Based on supplementary material "We utilized a professional photographic inkjet printer (ImagePROGRAF PRO-1000, Canon), equipped with 11 ink cartridges and a chroma optimizer". Not your typical office printer but nowhere near as exotic as you might expect.

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lupire 3 days ago | parent [-]

How special are the inks in the cartridge, though?

	▲	froh a day ago \| parent \| next [-]
		? they are not four but twelve different (!) base colors. they are calibrated and are very light proof i.e. degrade much slower over time, "look the same" after years. what's your background in understanding how printing works?
	▲	actionfromafar 3 days ago \| parent \| prev \| next [-]
		I have to assume it used inks available from Canon. Making your own inks is a research project on its own, so my guess is that would have been mentioned.
	▲	Almondsetat 2 days ago \| parent \| prev [-]
		They are special in the sense that they are calibrated and QA'd for professional use