Comment by GuiA | Hacker News Reader

Comment by GuiA | Hacker News Reader

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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 of hardware that will measure your display’s colors and tell you how off they might be.

The author bought a piece of color calibrating hardware that was meant to be open in design and work with Linux, as presumably he wants to support these efforts.

But he encountered a bevy of problems, ranging from packages not updated in a while to things that just plain don’t work as documented, and got frustrated.

Understandable, since on macOS or Windows with proprietary hardware, this would have been a 5 minute process. The author is sad and frustrated that the open source alternatives aren’t there.

Displays also drift over time. So even if you have a professional display calibrated at the factory it needs to be recalibrated a minimum of once per year with 6 months being preferred in a professional environment.

This is true with even the highest quality color critical displays like we use in film/tv color correction ($5-$50k+ for 25" panels).

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”

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.

Because light is analogue, our eyes are analogue and the light conditions of the living room is analogue, the paper where images are printed is analogue and so on.

It is physically impossible to get an unique colour space across all surfaces.

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.

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.

A digital communication channel allows faithfully sending an image to the display. Turning that data into colored light is another thing.

Standard values of the voltages, currents, timings etc. that are applied to LEDs, liquid crystal pieces and other electronic components of the display in order to get the desired colors are only a starting point; a calibration that measures the differences between devices and compensates them is needed because of manufacturing and accidental differences.

To add to all the comments here: the range of physical colors a monitor can display intentionally also differs (a low gamut, sRGB gamut, or one of several wide gamut standards). The video pipeline sends just 8 or 10 but values at the display, but the actual color seen can differ dramatically.

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