Can I keep my gamma curve when I create a LUT?

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  • #6272

    RIppolito
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    Prior to obtaining my eecolor LUT box, I had calibrated my OLED.  The grayscale was very good.  I had set the gamma to a nominal 2.3, but went lower down at 5 and 10 IRE, in order to come out of black more quickly.

    Is there a way that I can build a 3D LUT that preserves this gamma?   I’d like to keep that gamma curve, and use the LUT to address the inaccuracies in the color space (which is does very well, by the way).

    Thank you in advance…

    Ron

    #6275

    Florian Höch
    Administrator
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    Is there a way that I can build a 3D LUT that preserves this gamma?

    BT.1886 will achieve something similar provided that the black level is not zero (this being an OLED, you may have to raise black a little. If you don’t want to do that, you can also create a synthetic Rec. 709 profile to use as source for the standalone 3D LUT maker). Select “custom” as tone curve on the 3D LUT tab. Change gamma to 2.3 “relative” and change output offset to around 95%. You may need to play around with the output offset a little.

    #6281

    RIppolito
    Participant
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    Thanks for the tip, Florian.  I read the descriptions of ‘absolute’ and ‘relative’ for that setting, but I was a little unclear.  What are you doing when you scale the input, versus scaling the output?  How does varying the offset affect the calculation?  Lastly, what is the 50% referring to?

    Ron

    PS – overall, the documentation is terrific, perhaps the best I’ve seen

    #6283

    Florian Höch
    Administrator
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    What are you doing when you scale the input, versus scaling the output?

    A picture may help to illustrate:

    PS – overall, the documentation is terrific, perhaps the best I’ve seen

    Thanks 🙂

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    #6285

    RIppolito
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    From your diagrams, it appears that 100% output offset comes out of black more quickly, which is what I’d want to see.

    Can I make another 3D LUT simply by making that selection change, and re-running?  In other words, I don’t have to re-sample the display, do I?

    There is another checkbox in the 3D LUT tab that says ‘include the calibration’.  What impact does that have on the LUT?  What will you use to construct the LUT if this box is not checked (what is left out)?

    Thanks again…

    Ron

    #6286

    Florian Höch
    Administrator
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    From your diagrams, it appears that 100% output offset comes out of black more quickly, which is what I’d want to see.

    No, the other way around, input offset comes out of black quicker. It’s probably easier to see when flipping between the two images:

    Can I make another 3D LUT simply by making that selection change, and re-running? In other words, I don’t have to re-sample the display, do I?

    Correct. Just untick “Create 3D LUT after profiling”.

    There is another checkbox in the 3D LUT tab that says ‘include the calibration’. What impact does that have on the LUT? What will you use to construct the LUT if this box is not checked (what is left out)?

    If you have used 1D calibration (tone curve on the calibration tab anything else than “As measured”), it needs to be applied for the 3D LUT to be correct.

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