For what it's worth, I tested my Sage vs. my Forma using a densitometer. I placed a quartered screen black/white pattern on both displays and checked at four spots in each quarter. Using the readings from the 8 black and 8 white points, I came up with a contrast ratio of 16.4:1 for the Forma and 19.6:1 for the Sage which comes pretty close to the 15% increase in contrast ratio claimed by Eink for their Carta 1200 screens. Both are slightly better than the 15:1 for the Forma's Carta screen and the 17.25:1 for the Sage's Carta 1200 screen (extrapolated from the 15% improvement claimed by EInk).
I also reversed the pattern and no significant changes were seen.
By contrast, one article I read years back claimed that a mass market paperback book had a reflectance of 65% and a contrast ratio of ~8:1. Though since the author was associated with E Ink when they were still in Cambridge, that might have shaped some of his conclusions.
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