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Słowik inspiruje
Słowik inspiruje
Inspiring
April 7, 2025
Question

Discrepancy Between Global and Masked Blacks Adjustments in Lightroom Classic

  • April 7, 2025
  • 2 replies
  • 346 views

Hello everyone,

I've noticed something puzzling in Lightroom Classic. When I apply a Blacks adjustment of +70 using the Basic panel, the resulting image differs from applying the same +70 adjustment via a mask—even when the mask covers 100% of the image.

From my understanding, Lightroom processes RAW files (often 14-bit) by first converting them into an internal format (likely 16-bit floating-point) and then applying global adjustments before executing any local corrections via masks. This leads me to wonder:

  • Why do these two methods yield different results for the same Blacks adjustment?

  • Is it because the Basic panel adjustments are applied earlier in the processing chain, while masks work on already processed data?

  • Are there any official Adobe documents or technical resources that explain the internal bit-depth handling and processing order which might shed light on this behavior?

I would appreciate insights from Adobe experts or fellow users who have encountered this discrepancy.

Thank you for your time and help!

Best regards,
Paweł Słowik

    2 replies

    Sameer K
    Community Manager
    Sameer KCommunity Manager
    Community Manager
    April 7, 2025

    Okay! You really hit the spot. Here is what I got from the team! 

     

    -Yes, these are implemented a bit differently, even though the global and local controls share the same name.

    -The global Blacks and Whites controls (in the Basic panel in LrC) work a bit earlier in our photo processing pipeline, alongside fundamental controls such as Exposure, Highlights, and Shadows. This is important for ensuring all of the original source data (especially in a raw file) is retained.
    -The masking (local) Blacks and Whites controls are applied towards the end of our photo processing pipeline.  They are really meant to be used for fine-tuning the clipping points of a photo, especially in specific areas.  

    - Please be careful using these: it's very easy to clip areas to pure white or pure black with no detail.  If in doubt, turn on the clipping warning indicators when using these. 

     

    I hope this helps! Thanks!
    Sameer K

      Słowik inspiruje
      Słowik inspirujeAuthor
      Inspiring
      April 8, 2025

      Hey @Sameer K ,

      Following the excellent explanation from You regarding how global and local adjustments in Lightroom are applied at different stages of the processing pipeline, I have a further question:

      When working with local masks, does Lightroom continue to operate on the original RAW data, or are those adjustments applied on data that has already been processed (i.e., after the initial RAW conversion)? In other words, even if a mask covers 100% of the image, is it working on the same “fresh” RAW data as global adjustments, or are we dealing with the processed (likely 16-bit floating-point) data at that point?

      I’m asking because the differences in the results between a global Blacks adjustment and one applied via a mask lead me to wonder if this is solely due to the stage at which the adjustments are applied. Any insights or references to official documentation that elaborate on this processing distinction would be greatly appreciated.

      Thank you in advance for your help!

      Best regards,
      Paweł Słowik

      JohanElzenga
      Community Expert
      JohanElzengaCommunity Expert
      Community Expert
      April 8, 2025

      I'm pretty sure masks are applied to RGB data. Just think about it: how could Lightroom create a sky mask, object mask, or a person mask if this had to be done using mosaiced raw data?...

       

      -- Johan W. Elzenga
      Sameer K
      Community Manager
      Sameer KCommunity Manager
      Community Manager
      April 7, 2025

      Hey, @Słowik inspiruje. Thanks for raising this.

       

      This behavior might be expected with masks and global adjustments, and you're already aware of this. I've shared this with the team for review and comment. 

       

      Thanks!
      Sameer K

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