Thread: Taran van H. asks "how exactly does a reference [video] monitor work?" I answer...

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  1. #1 Taran van H. asks "how exactly does a reference [video] monitor work?" I answer... 
    On Sept 14th, Taran van Hemert published an hour-long video titled "HOW THE F*** DOES SCREEN CALIBRATION WORK? - Tutorial"



    In that video he asked "QUESTION 5: How exactly do reference monitors work?" and noted our video response, which was shot the next morning on a RED Hydrogen One cameraphone:



    That led to more questions, which led to this video:



    Which led to this response from Taran:

    So you're not talking about the screen colors being much more saturated, you're talking about the scopes CLAIMING that the colors are much more saturated.... correct?

    Anyway, I don't expect you to grab a RED camera and a tripod like I did. It was only that one point that I couldn't quite follow
    Well...Challenge accepted. An instead of using a RED camera to provide some more definitive details, I used three: a Monstro and two Helium S35 cameras.

    This video is the narrative that explains what is being demonstrated, what is being displayed, and what can be understood from a rather complex test setup:



    Once the narrative makes clear what's what, you can look at the raw video data, displayed 4-up in UHD here:



    For more info about the Flanders Scientific DM240 Reference Video Monitor, check out http://flandersscientific.com/DM240/

    Happy calibrating!
    Michael Tiemann, Chapel Hill NC

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  2. #2  
    Senior Member Patrick Tresch's Avatar
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    Isn't it that the scope is monitoring the input signal and not the mode in wich the monitor is set?
    You had the same "problem" when you monitored the BW picture with the 0-255 values (Full/Data) from Davinci and you changed the monitor 709 to DATA levels. The scope stayed at Data level (with 0-16 and 235-255 values in red) even if the monitor compensated for the right ouput level.
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  3. #3  
    Quote Originally Posted by Patrick Tresch View Post
    Isn't it that the scope is monitoring the input signal and not the mode in wich the monitor is set?
    You had the same "problem" when you monitored the BW picture with the 0-255 values (Full/Data) from Davinci and you changed the monitor 709 to DATA levels. The scope stayed at Data level (with 0-16 and 235-255 values in red) even if the monitor compensated for the right ouput level.
    Sorry for the confusion. The "Data" label refers to the "Video Data" scope in the DM240, not the signal level (which is sometimes called Data). All signals were set to be full scale, as was the monitor. After I shot the video, I changed the breakpoint in the Realtime scopes so that IRE -8 is Blue, IRE -7 to -1 is Red, 0 to 100 is Green, 101-107 is Red, and 108 is Blue. I could change up the colors in other ways, but that's how I have those scopes set for right now (though in retrospect I can see why using Red colors might cause some to say "whoa! That's an error!").
    Michael Tiemann, Chapel Hill NC

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  4. #4  
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    You are delivering video to some standard display referenced color space, REC709 still being most typical. That is what the monitor is supposed to show and the scopes act as a reference for. Both need to be calibrated for the chosen delivery display color space to be accurate for grading. The camera color space is irrelevant.

    I generally work in full 10 bit data range in Resolve, with reference lines for REC709 set at 64 for black and 940 for white on the waveform scope.
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  5. #5  
    Quote Originally Posted by David Rasberry View Post
    You are delivering video to some standard display referenced color space, REC709 still being most typical.
    Yes, and...

    That is what the monitor is supposed to show and the scopes act as a reference for. Both need to be calibrated for the chosen delivery display color space to be accurate for grading.
    Yes and Yes and...

    The camera color space is irrelevant.
    No in this case. Of course if Taran doesn't have a monitor that can display the full gamut of REC2020, then there's no way for him to directly experience how the DM240's display of the 2020 color gamut compares to its display of the 709 color gamut, but the data captured by the cameras of these two different results--if the camera color space is large enough--allows one to see some kind of difference and then mathematically measure the video data captured by the camera to really see what's what. Which is what I think he was asking for.

    I generally work in full 10 bit data range in Resolve, with reference lines for REC709 set at 64 for black and 940 for white on the waveform scope.
    IOW, you allow Resolve the full data range but you work your grades to fit within the Video limits of 10-bit, which can then be properly interpreted by a video monitor whose black and white points are expecting video-level. not data-level signals. Makes sense to me!
    Michael Tiemann, Chapel Hill NC

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  6. #6  
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    Thanks for the explanation about viewing camera gamuts. Not something I was aware of as an option. Do any monitors actually display full REC2020 gamut?
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  7. #7  
    I don't know any full Rec 2020 monitors as of yet.
    Michael Tiemann, Chapel Hill NC

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