I'm aware of a lot of anecdotal evidence in favor of e-ink displays being easier on the eyes than normal LCDs in some way, my own personal experience included, but I will happily admit I'm wrong if there are studies indicating otherwise.
I like my Kindle and DIY e-ink weather display but I'm not religious about it. I wouldn't be shocked to find out it was just a weird placebo thing because it's different.
[1] suggests that LCD even increases processing speed compared to e-ink
[0] https://pubmed.ncbi.nlm.nih.gov/22762257/
[1] https://bop.unibe.ch/JEMR/article/view/2338/3534
there's a study from Havard concluding "e-ink is 3 times better for eye health than LCD" but it feels rather dubious from the claims (blue light stressing more the retina... like i couldn't use a glass or apply a filter on my screen), light intensity (again...), in-vitro study and who funded the study (a great e-ink screen producer) -> https://sid.onlinelibrary.wiley.com/doi/10.1002/jsid.1191
i probably read hundred books since i sold my e-reader and moved to my smartphone. i really like having a single device. battery is fine. physical books with images still rocks but maybe becuse i don't have a tablet :)
(i.e. setting the "frontlight" brightness to 0% on a Kindle, which would also eliminate color temperature control other than room ambient light).
It does seem hard to believe that e-ink + a reflected frontlight would be any easier on the eyes than an LCD backlight (particularly since it's probably also using PWM). But an e-ink display on its own at least removes an additional light source pointing directly at the eyes, which could provide a potential mechanism for different effects on the eyes/brain.
Not really, since LCD/OLED aren't an additional light source, but absorb and thus replace the ambient light that would be coming from their direction.
I started as a teenager with cathodic tubes, which were killing my eyes and bringing daily headaches; moved on to LCDs which stopped the headaches but still tire my eyes significantly (some of them literally make me cry after a few minutes); and then found eInk and it's so much better, I will definitely move to that once prices of large color monitors at 60hz get into my price range. I honestly don't care about power draw one bit.
Quick experiment to show the effect: Go into a room with low 2700K or lower-temp lighting. Take an LCD, set its colour temperature same as the external lighting, then display an all-black screen. Since the screen is displaying #000, the software colour temp adjustment can't do anything, and you'll see the screen as emitting blue light, the colour of its backlight.
OLEDs don't have this issue, which makes them great for night-time use when configured properly, but they also generally use low-frequency PWM dimming on low brightness.
Don’t they actually have to over power the reflection you would see with the screen off?
I frequently stumbled upon the assumption that a LCD screen is pulsed and flickers and that makes all the difference as E-Ink is more steady. (Artificial lightsources can also flicker, but with reflection it evens out)
In (old?) theory too fast for the eyes to notice, but I surely notice a difference.
Their brightness can also be conveniently, even subconsciously controlled, by how they are held.
LCDs can be dimmed and brightened, but matching the E-Inks “response” in both brightness and contrast over a high range of ambient lighting would be difficult. Probably impossible without an LCD specifically designed to do that.