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B__R
Participant
January 16, 2012
Question

Color Management in Lightroom 4

  • January 16, 2012
  • 1 reply
  • 13511 views

By default, Lightroom uses the Pro Photo color space "with the same gamma curve as sRGB," according to something I read somewhere. Now Pro Photo is a very wide color space, wider than any monitor can display - even my wide-gamut (Adobe RGB) monitor. If I adjust the color in an image to very high saturation, then at some point in the adjustment I must reach a part of Pro Photo that cannot be displayed on my monitor so I would expect to stop seeing any changes after that point. Yet I continue to see changes all the way up to saturation 100. So this has something to do with the sRGB curve that is somehow mapping those out-of-gamut colors to something that can be displayed.

I'd appreciate some explanation of this process, or any useful links.

Thanks.

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    1 reply

    TheDigitalDog
    TheDigitalDog
    Inspiring
    January 16, 2012

    LR and ACR process data with ProPhoto primaries and a linear (TRC 1.0 gamma) encoding. The histogram and RGB percentage values use a 2.2 TRC (Melissa RGB).

    In terms of the disconnect between the display gamut limit and the editing space, not much you can do. If you are editing by moving a slider and all of a sudden you stop seeing the edit affect the preview, back off, you are probably editing colors outside display gamut. Also keep in mind, there are ‘colors’ defined in ProPhoto RGB that are not visible (and technically can’t be called colors).

    Author “Color Management for Photographers" & "Photoshop CC Color Management/pluralsight"
    B
    B__RAuthor
    Participant
    January 17, 2012

    Thanks for the reply. The thing is I don't necessarily stop seeing the edit affect the preview. Here's an experiment I did - I imported a raw (Adobe RGB tagged) image of grass into LR. Recall that I have a monitor that basically covers all of Adobe RGB. I notice that as I move the saturation slider I can see changes in the green, including between saturation values from 50 to 100. If I soft-proof the image using the Adobe RGB profile, it indicates that basically the whole image is out-of-gamut already at a saturation value of 50. Yet I can continue to change the saturation beyond 50 with noticeable results.

    I'm coming to the conclusion that LR continues to map the out-of-gamut colors down to Adobe RGB, using some particular rendering intent (Perceptual?). As the colors get more and more out-of-gamut, the mapping changes so the image changes. Make sense?

    Tai_Lao
    Tai_Lao
    Inspiring
    January 17, 2012

    I'm not a Lightroom user, but…

    B__R wrote:

    …I imported a raw (Adobe RGB tagged) image of grass into LR…

    That sounds like an oxymoron.  If the image is truly raw, it has no color profile embedded, and cannot be "tagged".

    ____________

    Wo Tai Lao Le

    我太老了

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