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Notes on Color #9: Color Calibration

In January, as part of the preparation for digital painting training, I calibrated my laptop display and my pen display. Yet in April I realized that images look quite different on my laptop, on the pen display, on my phone or on others' devices.

After hours of research, trail and error, I managed to learn more principles and calibrated my hardware and software. Here are some notes:

1. Colorimeters are not spectrometers. Instead of measuring the full (visible) spectrum, the main goal is to simulate a standard observer (with three color receptors), or XYZ values.

2. Due to #1, there are assumptions made here and there to cut down the cost without hurting the quality too much. However an important aspect is the type of monitor (e.g. WLED, WLED+phosphor, GB LED,  RGB LED, OLED etc.).  The chracteristics of each type is diffrent, mostly on the "base spectrum". The calibration may look off if the wrong correction matrix is used. Note that old colorimeters might not support newer display technologies.

3. The default "Photos" app in Windows does not support embeded color profiles in images. I'm now using XnView MP.

4. Chrome (and likely other browsers) usually support embeded color profiles, however it'd be safer to simply convert the image to sRGB when upaloaded to the Web. The reason is the color profile may be stripped or incorrectly processed by the websites.

5. Chrome by default uses the default color profile (for the current monitor) of the system. It might make sense to change it to sRGB.

6. After trying a few calibration tools by the colorimter vendors (e.g. SpyderExpress, i1profiler), I still prefer DisplayCAL. Note that it still makes sense to install the vendor software, such that DsiplayCal may import correction data.

7. According to the author of DisplayCAL, ICC v4 is not necessisarily better than ICC v2 in practice. And v2 is way more comptable for now.

8. It might be necessary to verify and recalibrate the displays every month.
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