The display industry is in a bit of flux, and display calibration activities are caught in the middle. In the legacy environment, the graphic card out was a key component. Communication is possible to nearly all displays using some level of the DDC 2.0 specifications. It is important to note that an ICC profile does not “calibrate” a display. A monitor profile is merely a container that describes the display properties to the color management system. Most modern displays have internal look up table capabilities as well as control of backlight…. I have never seen a native raw panel that didn’t have a typical gamma 2.2 profile built in. A wide gamut panel will necessarily have an input lookup table, a matrix or 3D out, followed by a display look up table. In general, use of the graphic card LUT is not recommended at all inmost modern calibration environments. If a display has an HDMI interface, the graphic card LUT is normally inaccessible because there are a number of assumptions about the display color management. The current processes generally calibrate the displays to a given color space and use a very simple ICC profile to describe the display setup. Many display vendors provide software that monitors the user interface adjustments and register the proper profiles based upon the user selections either based upon the display UI or a software application installed on the platform. As the industry moves towards HDR (high dynamic range) and Wide Gamut , calibration occurs in the display, not on the driving platform. The ICC profile is used as a container for other information in HDR systems in Windows 10. The current trend is that the internal graphics processor system is used for rendering such as games or 3D simulations. The actual calibration of the display occurs inside the display where there is significant processing for scaling and managing color space. Regards, Tom Lianza
On Jul 6, 2019, at 3:00 PM, colorsync-users-request@lists.apple.com wrote:
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Today's Topics:
1. FW: Monitor Calibration Question (Wayne Bretl)
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Message: 1 Date: Fri, 05 Jul 2019 13:24:44 -0700 From: Wayne Bretl <waynebretl@cox.net> To: colorsync-users@lists.apple.com Subject: FW: Monitor Calibration Question Message-ID: <004a01d5336f$b0ff5e90$12fe1bb0$@cox.net> Content-Type: text/plain; charset=UTF-8
-----Original Message----- From: Wayne Bretl <waynebretl@cox.net> Sent: Friday, July 05, 2019 1:23 PM To: 'Louis Dina' <lou@loudina.com> Subject: RE: Monitor Calibration Question
I don't actually KNOW the answer, but it seems to me that having the monitor write to the graphics card LUT when you make a color temp adjustment ON THE MONITOR (not on some driver software) would not work, as the next time you boot up, the monitor profile would re-write the LUT. Also, if changing settings on the monitor actually rewrote the graphics card LUT, it would destroy the calibrated LUT until it was reloaded by bootup. [Unless the graphics card had two successive LUTS, one for the profile and one for the monitor hardware setting.]
I believe LCD's must have internal LUTs, because their native transfer function is nothing like CRT gamma to begin with. So, this is an obvious place to make modifications for in-monitor color temperature settings, not back in the graphics card.
Not knowing the number of bits precision in these various possible LUTs, I have generally assumed it's best to set the monitor to the preset for the color temperature I want (or the closest available) and then apply the colorimeter/spectrophotometer calibration/profile process to make minor changes in the graphics card LUT.
Maybe someone who has thought this through more thoroughly can comment.
-Wayne
-----Original Message----- From: colorsync-users <colorsync-users-bounces+waynebretl=cox.net@lists.apple.com> On Behalf Of Louis Dina via colorsync-users Sent: Friday, July 05, 2019 8:51 AM To: colorsync-users@lists.apple.com Subject: Monitor Calibration Question
I have a question about where the calibration adjustments are made in low to medium-end LCD monitors (not high end models, like Eizos). I have an aging Dell U3011 and a Viewsonic VP2365WB, which are 'okay' monitors, but certainly not what I'd call high end.
With our old CRTs, we were able to adjust white luminance, black luminance, white point, etc, inside the CRT monitor itself using the monitor's controls. These preliminary adjustments did not alter the information in our video cards, leaving them in a pristine, straight-line condition. Then our profiling software made minor adjustments to give us a neutral grayscale with even steps between levels, and wrote this to the VLUT of the video card and to the vcgt tag in our profiles. Unless choosing Native White Point, this usually meant reducing the gain of one or two of the RGB channels.
With consumer level LCDs, it was always my understanding that the ONLY analog control on the monitor was the brightness of the backlight (once again, I'm not talking about higher end LCDs). It was also my understanding, that if we altered the white point using the monitor's RGB gain controls, or selected a preset (such as 5000K, 6500K, 7500K, etc), these changes were reflected in the curves written to our video cards and not inside the monitor itself.
I am questioning whether I am mistaken here. Do most consumer LCD monitors have the internal circuitry and graphic processors to make these changes independent of the video card in our computers? And if so, is it better to try to achieve our targets using the monitor controls?
My approach to calibrating and profiling my monitors was to leave the LCD monitor's RGB gains all set to 100%, contrast set to factory default, adjust the backlight control to achieve my desired white luminance, then let the profiling software make all the necessary adjustments to achieve my targets for white point, white and black luminance, gamma, etc.
Thanks for any feedback.
Lou _______________________________________________ Do not post admin requests to the list. They will be ignored. colorsync-users mailing list (colorsync-users@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/colorsync-users/waynebretl%40cox.net
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