wasn't some aspect of my camera or artificial lights, I repeated the process on a photo from last year taken with a different Fujifilm (X-T2 vs X-H2s) camera. The results are identical—bluish-reddish vertical banding in the deep shadows (not checkerboard like in your results).

      

     

     

    The new and old files are here:

    https://1drv.ms/f/s!AjAOXAIjC1XCgaMA235qbZFycHrnZA?e=ct6D9y

     

    Ian Lyons
    Community Expert
    Ian LyonsCommunity Expert
    Community Expert
    June 6, 2024

    Your System Info indicates that you're using an Apple Silicon based Mac. LrC 13.3 was the first version to use the Apple Neural Engine, which is feature of Apple Silicon. This 'may' explain why the issue wasn't present in earlier versions. I'm not aware of any other changes to Denoise. 

     

    Please, upload the original raw as @johnrellis requested. 

      johnrellis
      johnrellis
      Legend
      June 6, 2024

      The original raw didn't make it as an attachment. Upload it to Dropbox, Google Drive, or similar and post the sharing link here. Adobe likely won't pay attention without being able to reproduce the issue.

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