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Open Source Color Management Is Broken

lieberbiber.de

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Re: Open Source Color Management Is Broken

#11

Post by seba_dos1 »

> Except that they only set it for the primary output. Turns out if you have multiple displays, the profile for the first one is put into the _ICC_PROFILE X11 atom, but the profile for the second one in the _ICC_PROFILE_1 X11 atom, for the third display in the _ICC_PROFILE_2 X11 atom, and so on. It’s just that nobody seems to do this.

Sounds like an easy thing to fix. I'd suggest the author to try and make some patches - don't know about GNOME, but KDE is pretty friendly and easy to contribute to.

Re: Open Source Color Management Is Broken

#13

Post by semi-extrinsic »

_trampeltier wrote: post #10
GuiA wrote: post #4

Earlier quoted context omitted.

If you do any professional color work, you want a color calibrated display. This ensures that the colors you see on your screen will be the same as the ones on your designer colleague’s screen, and the same as the ones that come out of the printer’s factory, for instance. Higher end displays are already pretty decently calibrated out of the factory, but if you want to be exact you will need to buy an external piece o…

I could understand you have to calibrate a display if the connection between PC and display would be analog. I don't understand it in the digital age.

I also have this question. I mean, the ones and zeros that get sent over your DisplayPort/whatnot cable for some specific color in your favorite color space should be identical for all computers everywhere. Why don't we then just calibrate the monitors themselves, rather than the whole OS?

Re: Open Source Color Management Is Broken

#14

Post by grzm »

_trampeltier wrote: post #10
GuiA wrote: post #4

Earlier quoted context omitted.

If you do any professional color work, you want a color calibrated display. This ensures that the colors you see on your screen will be the same as the ones on your designer colleague’s screen, and the same as the ones that come out of the printer’s factory, for instance. Higher end displays are already pretty decently calibrated out of the factory, but if you want to be exact you will need to buy an external piece o…

I could understand you have to calibrate a display if the connection between PC and display would be analog. I don't understand it in the digital age.

The display at the end of it is an analog device. The calibration confirms that the actual light coming out of the screen is an accurate representation of what the digital information thinks it should be.

Re: Open Source Color Management Is Broken

#15

Post by dljsjr »

_trampeltier wrote: post #10
GuiA wrote: post #4

Earlier quoted context omitted.

If you do any professional color work, you want a color calibrated display. This ensures that the colors you see on your screen will be the same as the ones on your designer colleague’s screen, and the same as the ones that come out of the printer’s factory, for instance. Higher end displays are already pretty decently calibrated out of the factory, but if you want to be exact you will need to buy an external piece o…

I could understand you have to calibrate a display if the connection between PC and display would be analog. I don't understand it in the digital age.

It's not about the signal it's about the physical display.

Displays aren't calibrated at the factory. To use an LED-backlit display as an example, not every single LED in the world is created equally. Not every LED is going to give off the exact same wavelength for the same current value.

Extrapolate this out to all the other components and this is the reason that your monitor has built-in physical controls for changing RGB/contrast/brightness values to begin with.

Calibration accounts for this.

As for why ICC profiles are used instead of just changing settings on the monitors, the OSD options usually don't offer enough fine-grained control to get things just right. Display makers are typically targeting main-stream consumers so they provide simple adjustment controls.

Re: Open Source Color Management Is Broken

#16

Post by lostapathy »

semi-extrinsic wrote: post #13
_trampeltier wrote: post #10

Earlier quoted context omitted.

I could understand you have to calibrate a display if the connection between PC and display would be analog. I don't understand it in the digital age.

I also have this question. I mean, the ones and zeros that get sent over your DisplayPort/whatnot cable for some specific color in your favorite color space should be identical for all computers everywhere. Why don't we then just calibrate the monitors themselves, rather than the whole OS?

We essentially are calibrating for the monitor’s version of the color not being 100% accurate. Yo’re right, in a perfect world the monitors would just be correct from the factory.

In practice, monitors change color over time (much mire common in ccfl backlit monitors, i think) and even shift with brightness, so we have to do it “at runtime”

Re: Open Source Color Management Is Broken

#17

Post by jhasse »

seba_dos1 wrote: post #11

> Except that they only set it for the primary output. Turns out if you have multiple displays, the profile for the first one is put into the _ICC_PROFILE X11 atom, but the profile for the second one in the _ICC_PROFILE_1 X11 atom, for the third display in the _ICC_PROFILE_2 X11 atom, and so on. It’s just that nobody seems to do this. Sounds like an easy thing to fix. I'd suggest the author to try and make some patch…

GNOME isn't.

Re: Open Source Color Management Is Broken

#18

Post by dljsjr »

semi-extrinsic wrote: post #13
_trampeltier wrote: post #10

Earlier quoted context omitted.

I could understand you have to calibrate a display if the connection between PC and display would be analog. I don't understand it in the digital age.

I also have this question. I mean, the ones and zeros that get sent over your DisplayPort/whatnot cable for some specific color in your favorite color space should be identical for all computers everywhere. Why don't we then just calibrate the monitors themselves, rather than the whole OS?

Monitors aren't often calibrated from the factory or they are calibrated to be "subjectively" nicer looking, e.g. high contrast and slightly cool white balance to account for show-room floors.

In addition to that the built-in options for configuration are often very simplified and have a coupling. Low resolution control plus simplified options means that you often can't dial in perfect color reproduction. Hence ICC profiles.

Re: Open Source Color Management Is Broken

#19

Post by theatrus2 »

mark-r wrote: post #12

If you write the calibration info to the video LUT, why does software also need to know about it? Isn't your monitor displaying perfectly calibrated sRGB at that point?

This is assuming all the content is sRGB, which is not a safe assumption especially if you care about color management to begin with.

Re: Open Source Color Management Is Broken

#20

Post by seba_dos1 »

Accacin wrote: post #7
gsich wrote: post #3

Earlier quoted context omitted.

The author cries about being not able to boot from the USB stick and that his ColorHug2 might be broken.

He wrote a pretty detailed blog article explaining his issues and how he got around them, this is all very useful information to someone who is looking to do something similar. Spending €100 also isn't an insignificant amount, and for that price I would expect what I'm buying to work properly.

I don't understand that attitude, that's a pretty low price for a niche open hardware device.
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