When I view a picture on a Windows monitor that is calibrated, which steps are involved?
* Simple monitor (like my built in on laptop):
- If I have the monitor ICC profile set in Windows, I have understood that the os only tells applications the character of the monitor; ie, it is up to the application in use, to do necessary correction to the picture passed to the monitor.
- But when reading discussions, I get the impression that the graphic card adjusts the picture presented on screen according to the profile (LUT).
- Question: Does an application/ os use the graphic card to adjust RGB values (by some LUT), or does the application do it by itself? Or is it mixed …
* Advanced monitor:
My external AdobeRGB capable EIZO monitor displays my pictures from PhotoShop, LightRoom, Affinity Photo and similar, well. That is expected as the monitor hardware does appropriate adjustments.
- Meaning the graphic card just passes the picture through ?
So, basically; when can one really trust what is displayed? And what are the steps involved when displaying colors on the monitor?
Going back to the OT's questions, when you calibrate/profile a monitor (probably using Color Navigator if it's an Eizo monitor), two quite distinct processes happen: calibration and then (surprise, surprise) profiling.
Calibration means adjusting the monitor to a specific state. With most monitors, you can adjust only white point (e.g. colour temperature) and tone response curve (e.g. gamma). These result in settings for the LUT in the video card and alter the characteristics of the monitor, which means it changes the characteristics for all programs. For monitors with in-built hardware 3D LUTs, the colour space can also be calibrated, but only to colour spaces that are narrower than the monitor's native colour space (i.e. within its native gamut). In practice this is relevant only for wide-gamut monitors. I mean: who would want a monitor colour space even narrower than a normal (roughly sRGB) colour space?
Except for monitors with hardware LUTs (like NEC, Eizo, Benq and some Dells) the colour space is what it is, and can't be altered by calibration.
After calibration, the software profiles the monitor. That means measuring the colour space, white point and tone curve. Those measurements go in a profile. A profile just describes the characteristics of the monitor. Confusingly, the calibration info is also usually put in the profile (even though it's not really anything to do with the profile) and goes in the vcgt field in the profile. After calibration/profiling, the calibration/profiling software sets the default monitor in Windows to that newly-created profile.
At boot up, a gamma loader or similar program loads the vcgt info into the LUT in the video card or monitor. That means all programs - whether colour managed or not - "see" the changes of calibration.
Colour managed programs (only) look up the default monitor profile (or more than one if there is more than one monitor) and use that for colour management. That is, they converts pixel-by-pixel from the image colour space to the monitor colour space before output to the monitor.
Colour managed programs should display the correct image colour. Non-managed programs will get the calibration, but won't map images colours to monitor colour space, and won't generally get the right colours. This applies even to an Eizo monitor whose colour space can be calibrated. For example, if you calibrate the monitor to Adobe RGB as you say, if you view an sRGB image using a non colour managed viewer or browser (e.g. W10 photos app, or IE or Edge) then the colours will be over-saturated, as sRGB image data is sent to an Adobe RGB monitor without colour space conversion.