Small Gamut coverage after Profiling with a RGB Laser projector

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  • #39052

    SirMaster
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    Yeah, the circumstances for the color performance of the Formovie is somewhat unfortunate in terms of accuracy and calibration.

    I am not sure what you can ultimately do in the end. Either try making a 3DLUT with all the different rendering intents and see which you like the most. (You don’t have to re-measure every time, you can just load the profile you made and generate another 3LDUT with the new rendering intent)

    Or calibrate manually as best you can with the projectors color controls instead.

    I agree that lowering the white level is not any solution.  But at least know that what you are seeing is normal and what I saw as well. So you unit is not defective and you are not doing anything wrong.

    #39053

    Dennis23
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    To be honest, the picture of the projector is great beside these issues.

    2400:1 native contrast @ D65 is upper class for a consumer DLP and not many other DLP projectors can throw such a contrasty image. I have also an old Marantz VP-15S1, which has a 0.95 inch Darkchip 3 and has cost over 10 grand new when it came out about 10 years ago, and even this projector has only about 2000:1 contrast but only @ 500 lumens calibrated in high lamp mode. The Formovie can deliver more contrast and is 3x times brighter. The Marantz has more accurate colors in BT709 though and does not necessary need a 3D LUT.

    The Formovie needs some serious calibration work to get it near target. Gamma and greyscale are almost perfect after just touching the gain control. The biggest issue is cyan and magenta and the color luminances of all colors at higher saturation levels.

    I tried all rendering intents like you said and the only one which looks appealing to me is the “preserve saturation” one, but only after polishing it with the projector’s CMS further.

    I will also take a look at ColourSpace from Light Illusion. I know that the software is not cheap, but I begin to get somewhat enthusiastic regarding 3D LUT’s and color accuracy overall. And I pretty often change my projectors so it might be worth to invest one time for the future to get the best results as possible. I also have to mention that DisplayCal is a great software and that is even for free. For an average enthusiast and for projectors which are not complicated like the Formovie, there is no better solution IMHO.

    • This reply was modified 1 year, 1 month ago by Dennis23.
    • This reply was modified 1 year, 1 month ago by Dennis23.
    • This reply was modified 1 year, 1 month ago by Dennis23.
    #39066

    Vincent
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    I did now two tests and reduced the brightness one time to 50 and another time to 30 cd/m² instead of “as measured”. The untouched brightness before was about 85 cd/m².

    The BT709 gamut coverage has risen from 82 to 90% in both tests. That means even reducing it below 50 cd/m² does not make any difference.

    After measuring the result with the active 3D LUT and with the rendering intent “absolute colorimetric with white point scaling” the only thing that has changed is that the 100% red saturation is now matched with the target correctly. But cyan still keeps undersaturated, even @ 30 cd/m².

    But even if the result is a bit better because of the correct red saturations now, it is not a solution, due to the low contrast and brightness loss. I hoped that there would be anything I can do, even if that means low color  luminance @ 75 and 100% saturation.

    Just hitting the saturation and hue targets of all colors would be enough for me honestly, because it’s almost impossible for the eye to know if a 75 or 100% saturated color is a bit darker than it should be, without having a correctly calibrated display in direct comparison.

    But the undersaturated cyan is easily visible for me without direct comparison.

    As I said above (or if I did not i said teh same to other person), first of all you need to test if profile used as destination matches display/projector.

    It that fails, it’s not a matter of rendering intents, but to a very irregular display response.

    Every time you get some weird behavior first of all test is data used as input is valid (dislay profile)

    Problem ist, that DisplayCal has no other rendering intent options beside “preserve saturation” which could provide a better result and here the oversaturation is a bit too strong for my taste. At the moment the only solution seems touching the CMS of the projector after applying the 3D LUT to do further corrections.

    DisplayCAL is just a GUI, for full manual options in LUT3D creation:

    http://www.argyllcms.com/doc/collink.html

     -a file.cal        Apply calibration curves to link output and append linear
     -H file.cal        Append calibration curves to 3dlut
     -O file.cal        Use just calibration curves as link and append linear
     -s                 Simple Mode (default)
     -g [src.gam]       Gamut Mapping Mode [optional source image gamut]
     -G [src.gam]       Gamut Mapping Mode using inverse outprofile A2B [optional source gamut]
    
    
    
         Simple Mode Options:
     -i in_intent      p = perceptual, r = relative colorimetric,
                       s = saturation, a = absolute colorimetric
     -o out_intent     p = perceptual, r = relative colorimetric,
                       s = saturation, a = absolute colorimetric
    
    
    
         Mapping Mode Options:
     -i intent      set linking intent from the following choice:
                  a - Absolute Colorimetric (in Jab) [ICC Absolute Colorimetric]
                 aw - Absolute Colorimetric (in Jab) with scaling to fit white point
                 aa - Absolute Appearance
                  r - White Point Matched Appearance [ICC Relative Colorimetric]
                 la - Luminance matched Appearance
                  p - Perceptual (Preferred) [ICC Perceptual]
                 pa - Perceptual Appearance
                 lp - Luminance Preserving Perceptual
                 ms - Saturation
                  s - Enhanced Saturation [ICC Saturation]
                 al - Absolute Colorimetric (Lab)
                 rl - White Point Matched Colorimetric (Lab)
     -w [J,a,b]     Use forced whitepoint hack [optional color to map the white to]
     -b             Use RGB->RGB forced black point hack
     -c viewcond    set source viewing conditions for CIECAM02,
                      either an enumerated choice, or a parameter
     -d viewcond    set destination viewing conditions for CIECAM02,
                      either an enumerated choice, or a parameter:value change
                  pc - Critical print evaluation environment (ISO-3664 P1)
                  pp - Practical Reflection Print (ISO-3664 P2)
                  pe - Print evaluation environment (CIE 116-1995)
                  pm - Print evaluation with partial Mid-tone adapation
                  mt - Monitor in typical work environment
                  mb - Monitor in bright work environment
                  md - Monitor in darkened work environment
                  jm - Projector in dim environment
                  jd - Projector in dark environment
                 pcd - Photo CD - original scene outdoors
                  ob - Original scene - Bright Outdoors
                  cx - Cut Sheet Transparencies on a viewing box
              s:surround n = auto, a = average, m = dim, d = dark,
                         c = transparency (default average)
              w:X:Y:Z       Adapted white point as XYZ (default media white)
              w:x:y         Adapted white point as x, y
              a:adaptation  Adaptatation luminance in cd.m^2 (default 50.0)
              b:background  Background % of image luminance (default 20)
              l:imagewhite  Image white in cd.m^2 if surround = auto (default 250)
              f:flare       Flare light % of image luminance (default 0)
              g:glare       Glare light % of ambient (default 5)
              g:X:Y:Z       Glare color as XYZ (default media white)
              g:x:y         Glare color as x, y
              h:hkscale     Helmholtz-Kohlrausch effect scale factor (default 1.0)
              m:mtaf        Mid-tone partial adaptation factor (default 0.0)
              m:X:Y:Z       Mid-tone Adaptation white as XYZ (default D50)
              m:x:y         Mid-tone Adaptation white as x, y

    But maybe there is anything hidden, which I haven’t find out yet. That is the big question

    The next thing I can try now is to rise all color luminances to its maximum in the CMS of the projector before profiling, maybe that will make a difference and DisplayCal will give better results.

    Try to validate if display ICC profile matches display (3D mesh with monitor behavior “raw RGB” <-> CIE XYZ if you had an XYZLUT ICC profile)  as the first step before doing other things.

    #39069

    Dennis23
    Participant
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    Thank you for your reply and suggestions.

    I will try to do what you wrote, even if seems a bit complicated for me as a beginner at creating 3D LUTs. Many terms are not yet clear to me and I should read more to get a basic understanding. With your help, there may be hope to get it right.

    • This reply was modified 1 year, 1 month ago by Dennis23.
    #39076

    Vincent
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    Verification of profile is a simple task: unload LUT3D from whatever HW or SW you loaded it, make sure custom ICC profile for display is assigned as default dsplay profile in OS and then run a measurement report.
    Choose a big patch like those ISO 300+ patches, you want to measure how bad profile predicts display behavior in a 3d mesh near the troublesome zones from your past posts.

    Once you have done this you may try to find best rendering intent settings. Start with equivalent commandline for collink created by DisplaYCAL (should be on the logs) and then apply whateeer additional tweak you find will improve visual outcome.

    • This reply was modified 1 year, 1 month ago by Vincent.
    • This reply was modified 1 year, 1 month ago by Vincent.
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