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sai krishnam80741157
Participant
June 26, 2017
解決済み

Whats the meaning of "LR manages color is Prophoto RGB" when my monitor is only capable of sRGB?

  • June 26, 2017
  • 返信数 1.
  • 659 ビュー

I'm a newbie and am fundamentally confused how a software tool like LR can work in its own color space independent of monitor capabilities!

Basically, I have an sRGB monitor and printer, both of whose gamut is smaller than prophoto. Since by definition it's not a WYSIWYG setup (i.e. LR on prophoto vs others on sRGB), I'm bothered about:

1.  How can I trust my painful hours of editing would produce EXACT colors at a printer (also calibrated to sRGB)?

The answer cannot be soft proofing, right? I need LR to be able to work in sRGB (because my monitor is only capable of it) in REAL TIME  so that I can be assured any edit i do will show up in my prints exactly like I see on my monitor. i do not want to waste countless hours in "develop" just to learn the moment I go to soft proofing, results could be subtly different, and i can't tell or track where what's happening.

2. Even more importantly, is there only color truncation (i.e. only highly saturated colors are lost as prophoto to sRGB conversion happens in real time) or complete loss of color data?

Any clarifications are highly appreciated. Given LR has been around for so long, I believe this is a non-issue, and am curious to know the answer.

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Rob_Cullen
Community Expert
Rob_CullenCommunity Expert解決！
Community Expert
June 26, 2017

The answer to this question is so 'deep', and I cannot swim, so can only refer-

http://www.adobe.com/digitalimag/pdfs/phscs2ip_colspace.pdf

Digital Dog :: Main

Working Space Comparison: sRGB vs. Adobe RGB 1998

https://www.apnphotographyschool.com/concepts/color-management-mythbuster-facts-myths-about-color-spaces-and-color-profi…

Regards. My System: Windows-11, Lightroom-Classic 15.1.1, Photoshop 27.3.1, ACR 18.1.1, Lightroom 9.0, Lr-iOS 10.4.0, Bridge 16.0.2 .
S
sai krishnam80741157作成者
Participant
June 30, 2017

I may have found the answer here (see "6. Why use ProPhoto RGB when the monitor cannot display it").

The answer seems to lie in the fact that the higher to lower gamut conversion is lossless, i.e. somehow as image is painted on to monitor, LR in REAL TIME converts prophotoRGB colors into sRGB space losslessly. I can imagine, this is a simple calculation - let's say the R-channel value is x in prophotoRGB, it'll be x*maxColorInsRGB/maxColorInProPhotoRGB. However, the trick is to do it actively in real time.

NOTE: HUGE thanks to wobertc. The articles are simply amazing and have been answering so many fundamental questions that always bothered me. Appreciate!

    D Fosse
    Community Expert
    D FosseCommunity Expert
    Community Expert
    July 1, 2017

    It's not as complicated as you think.

    The file is held in linear ProPhoto throughout. The original file is never modified for the monitor. The substream of data that are sent to the video card and monitor are converted, remapped, into the monitor color space, using your monitor profile.

    This is indeed a very lossy conversion. All the colors that are out of the monitor's gamut are mercilessly clipped and lost. What remains is remapped to preserve color appearance.

    If you're using Photoshop you'll be familiar with profile conversions and how they work. This is the same thing, performed, as you say, in real time.

    The point is that the file itself is never affected by any of this. It knows nothing of what goes on downstream. It lives happily in linear ProPhoto the whole time.

    The reasons for using these large color spaces have nothing to do with the monitor. It's to give editing headroom while working, without the risk of prematurely clipping saturated colors. Of course, for final output you'll need to squeeze it into these smaller output color spaces. You can either accept any clipping that occurs, or you can do your own remapping to fit the data into the destination color space.

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