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jessiefs
Participant
July 11, 2017
Answered

Kevlin scale to -100%-100% scale conversion

  • July 11, 2017
  • 3 replies
  • 34487 views

Does anyone know what Kelvin values convert to on the -100%-100% temperature scale on Lightroom?

I have scrolled through similar discussions but so far none have an adequate answer. What I do know so far though is that:

  • Raw photos being edited in Lightroom will display the kelvin scale, whereas JPGs and TIFFs will display the -100% - 100% scale as the white balance/temperature is set and any adjustments can only be relative.
  • Converting to a DNG file can supposedly help

What I am trying to do is replicate the treatment of an online photo on my own photos (I like the filter), and having found the metadata using the Exif Tool by Phil Harvey, I now know that the colour temperature is 6,300. However, unfortunately I only shot in JPG and as such I am unsure what value to input on my temperature scale that is equivalent to 6,300K. I tried importing as a DNG, as well as exporting as a DNG, but Lightroom only tells me the conversion is not possible for files that are not RAW and keeps my file as a JPG.

Any help would be greatly appreciated

    Correct answer Rikk Flohr_Photography

    The Kelvin scale is only applicable to raw files. In these files, the White Balance hasn't yet been cooked into the file. The degree-value is appropriate to matching (or creating the effect) of light of a specific color.

    When you create a Tiff, JPEG, PSD, PNG, the White Balance has been baked into the file and the full range of color response is no longer possible. Once this happens the degree value in the Kelvin range is no longer applicable. With these files you can adjust them within a limited range that is defined as -100 to +100 in value along the Blue-Yellow and Green-Magenta axes.

    There is no direct conversion because you are really talking about two different things.

    Consider this example:
    If you have a raw file that is set to 6300° and then create a JPEG. 6300 is the center point of both sliders. No adjustment necessary.

    If you have a raw file that is set to 5500° and then create a JPEG. 5500 is the center point of both sliders. Slider adjustment one direction is required to get a similar temperature to the original example.

    If you have a raw file that is set to 8000° and then create a JPEG. 8000 is the center point of both sliders. Slider adjustment the other direction is required to get a similar temperature to the original example.

    3 replies

    TheDigitalDog
    TheDigitalDog
    Inspiring
    October 26, 2020

    Does anyone know what Kelvin values convert to on the -100%-100% temperature scale on Lightroom?

     

    Kelvin defines a pretty large differences in colors as seen below; all software interperpates the colors differently. It isn't at all uncommon to see different values reported from the same raw file in two different products. Bottom line, any CCT values is a range of possible colors:

    Author “Color Management for Photographers" & "Photoshop CC Color Management/pluralsight"
      zwinters
      zwinters
      Participant
      October 26, 2020

      Reviving this question to ask for clarification on a similar issue. Rikk Flohr's answer is excellent. My scenario is a little different. I am working with a RAW file, so my white balance is in kelvin. However, "temp" and "tint" sliders are in X/100 for adjustment brushes, gradients, etc. My question is two parts:

      1) When adjust temp & tint in an adjustment brush or gradient (on a RAW file), is the effect applied an actual white balance adjustment to the affected area, or more akin to the effect applied to a JPG as explained by Rikk above?

      2) If the answer to #1 is "yes, actual white balance adjustment", then how do the two units relate (degrees K versus X/100)?

      Example for how this would be used:

      I wanted to create a cooling effect to a subject's background by adding a warming gel to my flash and cooling the white balance so the subject has a proper white balance and the background becomes "cool". But, say I forgot to gel my flash. If I drop the white balance by 1000K to cool the image, what X/100 value should I use to brush back in the equilivent of 1000K onto my subject?

      Thanks for any insight!

      R
      Community Expert
      richardplondonCommunity Expert
      Community Expert
      October 26, 2020

      Temp and tint within the brush / gradient tool sliders, even when you are editing from a Raw file, operate as a purely relative adjustment. The same as within the Basic panel when editing from a processed bitmap file.

       

      AFAICT the local adjustments deliver a "pre-influenced" image to the Basic panel global adjustments, and then the results from Basic are further modified by such tools as Tone Curve, Split Toning / Grading. These dependencies can be empirically shown. A -50 (unitless) local Temp adjustment should deliver the same visual magnitude of change, across different cases and between Raw and non-Raw - but this change may not always equate to the same number of degrees K. Because this is likely not linear. Also degrees K seldom match exactly between as-shot WB from the camera, and how LR implements WB corrections internally, or how other converter programs do so. It can be thought of as a rough indicator rather than a tightly comparable measure.

        Rikk Flohr_Photography
        Community Manager
        Rikk Flohr_PhotographyCommunity ManagerCorrect answer
        July 11, 2017

        The Kelvin scale is only applicable to raw files. In these files, the White Balance hasn't yet been cooked into the file. The degree-value is appropriate to matching (or creating the effect) of light of a specific color.

        When you create a Tiff, JPEG, PSD, PNG, the White Balance has been baked into the file and the full range of color response is no longer possible. Once this happens the degree value in the Kelvin range is no longer applicable. With these files you can adjust them within a limited range that is defined as -100 to +100 in value along the Blue-Yellow and Green-Magenta axes.

        There is no direct conversion because you are really talking about two different things.

        Consider this example:
        If you have a raw file that is set to 6300° and then create a JPEG. 6300 is the center point of both sliders. No adjustment necessary.

        If you have a raw file that is set to 5500° and then create a JPEG. 5500 is the center point of both sliders. Slider adjustment one direction is required to get a similar temperature to the original example.

        If you have a raw file that is set to 8000° and then create a JPEG. 8000 is the center point of both sliders. Slider adjustment the other direction is required to get a similar temperature to the original example.

        Rikk Flohr: Adobe Photography Org
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