Quote:
Originally Posted by Spycrowsoft
However: most real printed media also uses a very limited number of colors on usually a 150 or 300 DPI dot matrix.
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It's far more complicated than that unless you are thinking of 1930s budget colour on wood pulp. The image is about 150 dpi to 300 dpi, but the dots to print the shades of C Y M & blacK are much higher resolution. For example if a 600 dpi colour laser is doing halftone is about 100 lpi. Colour lasers and basic inkjets use the CYMK system.
Books with colour use more inks and higher resolution dots.
Even cheap newsprint at only 85 lines per inch is effectively higher resolution than many tablet LCD and eInk colour because of how the half-toning system works
https://en.wikipedia.org/wiki/Halftone
RGB is very problematic for eInk (colour addition) because it inherently has only about 4000 tones and lowers the resolution. It's like LCD, in that it uses a colour filter on a monochrome panel. But an LCD can do more than 260 shades of grey and do it over 100 faster per pixel than eink. The mono eink is basically white or black per cell and using clever tricks to get about 14 shades of grey (which is slower).
The inverse colour subtraction (CYM) uses layers of pigment and works somewhat differently (aecp aka Gallery 3), so is very slow (1.5 second refresh). It's brighter and/or more saturated but still poorer than decent paper print, LCD and OLED. An as yet not invented CYMK technology of bistable display with eink properties is needed.
Don't hold your breath for a decent colour eink. We once thought Mirasol was the answer (10+ years ago) and while possibly better than RGB filters on mono eink, proved to be poorer than claimed. One ereader (two brands) was made for the Chinese market and sank without trace.