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Color management

Jun 25, 2012 12:34 PM

 
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  • Victoria Bampton
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    Jun 25, 2012 12:38 PM   in reply to Community Help

    Documentation correction.  "Unless you choose differently in the Soft Proofing panel, the Develop module also displays photos in the Adobe RGB color space."  is wrong.  Develop uses a larger color space with ProPhotoRGB primaries.  AdobeRGB is used for pre-rendered previews in other modules.

     
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  • Currently Being Moderated
    Jun 25, 2012 5:04 PM   in reply to Victoria Bampton

    Victoria is correct. The help documentation is incorrect. The Develop module uses ProPhotoRGB.

     
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    Nov 3, 2012 9:10 PM   in reply to Community Help

    When working in a RAW/DNG workflow, does Lightroom retain the original photo's color data until its exported to a file or printer?   In other words, when working with a RAW/DNG is there only a single color mapping taking place (upon export/print)?

     
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  • Victoria Bampton
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    Nov 4, 2012 12:36 AM   in reply to D Ward (CA)

    D Ward (CA) wrote:

     

    When working in a RAW/DNG workflow, does Lightroom retain the original photo's color data until its exported to a file or printer?

     

    Yes

     
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  • Andrew Rodney
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    Nov 5, 2012 7:26 AM   in reply to D Ward (CA)

    A raw file really has no defined color space. It's essentially Grayscale data until it is rendered into some RGB color space, at which point it can be encodded into a defined color space. A DNG might contain raw data, might not. So this is a bit more sticky to answer.

     

    If you want to go deeper, we can talk about the assumption all raw converters first make about the Grayscale data, then what they do to end up with data that can be processed using that converters native color space for processing (in LR and ACR that's ProPhoto primaries but a different gamma encoding). And a lot of this processing is so proprietary that we can only guess on certain details. But the important thing to consider is that if you ask LR to give you ProPhoto RGB, that's not what the raw data was initially.

     
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    Feb 16, 2013 9:51 AM   in reply to Victoria Bampton

    Er... No, that is actually incorrect, and the documentation is perfectly right.

     

    When you enter Soft Proofing mode in Develop screen (by hitting "S" or through "View ->  Soft Proofing -> Show Proof" menu), the default color space for proofing is indeed "Adobe RGB (1998)". In Soft Proofing It will be shown on the right, under the histogram. In fact, by default you will only have to Soft Proofing color spaces to choose from "sRGB" and "Adobe RGB (1998)". "ProPhotoRGB" is not even an option.

     

    "ProPhotoRGB" is the default "working" color space for Develop output, that is true. However, the documentation is talking about Soft Proofing, which is a completely different thing.

     
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    Feb 16, 2013 10:02 AM   in reply to Andrey Tarasevich

    Now I see that they thoughtlessly updated the text above to "ProPhotoRGB", thus making it incorrect

     
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  • Victoria Bampton
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    Feb 16, 2013 12:44 PM   in reply to Andrey Tarasevich

    The documentation is talking about colour management in general.  "Unless you choose differently in the Soft Proofing panel, the Develop module displays photos in the ProPhotoRGB color space." is one of those wonderful sentences that could be read in multiple ways.

     

    What they were trying to say was "Unless you turn on Soft Proofing and choose a different profile, the Develop module displays photos in the ProPhotoRGB color space."

     
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    Feb 16, 2013 1:11 PM   in reply to Andrey Tarasevich

    The Library module stores all previews in the AdobeRGB color space. These previews are also used when printing in draft mode. Unless you choose differently in the Soft Proofing panel, the Develop module displays photos in the ProPhotoRGB color space.

     

    I agree it would clearer if written as follows:

     

    "The Library module stores and displays all previews in the AdobeRGB color space. These previews are also used when printing in draft mode. The Develop module displays photos in the ProPhotoRGB color space, except if you choose differently using the Soft Proofing panel."

     
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    Feb 16, 2013 1:27 PM   in reply to Victoria Bampton

    I still don't understand what you mean by this. Specifically, what does "displays photos in the ProPhotoRGB color space" mean? How do you display some photo in a specific color space?

     

    It does make sense within the concept of Soft Proofing, where we do actually attempt to display what would happen to a photo if we converted to to a specific color space/profile. The Soft Proofing feature is targeted, of course, at device-specific color spaces/profiles, like monitor or printer profiles. I.e. the purpose of Soft Proofing is to simulate (as closely as possible) how the photo will look on that physical device. This is why the only options we get there are sRGB, Adobe RGB and (optionally) installed printer profile - there are devices out there that natively support these color spaces. ProPhotoRGB is not a popular color space for physical devices, to put it mildly, which is why it is not even included into the set of Soft Proofing profiles.

     

    Now, as for normal photo display in Develop mode, I don't immediately see what "displays photos in the ProPhotoRGB color space" can possibly mean. The LR will read the image file in whatever internal color space it was stored. It can be sRGB, Adobe RGB, ProPhotoRGB or BobFromAccountingCMY. It will transform the data from the image's color space to the color space of your monitor and use it to display the photo. I.e. the photo is always displayed in your monitor's color space. I don't see where in this chain ProPhotoRGB comes into play as something different from any other color space.

     

    The only place where ProPhotoRGB is given preferntial treatment is that LR4 uses this color space as the defualt color space for export and, probably, as color space for internal representations (is the latter true?). Neither has much to do with "displaying" photos, which is why I'm puzzled by that statement.

     
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  • Andrew Rodney
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    Feb 16, 2013 3:22 PM   in reply to Andrey Tarasevich

    Andrey Tarasevich wrote:

     

    I still don't understand what you mean by this. Specifically, what does "displays photos in the ProPhotoRGB color space" mean? How do you display some photo in a specific color space?

    The Histogram and numbers when not soft proofing are in MelissaRGB which is like ProPhoto RGB. It uses the same RGB primaries but instead of a 1.8 Tone Response Curve it uses a sRGB like 2.2 TRC.

     

    The previews in Develop should be in Adobe RGB (1998) unless something has changed I'm unaware of. This is for previewing nothing more (well you can send this out as Draft print).

     

    When you are not soft proofing, you're therefore viewing an Adobe RGB preview with MelissaRGB numbers while LR is using neither when processing the data. ALL these previews depend on the quality of the display calibration and the profile that describes that behavior.

     
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    Feb 16, 2013 3:36 PM   in reply to Andrey Tarasevich

    I agree "displays photos in ProPhotoRGB color space" is a bit vague.  Here's what I believe to happen (ignoring soft proofing):

     

    In Develop Module, the image is converted from raw (or whatever is the format of the image) to ProPhoto RGB.  This conversion always takes place when an image is worked on in Develop Module.  ProPhoto is Lightroom's working space, and it can't be changed.  Assuming the monitor has a correct profile, the image is mapped from ProPhoto RGB to monitor colour space for display. 

     

    In Library Module, Lightroom displays the preview image.  If there isn't a preview, it creates one.  Previews are stored in Adobe RGB colour space (in jpeg files).  When the image is displayed, obviously Lightroom maps the image to the monitor colour space, but this time from Adobe RGB. 

     

    I stand to be corrected by an Adobe insider, but this is what appears to happen. 

     

    Edit: I overlapped with Andrew, but I think we're saying compatible things.

     
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  • Andrew Rodney
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    Feb 16, 2013 5:08 PM   in reply to CSS Simon

    CSS Simon wrote:

    ProPhoto is Lightroom's working space, and it can't be changed. 

    Pretty close. The processing is done again with ProPhoto primaries but with a linear 1.0 TRC so we can't call it ProPhoto RGB any more than we can call MelissaRGB ProPhoto RGB. The only place we 'get' ProPhoto in LR is if we export specifically to that color space and in LR 4 we can now soft proof and thus update the numbers to ProPhoto RGB.

     
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  • Victoria Bampton
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    Feb 17, 2013 1:03 AM   in reply to CSS Simon

    Yes, the word 'displays' is confusing matters.  We're all rather going in circles here, so let's come back to the original statement, which Simon Chen (LR engineer) agreed.  "Develop uses a larger color space with ProPhotoRGB primaries.  AdobeRGB is used for pre-rendered previews in other modules."

     

    So for the sake of complete clarity, let's summarize this way:

     

    Pre-rendered previews used in Library module and elsewhere are stored in AdobeRGB.

     

    Develop module converts data on the fly.  Internally it uses a larger color space with ProPhotoRGB primaries and a linear tone curve.  The Develop histogram and numeric readouts are based on this large color space unless you choose a profile for soft-proofing.

     

    Does that work for everyone?

     
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  • Andrew Rodney
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    Feb 17, 2013 9:30 AM   in reply to Victoria Bampton

    Victoria Bampton wrote:

    The Develop histogram and numeric readouts are based on this large color space unless you choose a profile for soft-proofing.

    Based on this color space but with a 2.2 TRC. The primaries are the big deal here but one could toggle between say a ProPhoto primary with 1.0, 2.2 and the actual TRC of ProPhoto (1.8) and the differences in the Histogram would be small. You could in theory build MelissaRGB and the unnamed internal color space in Photoshop for access in the soft proof module in LR. The 2.2 (MelissaRGB) profile would use a simplified tone curve so it's not 100% identical to the 2.2 TRC LR uses. Yes, it's all rather confusing and probably not necessary for 95%+ of LR users to worry about.

     
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  • Currently Being Moderated
    Feb 17, 2013 3:52 PM   in reply to Andrew Rodney

    The DIgital Dog knows of what he speaks–Let sleeping dogs lie!

     
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  • Currently Being Moderated
    Apr 10, 2013 9:56 AM   in reply to Community Help

    I can understand the need to specify the color space when soft proofing.  However, I spent some extra dollars to get a monitor than can display the Adobe RGB color space, but when I'm in the Develop Module the working space seems to be ProPhoto which has a much wider gamut than my monitor can display.  LR must fit the colors into the gamut that can be displayed on my monitor so that I can see correctly what the effect is of my color editing. How does LR know the gamut of colors that can be displayed on a user's monitor? 

     
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  • Andrew Rodney
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    Apr 10, 2013 10:01 AM   in reply to image_gsam

    image_gsam wrote:

    when I'm in the Develop Module the working space seems to be ProPhoto which has a much wider gamut than my monitor can display.  LR must fit the colors into the gamut that can be displayed on my monitor so that I can see correctly what the effect is of my color editing. How does LR know the gamut of colors that can be displayed on a user's monitor?

    That's going to be true in any image editor. The working space gamut is far more important than the display gamut although in a perfect world, you'd be able to see the same gamut as the image. But then most are not viewing the final on a display, they still have to make some kind of print which has it's own unique gamut.

     

    It's far more critical to have an editing space who's gamut is large enough for all our output needs. Adobe RGB (1998) isn't it! Here's why:

     

    Everything you thought you wanted to know about color gamut

    A pretty exhaustive 37 minute video examining the color gamut of RGB working spaces, images and output color spaces. All plotted in 2D and 3D to illustrate color gamut.

     

    High resolution: http://digitaldog.net/files/ColorGamut.mov

    Low Res (YouTube): http://www.youtube.com/watch?v=n0bxSD-Xx-Q

     
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    Apr 10, 2013 10:29 AM   in reply to Victoria Bampton

    I'm asking for clarifying the issue exactly Lightroom does not use the standard or 1:1 previews in the develop module, it uses those previews for other modules except develop module ... right?

     
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    Apr 10, 2013 10:42 AM   in reply to AttilaHan

    And one more question ... ok previews are in Adobe RGB in library module, but I think that the histogram is created according to linear ProPhoto (working space) in the quick develop section. Is it right? Because, I can identify that in some photos histograms are not same with the soft proofing display selected Adobe RGB. They are more like standard develop module histograms.

     
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    Apr 10, 2013 10:45 AM   in reply to AttilaHan

    The previews (which are Adobe RGB jpegs) are used in Library module.  Not sure about all the other modules.  Both Slideshow and Web modules appear to do something different, and I think probably render their own view of the image (rather than using the preview) or they wouldn't take so long doing it. 

     

    In fact, I'm sure web module doesn't use the previews, as it uses sRGB (not Adobe RGB).

     
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    Apr 10, 2013 10:47 AM   in reply to AttilaHan

    I think the histograms (in Develop Module) are created from ProPhoto RGB, but with an sRGB tone response curve applied, not linear.  Not sure how the histogram is created in Library Module. 

     
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  • Andrew Rodney
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    Apr 10, 2013 10:48 AM   in reply to CSS Simon

    The histogram is ProPhoto primaries with a sRGB TRC. Something you never get out of LR which I find ironic for Histogram peepers.

     
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    Apr 10, 2013 11:10 AM   in reply to Andrew Rodney

    Thanks Simon and Andrew,

     

    I've really learnt so many additional things from this topic as a newbie color manager

     

    Total display gamma should be 1, so it is clear that why develop module uses 2.2 ProPhotoRGB ... but indeed we're working on linear ProPhotoRGB.

     
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    Apr 10, 2013 11:24 AM   in reply to image_gsam

    image_gsam wrote:

     

    LR must fit the colors into the gamut that can be displayed on my monitor so that I can see correctly what the effect is of my color editing. How does LR know the gamut of colors that can be displayed on a user's monitor? 

    Very simple: It converts to your monitor profile. That profile is a complete description of the monitor's characteristics, including gamut. Or more precisely: it pinpoints the exact position, in three-dimensional color space, of the three primaries. Out of gamut colors are clipped to the monitor profile gamut.

     

    That's why monitor calibration/profiling is essential, whether the monitor is standard or wide gamut. It's not just about gamma or neutral color balance.

     
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    Apr 10, 2013 11:29 AM   in reply to Andrew Rodney

    Andrew Rodney wrote:

     

    ... for Histogram peepers.

    The histogram seems to be out of fashion, you're not supposed to care about it these days.

     

    But actually it's a fantastic diagnostic tool, and as such underrated. Nobody in their right mind would adjust an image for a "nice" histogram, of course.

     
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    Apr 10, 2013 11:59 AM   in reply to AttilaHan

    AttilaHan wrote:

     

    Total display gamma should be 1, so it is clear that why develop module uses 2.2 ProPhotoRGB ... but indeed we're working on linear ProPhotoRGB.

    Human visual perception follows a power law somewhere near 2 or 2.2 (except at very low and high light levels), so a gamma of 2.2 (or the sRGB Tone Response Curve, which is almost the same) means that the levels in the histogram are approximately perceptually even. In other words, even though the develop module works with a linear tone response curve, it's useful to show a histogram with tone response curve applied of gamma 2.2 or sRGB TRC. 

     
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    Apr 11, 2013 7:53 AM   in reply to twenty_one

    twenty_one wrote:

     

    The histogram seems to be out of fashion, you're not supposed to care about it these days.

     

    But actually it's a fantastic diagnostic tool, and as such underrated. Nobody in their right mind would adjust an image for a "nice" histogram, of course.

    Adobe's decision to apply an sRGB TRC to the Histogram to better match the eye response indicates to me they were trying to make it a more useful tool for image adjustment purposes.

     

    When using PV2012's "image adaptive" controls the first (and most important) adjustment to make is Exposure. I almost always get the best image tonal balance using a slightly overexposed setting of +.5 to +1.0 EV, but didn't know why until I started looking at the LR Histogram.

     

    PV2012 Basic Tone panel controls work best when you see the Highlights (right most zone) maximize in height and just start to compress (i.e. adapt) slightly, and/or the Shadows (left most zone) start to reduce in height and pull away from the left side of the Histogram. Don't be surprised if this setting is +.5 to 1.0 EV for what appears to be a properly in-camera exposed raw image (i.e. ETR).

     

    I'm not saying this will work for every image, but it will for those that have a "normal" tonal balance. It's also a good "starting point" for all images. The Adobe suggested procedure is to "visually" adjust the Exposure control for the best mid-tone balance using the preview image, which is rarely the optimum setting. By watching the Histogram when making PV2012 Tonal adjustments you'll gain a better understanding on how to use these "image adaptive" controls more effectively.

     

    A Gray Scale Test Ramp is a good image to observe what areas the PV2012 Tone controls affect in the Histogram. You can download one at this link:

     

    http://www.northlight-images.co.uk/downloadable_2/test-ramp_2.zip

     

    Open the Gray Scale Test Ramp image in LR and adjust the PV2012 Tone controls one-at-a-time from their '0' default setting. You can also do this using the Tone Curve controls, which work quite differently from the Basic panel Tone controls.

     
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  • Andrew Rodney
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    Apr 11, 2013 9:17 AM   in reply to trshaner

    trshaner wrote:

    Adobe's decision to apply an sRGB TRC to the Histogram to better match the eye response indicates to me they were trying to make it a more useful tool for image adjustment purposes.

    Yeah, kind of... There are two distinct and different ideas here considering ACR came first and LR uses ACR's processing engine. Personally I think the way ACR works with a Histogram makes far more sense. You select the encoding color space you want to use (you only get 4) and the Histogram shows you this. WYSIWYG. LR does something different since originally, there was no soft proofing (which does show you a Histogram based on what you'll get). The idea of showing Melissa RGB when it's not what you're going to get, nor what you're working on at the moment seems to be a case where Histogram peepers need to decide how deep they'll peep.

     
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  • Andrew Rodney
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    Apr 11, 2013 9:20 AM   in reply to twenty_one

    twenty_one wrote:

    The histogram seems to be out of fashion, you're not supposed to care about it these days.

     

    But actually it's a fantastic diagnostic tool, and as such underrated. Nobody in their right mind would adjust an image for a "nice" histogram, of course.

    Like most things, the Histogram has very useful feedback and a lot that isn't. People like to dismiss it outright or make it harder to use than necessary. Thinking of doing a video on it since like many tools we have that date so far back, it's changed a bit over the years. In some cases, a Histogram is useless and tells you nothing about the image data and in some cases, it tells you a lot. It doesn't and never will tell you that the image is pleasing or the desires of it's creator.

     
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    Apr 11, 2013 10:00 AM   in reply to Andrew Rodney

    I agree on that.

     

    In some situations, you sense that an image isn't quite right, but you can't put your finger on it. Surprisingly often, IME, the histogram can tell you exactly what the problem is. But of course you need to properly read and interpret what it says.

     

    It's just that I've read a lot of comments lately (from other people) saying, in effect, "histogram schmistogram" and similar. I believe they're very off-handedly throwing out a useful tool.

     
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    Apr 11, 2013 10:36 AM   in reply to twenty_one

    In the LR PV2012 Exposure setting example I posted the Histogram actually works quite well, despite the difference in color space. This is probably because the Exposure control's primary purpose is to set the Histogram center region (i.e. mid-tones) from the "ballpark" into "center field." It's a pretty "gross" adjustment with lot's of latitude before things get nasty.

     

    What's interesting are the differences between the ACR and LR Histograms, as pointed out by Andrew Rodney. Below is the Gray Scale Test Ramp in ACR 7.4 with sRGB color space setting and LR4.4 with its native sRGB TCR. All controls are at the '0' default settings.

     

    Double-Click on image to see fill-size:

    Histograms.jpg

    The spacing and position of the gray scale patches is about the same, but the LR4.4 Histogram has a strange "spread" at the base of each gray scale patch (i.e. spike). This should have little affect on using the Histogram for "visually" making adjustments, but why is it different? In addition would using Soft Proof provide a more accurate Histogram profile for making Tonal adjustments in LR, and what profile should be used, etc?

     

    Andrew, I would love to see a video tutorial on the PS, ACR and LR histograms, with details on differences, and how to use them better. You've got my vote!

     
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