A Guide to Wide-Gamut Displays (v1.2)

Discussion in 'Video Cards & Monitors' started by Maldark, Oct 20, 2008.

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  1. Maldark

    Maldark Member

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    A Guide to Wide-Gamut Displays (v1.3)

    This thread spawns as the direction my frustration took with my new wide-gamut display (Dell 2408WFP). I was disappointed with the oversaturated colours on my desktop, in my internet browser, in movies and games and have rigorously scoured the internet looking for solutions. Now you lucky folks get to bear the fruits of my labour. I present a guide to wide-gamut displays.


    What’s new?

    v1.3-added a much easier method of retrieving colour primaries to the MPC section, credit goes to kkant for this, cheers!

    v1.2–proof read, changed a lot of sentences to make more sense.
    -added some extra content on colour managed web-browsers
    -added requirement for MPC fix
    -added my method of finding colour primaries
    -added information on gamma correction for MPC
    -added “Drawbacks of colour space matching.” Section
    -added “Colour managing on multiple screens.” Section

    v1.0-My first draft, hope everyone enjoys :D

    Contents
    1. What is a wide-gamut monitor, and why should I care?
    2. A brief introduction to colour space.
    3. Colour aware browsing, oh what a difference.
    4. Experimental colour correction in Media Player Classic[Requires DirectX 9 capable graphics card]
    5. Problems which have no known solution... yet.
    6. Drawbacks of colour space matching.
    7. Colour managing on multiple screens.
    8. A work in progress.


    1. What is a wide-gamut monitor, and why should I care?

    In brief, a wide-gamut monitor is a monitor which is capable of displaying a wider range of colours than a standard gamut (sRGB) monitor (more on this later). At first this sounds to be advantageous, who wouldn't want more colours? The ability to reproduce larger parts of the optical spectrum is surely a good thing right? More colours would mean more life-like photos, more realistic movies, and better more vivid games right? The answer is yes, but... what happens if the software and hardware are unaware of these extra colours? Well, this would mean that the colours sent to your monitor would be displayed inaccurately. Since this new outburst of wide-gamut monitors is only recent software is still used to sending out standard gamut colours so the displayed colours are “stretched”. This leads to games, movies and just about everything looking overly colourful, and bright. But who cares right? what's a little colour between friends, well some people (myself included) much prefer that their computer be able to accurately reproduce the original colours of source materials (in games or movies etc) I prefer that people's faces don't look red in movies or on facebook, and I prefer that the colours I experience are exactly what the author had intended. Now that you're aware of some of the drawbacks, lets look at methods for combating this. I'll start with an introduction into colour space.


    2. A brief introduction to colour space.

    A colour space is a range of colours which is defined within the visible spectrum of colours. The below image represents the full range of visible colour and the black triangles represent different industry defined colour spaces.
    [​IMG]

    The main colour space we're concerned with here is the sRGB colour space. This is the standard range of colours used in games, movies and the web. Traditionally monitors had colour spaces similar to that of sRGB so that colours were represented accurately. However with the introduction of wide-gamut displays this has changed. Lets see what a difference it makes.

    When your computer communicates with your monitor it sends colour signals as a string of 8-bit code. That is three numbers representing the coordinates for red green and blue in the format (Red,Green,Blue) with each colour being assigned a value between 0-255. Now when your computer sends through a signal for a colour it expects that the colour displayed on your monitor will correspond to the correct coordinate in the sRGB colour space. If your monitor has an extended gamut the colours are stretched. That is if your monitor received the signal for pure green (0,255,0) then it's expected that it would display the greenest vale in the sRGB colour space. An extended gamut monitor would produce its greenest value which may lie well outside of the sRGB gamut. This can be better represented visually by the image below.
    [​IMG]

    The orange triangle is the sRGB space, the black triangle is my monitors colour space. As you can see the difference between the expected green value and the displayed green value is quite large. This leads to inaccurate, oversaturated colours on your display.

    All is not lost though, accurate colours can be obtained your computer just needs to scale the signal before it's sent to your monitor so that the correct sRGB values can be displayed. This is another sore spot at the moment, very few applications allow you to do this, so most things (movies, games, desktop) will appear oversaturated and "cartoony". In the future more programs may be created to take full advantage of these wide-gamut displays, but until they maintain a large market share, there’s no point in using colours that the majority of people with sRGB monitors won’t be able to see. If the reverse is true in the above case and the colour space of the program is outside of the colour space of the monitor then the colours will be crushed into the colour space of the monitor leading once again to inaccurate colours. The following segment will walk you through a solution to this problem for an internet browser (FireFox3) and an experimental solution for a media player (Media Player Classic).


    3. Colour aware browsing, oh what a difference.

    This solution is very simple, you will need:
    FireFox 3 (http://www.mozilla.com/en-US/)
    The FF3 Colour Management add-on (https://addons.mozilla.org/en-US/firefox/addon/6891)
    You will also need the colour profile for your monitor (either .icc or .icm files are accepted).

    The colour profiles are most preferentially obtained using a colour calibrator to ensure the most accurate colours for your display, however some manufactures (ie. Dell) do supply the colour profiles on your driver disc. If neither of these are obtainable you could resort to downloading one off someone with a calibrated monitor of the same model. Do note however that colour profiles are different for every display and even within models the colours may change a little bit.

    So simply install FF, install the add-on. Open the add-on in "Tools->Add-ons" and load your colour profile into it. If you cannot find your colour profile the default directory is "c:/Windows/System32/Spool/Drivers/Color".

    Colour management in FF doesn’t just mean accurate colours for sRGB content on the internet. It also means that material that has been embedded with colour profile information (Images that use colours outside of the standard gamut can be tagged with a copy of the gamut used in their creation) can be correctly displayed on monitors with a large enough range of colours (Most commonly the Adobe-RGB space, this space requires a wide-gamut monitor to display correctly).

    Here is an excellent website http://www.gballard.net/photoshop/srgb_wide_gamut.html it will show you the difference between a colour managed application and a non-colour managed application and allow you to see the dramatic difference in colour accuracy after the add-on has been enabled. It also shows IEs ineptitude at colour management.


    4. Experimental colour correction in Media Player Classic [Requires DirectX 9 capable graphics card]

    This is a rather complex solution to what one would think to be a rather simple problem, but apparently not. No media player (to my knowledge) comes with the ability to colour manage, this may happen in the future, but for now this is the best (and only) solution I've found. I take no credit for this solution, the original post can be found over on http://www.avsforum.com/avs-vb/showthread.php?t=912720 . I've edited out all the techno-babble and provide only a walkthrough to the solution, if you want more in-depth details see the thread.

    Step 1a-Update your DirectX runtime for the latest version. (http://www.microsoft.com/downloads/...38-db71-4c1b-bc6a-9b6652cd92a3&displaylang=en)
    Step 1b-Download Media Player Classic. (http://www.free-codecs.com/download/Media_Player_Classic.htm) It may need FFD Show, I'll await confirmation from anyone who tries it.
    Step 2-Run “mplayerc.exe”.
    Step 3-Select “View->Shader Editor”.
    Step 4-In the top field write the name you want for the shader (I used “Colour Correction”) and press “Enter”.
    Step 5-In the field on the right of the name make sure “ps_2_0” is selected.
    Step 6-Find your monitors primary colour coordinates. Open the monitor's profile using ICC profile Inspector(http://www.color.org/ICCProfileInspector.zip), and double click the items labeled rXYZ, gXYZ, and bXYZ. This will give you a new screen with the exact XYZ coordinates of the selected primary color. If you're having trouble finding your profile it's most likely located in C:\Windows\System32\spool\drivers\color.
    Step 7-Enter your monitors primary coordinates into this document (http://www.megaupload.com/?d=1726XM3X If someone could suggest a better file host that'd be appreciated).
    [​IMG]
    Step 8-Copy the code into MPC and exit the shader editor by clicking the cross. Your code will look something like this.
    Code:
    sampler s0 : register(s0);
    float4 p0 : register(c0);
    
    static float4x4 r2r =
    {
    0.668312280328261,0.301859946936631,0.0298277727351087,0,
    0.0387623696123455,1.00634289651699,-0.0451052661293355,0,
    0.00901850955009226,0.0442793347980067,0.946702155651903,0,
    0, 0, 0, 0
    };
    
    float4 main(float2 tex : TEXCOORD0) : COLOR
    {
        float4 c0 = tex2D(s0, tex);
        c0 = pow(c0, 2.2);
        c0 = mul(r2r, c0);
        c0 = saturate(c0);
        c0 = pow(c0, 1/2.2);
    
        return c0;
    }
    
    Step 9-Go to "View->Options->Playback->Output" and select:
    -DirectShow Video: VMR9(Renderless)
    -Surface: 3D Surfaces
    Step 10-Play your video.
    Step 11-Go to Play->Shaders and select the shader you want.

    Now, if you've done this correctly the colours displayed should be corrected to the sRGB colour space. I found this solution very effective, the code included is the code I'm personally using so any other Dell 2408WFP users could just try that directly if they don't know their primary colour coordinates. If you’ve been bold and calibrated your monitor for a non-standard Gamma (i.e. not 2.2) then the values “c0 = pow(c0, 2.2);” and “c0 = pow(c0, 1/2.2);” should be changed accordingly.


    5. Problems which have no known solution... yet.

    Ok, so far I’ve shown solutions for internet browsing and movie playback. There are still quite a few problems which have no current solution. Windows as a whole is still not colour aware, so icons and colours may appear oversaturated. Games are also not colour aware, every game to date has been designed in the sRGB colour space (because up until recently that's what most monitors have been reproducing) so colours in games will be inaccurate until a solution is produced. The obvious solution is a colour aware operating system which just automatically tags non-colour managed content as sRGB and rescales the output signal accordingly, perhaps we will see something like this in the future, but unfortunately there's currently no such thing available.


    6. Drawbacks of colour space matching.

    The methods used above have some serious problems associated with them. The main being an increase in colour separation. With the current signal system (8-bits per channel for a full range of 24-bit colour) adjacent colours can be represented once again as a string of three numbers. The closest any two possible colours can be is a difference of 1 on one channel (eg. (253,35,5) and (253,35,6)) so as we expand the area over which this signal extends the difference between adjacent colours increases (i.e. the difference between two adjacent colours in the sRGB space will be smaller than two adjacent colours on a wide-gamut display). This means that banding is more likely to occur the larger we stretch the gamut and it also means that reproducing sRGB content with a larger gamut will produce less correct colour (It’s more accurate in that the colours are closer to their true colours than when stretched to a wide-gamut, but it’s less accurate in that there’s a greater spacing between adjacent colours).

    There is a solution to this, however the timeline for its introduction is unknown. If the computer were to use a higher amount of bits/colour-channel then there would be a larger amount of colours and hence the banding could be avoided. 10-bit/channel and even 16-bit/channel displays are in development so this could become a reality soon, but it doesn’t help current wide-gamut screen owners.


    7. Colour managing on multiple screens.

    If you’re like me then one screen just isn’t enough, you need at least two. Now, what happens in all those lovely colour managed applications when both your screens don’t share the same colour gamut? Well, they don’t like it that’s for sure. Applications with require you to load your monitors colour profile (FF3, the MPC fix, photoshop etc.) will only look correct on the monitor whose profile you loaded. Also most colour aware applications won’t let you change your colour profile without restarting the application so that’s a pain. In my journeys I have discovered one such mythical program. Windows Photo Gallery (of all things :S) on Windows Vista correctly identifies the colour profiles loaded in windows colour management and accurately displays the colours, even when Windows Photo Viewer is stretched across both monitors. If more programs would utilise Vistas inbuilt colour management system in the same way this guide would no longer exist (I dream of such a day).


    8. A work in progress.

    This guide was designed for people who are like I was about a week ago, frustrated with the colour displayed on their shiny new wide-gamut display. All the information above is simply what I’ve compiled in my internet rummaging and is probably inaccurate in parts. For this reason I request that anyone with criticisms, or questions post them so I can improve this guide (even spelling errors).
     
    Last edited by a moderator: Mar 5, 2010
  2. MrSmoke

    MrSmoke Member

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    nice, i now know what Gamut means :p
    definitely interesting
     
  3. g0bbles

    g0bbles Member

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    I will never view a colour as being boring again.

    Good article..!
     
  4. Kaine[zof]

    Kaine[zof] Member

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    Great article, looking forward to updates. We really need a way to find the appropriate info for any monitor. Your method with the Gamut map is a great starting point, even if it confused me a little. I use a rather obscure Proview 22" monitor (FP-2226AFW) and finding any kind of color profile for it is damn near impossible. The Chei Mei 221D is the closest common monitor I can think of as it uses the same panel. Colour reproduction particularly in movies and TV on this monitor has always pissed me off. Almost enough to rig up one of my old P76 17" CRTs (fantastic colour :thumbup:)
     
  5. nexx

    nexx Member

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    I'm getting a wide gamut monitor later on in the week so these guides will be very helpful. Thank you :)
     
  6. Whisper

    Whisper Member

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    Great Post Maldark
     
  7. monkeyMadness

    monkeyMadness Member

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    definitely a great article! thanks maldark!
     
  8. stalin

    stalin (Taking a Break)

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    Just a big :thumbup: glad you took the time to post such quality information, shame there isn't more people like you out there.
     
  9. qbson

    qbson Member

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    color aware software

    Hi

    My first post here so I would like to say hello to everyone.
    Maldark - thank you so much for your initiative! After over 1 week of extensive searching on the Internet it is the only place where wide gamut issue is so comprehensively covered.

    If I may suggest anything then I would kindly ask to add one more point to your topic: Colour Aware Software.
    You've already started with FF and Media Player Classic (you mentioned also Photoshop).
    I may add very nice free image viewer with full colour management: Fast Picture Viewer. It converts sRGB to aRGB without any difficulties. All you need to do is to load your ICC to it (Menu -> Display... -> Enable Color Management... -> Override target profile). Tested on Windows XP and HP LP2475w.

    Thanks again
    qbson
     
    Last edited: Oct 23, 2008
  10. Cheatz

    Cheatz Member

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    Great personal article with an easy to understand format removing complex techno babble speak. Going by your comments of future o/s i'm guessing windows 7 will not feature wide gamut support?
     
  11. DiGiTaL MoNkEY

    DiGiTaL MoNkEY Inverted Monkey

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    thanks for the article, interesting info.
     
  12. Carby

    Carby Member

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    So color management tab is useless?

    A truly excellent article. I won't be so quick to ignore those CD's that come with monitors from now on.

    I would have thought that the place to truly fix this would be in the video card. Investigating video options I found what seems to be a windows thing.

    Windows XP SP2 with nvidia driver version 175.19
    Right click desktop -> Settings Tab -> Advanced button -> Color Management tab. Looks like a spot to add icm or icc files.

    I found and applied one for my Samsung 204B but didn't notice anything different. But then I am pretty sure it is not "wide-gamut".
     
  13. Maldark

    Maldark Member

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    This is how you colour correct monitors, but it is not colour management. This dosn't change the fact that the system is reporting incorrect (oversaturated) colours to the monitor it only corrects the shape of each colour's gamma curve. If the OS used the file correctly to not only correct for gamma, but also for gamut then this with resolve all of the colour issues.

    I hope that helps.
     
  14. jayjones1

    jayjones1 New Member

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    cheers thanks for the info [​IMG]
     
  15. kkant

    kkant New Member

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    Here's a way to easily find the exact RGB coordinates of a monitor ICM profile. Get this software:

    http://www.color.org/ICCProfileInspector.zip

    This is an ICC profile reader. Open the monitor's ICC profile, and double click the items labeled rXYZ, gXYZ, and bXYZ. This will give you a new screen with the exact XYZ coordinates of the selected primary color.

    Please add this to the original post. :)
     
  16. Afurotsu

    Afurotsu Member

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    Great find kkant :). Makes step 4 much simpler.
     
  17. Maldark

    Maldark Member

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    Edited, with apropriate crediting to you kkant, thanks!
     
  18. mthien

    mthien Member

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    Last edited: Jun 3, 2009
  19. Mickatroid

    Mickatroid Member

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    I followed the instructions and it is beautiful on my HP LP2475W. I still don't fully understand exactly what is being adjusted where, I need to read this all a few more times :)

    Thanks.
     
  20. OldnBold

    OldnBold Member

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    A good article which should be tempered with the advice given here that full color (sic .. US spelling .. sigh .. of course they mean colour) profiling will not be instituted with Firefox until 3.1:

    http://bholley.wordpress.com/2008/09/12/so-many-colors/

    What may help people is a collection of colour profiling ICS files which have been proven using colour correction equipment such as those used from applying Spyder (Datacolor) hardware to the monitors.

    I would be happy to post a link to my ICS for a Samsung 245T, perhaps others who use the Spyder could also do so. This would give forum members access to solid ICS profiles even if they do not have the Spyder hardware.

    Thanks for your efforts.
     

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