A "clean" monitor characterization?

Home Forums General Discussion A "clean" monitor characterization?

This topic contains 15 replies, has 3 voices, and was last updated by  Alex Sikorsky 1 week, 2 days ago.

Viewing 15 posts - 1 through 15 (of 16 total)
  • Author
    Posts
  • #16235

    Alex Sikorsky
    Participant
    • Offline

    – How to characterize the monitor without resetting the calibration curve in the video adapter LUT?

    – How to make spot measurements of the desired color without resetting the contents of the video adapter’s LUT? (Is it possible to use the white point correction menu for this?)

    #16255

    Vincent
    Participant
    • Offline

    – How to characterize the monitor without resetting the calibration curve in the video adapter LUT?

    Set all calibration targets to native, button for calibrate & profile should switch to profile.
    When it ask you for LUT contents say preverve current content instead of clear it and use linear LUT.

    – How to make spot measurements of the desired color without resetting the contents of the video adapter’s LUT? (Is it possible to use the white point correction menu for this?)

    AFAIK “free measurement” is not supported by DisplayCAL. Buy you can use  ArgyllCMS’ “spotread” in command line. It’s easy to use, for example for a CCSS correctable colorimeter should be something like:
    spotread -v -X CCSS_FILE_PATH.ccss
    and there is another option for ambient light. After setup colorimeter communication it ask you to hit a key for measuring.

    #16269

    Alex Sikorsky
    Participant
    • Offline

    – How to characterize the monitor without resetting the calibration curve in the video adapter LUT?

    Set all calibration targets to native, button for calibrate & profile should switch to profile.
    When it ask you for LUT contents say preverve current content instead of clear it and use linear LUT.

    Yes, I have already tried it. I have a software that in real time shows the content of the video adapter LUT. (Shift + Сtrl + ALT + O) –   Enable cyclic reading of data from the LUT video card   (see attachment). Soft>> . And in the version that you wrote during calibration, the contents are automatically reset. Maybe I did not take into account (?!), I will try again.

    – How to make spot measurements of the desired color without resetting the contents of the video adapter’s LUT? (Is it possible to use the white point correction menu for this?)

    AFAIK “free measurement” is not supported by DisplayCAL. Buy you can use  ArgyllCMS’ “spotread” in command line. It’s easy to use, for example for a CCSS correctable colorimeter should be something like:
    spotread -v -X CCSS_FILE_PATH.ccss
    and there is another option for ambient light. After setup colorimeter communication it ask you to hit a key for measuring.

    Thanks, but I want to get away from the command line.

    Attachments:
    You must be logged in to view attached files.
    #16274

    Alex Sikorsky
    Participant
    • Offline

    – How to characterize the monitor without resetting the calibration curve in the video adapter LUT?

    Set all calibration targets to native, button for calibrate & profile should switch to profile.
    When it ask you for LUT contents say preverve current content instead of clear it and use linear LUT.

    Maybe I did not take into account the specific sequential action? – But I will try again when there is free time. Below see the settings, that I set.

    Attachments:
    You must be logged in to view attached files.
    #16278

    Vincent
    Participant
    • Offline

    You set Tone curve to L*, so if you click “calibrate & profile” it is going to reset graphics card LUT because it needs to calibrate to L* and native white.

    Set it to “as measured” as the others, the button on the botton will change to “Profile only”. When you press it (at least older DisplayCAL versions) it shows a popup asking you:
    -do you want to reset video card LUT or keep current contents?
    -do you want to attach a calibration (VCGT) to profile?
    I do not remember the exact sentences, but each one is answered by user with a YES/NO checkbox.
    It seems that you want to store current caibration in profile and keep that calibration while profiling, so use checkboxes to answer that.

    #16292

    Alex Sikorsky
    Participant
    • Offline

    You set Tone curve to L*, so if you click “calibrate & profile” it is going to reset graphics card LUT because it needs to calibrate to L* and native white.

    Set it to “as measured” as the others, the button on the botton will change to “Profile only”. When you press it (at least older DisplayCAL versions) it shows a popup asking you:
    -do you want to reset video card LUT or keep current contents?
    -do you want to attach a calibration (VCGT) to profile?
    I do not remember the exact sentences, but each one is answered by user with a YES/NO checkbox.
    It seems that you want to store current caibration in profile and keep that calibration while profiling, so use checkboxes to answer that.

    I want, having already calibrated the monitor with the generated curves for the ‘TRC’ tags (single curves, according to the target gamma function) and ‘VCGT’ (compensation contained in the video adapter LUT), simply characterize and get the new CLUT tables of the ‘BtoA’ tags . I have just checked, but for almost all modes the value of the video adapter’s LUT is demolished for the duration of the measurements, and this area is technically used for measurements! Those. I did not see a pure characterization … see the screens below. In the intermediate form appearing it is proposed to choose the following:

    The current calibration curves wil be used. Do you want to continue?
    1) Use linear calibration instead. [ _ ] – No?
    2) Embed calibration curves in profile. [ + ] – Yes?
    [ Ok ]

    I used the Calibrilla program to monitor the content of the LUT of the video adapter during characterization in DisplayCAL

    Attachments:
    You must be logged in to view attached files.
    #16307

    Vincent
    Participant
    • Offline

    The current calibration curves wil be used. Do you want to continue?
    1) Use linear calibration instead. [ _ ] – No?
    2) Embed calibration curves in profile. [ + ] – Yes?
    [ Ok ]

    I used the Calibrilla program to monitor the content of the LUT of the video adapter during characterization in DisplayCAL

    Yes, that configuration. I’ve not tested it in latest DisplayCAL version but it worked that way in older versions:
    -do not clean lut (NO, as you did)
    -store VCGT in resulting profile (YES, as you did)

    Colorimeter initialization may lead to VCGT reset & load (I do not remember) but while profiling patches are being measured VCGT should have your old calibration.

    #16309

    Alex Sikorsky
    Participant
    • Offline

    Colorimeter initialization may lead to VCGT reset & load (I do not remember) but while profiling patches are being measured VCGT should have your old calibration.

    Yes, and this just was not!

    #16310

    Vincent
    Participant
    • Offline

    Colorimeter initialization may lead to VCGT reset & load (I do not remember) but while profiling patches are being measured VCGT should have your old calibration.

    Yes, and this just was not!

    I am not sure if I understood what you wrote.

    Task initialization can do whatever needs to do (like reset & reload). It does not matter at all as long as while *profilling patches* are sent to display your desired VCGT contents are loaded into graphics card LUT.

    #16344

    Alex Sikorsky
    Participant
    • Offline

    Colorimeter initialization may lead to VCGT reset & load (I do not remember) but while profiling patches are being measured VCGT should have your old calibration.

    Yes, and this just was not!

    I am not sure if I understood what you wrote.

    Task initialization can do whatever needs to do (like reset & reload). It does not matter at all as long as while *profilling patches* are sent to display your desired VCGT contents are loaded into graphics card LUT.

    After calibration settings, the program should simply make measurements and this is the essence of characterization. At the moment, it resets the calibration settings, takes measurements, using the video adapter as a buffer for adjustments of the LUT, while conducting parallel measurements (this is easy to track by running the parallel display of what is happening in the LUT using Calibrilla). After measurements, the program re-fills the video adapter’s LUT data, but this data has already been changed. Initialization of the device has nothing to do with it. What happens to the data that was reset during the characterization is not clear. – Whether they are used mathematically from the buffer during characterization or not is not clear, but it cannot be verified.

    Attachments:
    You must be logged in to view attached files.
    #16347

    Alex Sikorsky
    Participant
    • Offline

    The picture above shows the state of calibration before characterization, and on the current one after it. It is seen that the entire calibration setting has changed radically.

    The question of the whole post is how to measure without changing the calibration results?

    Attachments:
    You must be logged in to view attached files.
    #16352

    Vincent
    Participant
    • Offline

    If calibration (VCGT contents) has changed form your reference calibration it means:

    -you did not “Profile only” but “Calibrate & profile”. That is an user error

    or

    -you configured it properly for “Profile only” but calibration loaded into VCGT is not the one you wanted. That usually is an user error.

    or

    -some rogue application is messing with VCGT (use “autoruns” or other tools to find out if there is another application in startup)

    or

    -newer DisplayCAL versions changed this functionality or have some kind of bug, since older version could do profile only keeping olde calibrations without issue.

    Best way to find out what is happening is to attach your “old” calibration folder (with .icm and .cal files), the log file/window from your profile “profile only” attempt and the resulting icm profile (with .icm and .cal files).
    DisplayCAL profiles store its related files somewhere in user folder AppData\Roaming\DisplayCAL.
    With old & new profiles VCGT could be inspected, with log files you/other people can find which calibration is loaded in VCGT when you perform a “profile only” task.

    #16363

    Florian Höch
    Administrator
    • Offline

    The process works as Vincent described. Note that calibration will be (and needs to) temporarily reset to linear during output levels detection. This does not affect the characterization measurements.

    #16364

    Alex Sikorsky
    Participant
    • Offline

    For all the versions described by Vincent – to all “OR”, the answer is “No” … why the curve has changed, I understand. The change occurred in the version when there were three different ‘TRC_*’ and a part of the compensation was redistributed to them. I consistently went through all possible profiling options, having spent the time and looked at how everyone behaves and what happens. As an option to see and compare (‘VCGT’) profiles in folders. – This is also not necessary to do, because the program where I conducted the observation is able to save this data for further comparison, as well as compile the profile if necessary to make corrections.

    But your remark that the curve is reset, and after calibration is set again – important, I myself came to this conclusion, but I needed confirmation that this is exactly what happens. On the measurement does not affect, affects the final result, when the correction curves in LUT reappear

    #16365

    Florian Höch
    Administrator
    • Offline

    On the measurement does not affect

    Yes it does. You cannot add the calibration afterwards and expect the result to be correct.

    I’m still unclear what your goal is, i.e. which calibration you want to use for “profile only”. In a screenshot above, you used a specific previous profile and cal file, so the resulting profile will have exactly that calibration in its vcgt. This can be different from using the current videoLUT contents (current videoLUT contents are likely those of the profile you installed last if you haven’t changed them deliberately). To use current videoLUT contents, you have to select “<current>” under settings.

Viewing 15 posts - 1 through 15 (of 16 total)

You must be logged in to reply to this topic.

Log in or Register

Display Calibration and Characterization powered by ArgyllCMS