Does the voyage backlight emit blue light (prevent melatonin production)? thanks

[kocoman]

Does the voyage backlight emit blue light (prevent melatonin production)? thanks

[HarryT]

It doesn't have a backlight; eInk screens are opaque, and hence can't be backlit.

The front lighting LEDs are nominally white light, but there's a wide variation between devices. Some are a lot warmer in tone than others. Just "pot luck" what you end up with, I'm afraid.

I seriously doubt, though, that blue or otherwise, you'll be exposed to enough of the light to make a difference. It's a very small device, and not a terribly bright light.

[krazy4katz]

White light probably has blue in it, but without knowing the exact wavelength and how much, it is difficult to tell if it will affect melatonin production. I don't know if any studies have been done in humans that would answer that question.

Although the device is front lit, you must absorb the light, otherwise you couldn't read on it (at night).

[SteveEisenberg]

The Voyage screen is not a mirror. Wouldn't the light reflected back be more determined by the characteristics of eInk than of the light?

I don't know for sure -- just asking.

[JSWolf]

Originally Posted by kocoman

Does the voyage backlight emit blue light (prevent melatonin production)? thanks

That report was crap as they used FULL brightness for four hours.

Nobody would read in a full dark room at full brightness. Heck with my H2O in full dark, I read with the front light at 4%. That is nowhere near as bright as an iPad at full brightness.

So just use what works for you and ignore that report that used unrealistic settings.

[krazy4katz]

Originally Posted by SteveEisenberg

The Voyage screen is not a mirror. Wouldn't the light reflected back be more determined by the characteristics of eInk than of the light?

I don't know for sure -- just asking.

Good point! It would be determined by both, I think. First, what wavelengths of light are hitting the the screen (determined by the color spectrum of the light source). Second, which wavelengths are absorbed (looks black if all are absorbed) vs. which wavelengths are reflected back.

[krazy4katz]

Originally Posted by JSWolf

That report was crap as they used FULL brightness for four hours.

Nobody would read in a full dark room at full brightness. Heck with my H2O in full dark, I read with the front light at 4%. That is nowhere near as bright as an iPad at full brightness.

So just use what works for you and ignore that report that used unrealistic settings.

What report are you referring to? I would be interested in reading it.

Thanks.

[SteveEisenberg]

Originally Posted by JSWolf

Nobody would read in a full dark room at full brightness.

The same light level was used for tablet reading and paper book reading. Because the sleep medicine docs, in their journal article, used the word "dim" to describe the room lighting, those who wish to disbelieve have an out. But the actual described ambient florescent lighting wasn't what the average person would call dark, or even dim. If it was, the experimental subjects would have refused to read the paper books.

I think a fairer (although hardly devastating) criticism is that the authors were engaging in spin when describing the ambient lighting as dim, perhaps to discourage focus on the role of the cool-white fluorescent lights.

Originally Posted by krazy4katz

What report are you referring to? I would be interested in reading it.

http://www.pnas.org/content/early/20...90112.full.pdf

http://www.pnas.org/content/suppl/20...01418490SI.pdf

[meeera]

You can stop fretting about your Kindle - just keep the lighting down to a reasonable level, not blaring. If you're particularly worried, have some room lighting so you can decrease the brightness further.

The study used iPads on full brightness for four hours, to get ten minutes delay in sleep onset. We discussed it in detail on another thread.
The frontlit Kindle, using reasonable indoor settings, puts out a tiny fraction of that light.

[meeera]

And for a visual - here is a dimmish room, midsummer midday with louvre blinds (lots of light leak - I could read a paper book), showing an Aura at a comfortably readable setting (IRL - I realise the photo is harder to read), and an iPad Mini on full brightness with auto brightness turned off. The iPad (used in the study) is significant bigger, and by the time you square that, it's blaring a lot more light into your eyes than even is shown in this picture.

[kocoman]

Usually I read ebook when I can't fall asleep, was wondering if reading ebook with that "blue" backlight prevents me from falling asleep.

also does reading in the dark (with little night light) damage the eyesight? thx

[haydnfan]

White is red, green and blue mixed in equal measures, so yes the light contains blue. As JSWolf said the "research" is bogus. I once asked a biologist about light and sleep disruption, and she said it was light in general at night that can disrupt sleep. The weak light from a kindle or a tablet will hardly matter compared to say having all of your lights on at home or working late in an office with bright overhead fluorescent fixtures.

[dordale]

Originally Posted by kocoman

Usually I read ebook when I can't fall asleep, was wondering if reading ebook with that "blue" backlight prevents me from falling asleep.

also does reading in the dark (with little night light) damage the eyesight? thx

Again--if you're referring to an e-ink screen, as Harry pointed out earlier, they are not back lit. They are front lit. meaning the light comes from LEDs situated in the front of the screen, it's not being lit from behind like LCD screens.

Personally (based on my personal experience only not any studies), I don't like reading on my iPad before I go to sleep. On the other hand, I enjoy reading on my Kobo Aura HD and Kindle PaperWhite (both front lit e-ink screens). To me, reading on the Aura and PW in a dark room is similar to using an external light source.

[arjaybe]

Stop hijacking kocoman's thread. OP didn't say anything about a "report." Your argument is on another thread. You know who you are.-)

[krazy4katz]

Originally Posted by kocoman

Usually I read ebook when I can't fall asleep, was wondering if reading ebook with that "blue" backlight prevents me from falling asleep.

also does reading in the dark (with little night light) damage the eyesight? thx

There is still a lot of debate regarding control of circadian rhythm in humans, which is the concern here. There are special light detecting proteins in the eye that respond to blue light and signal to your brain to control circadian rhythm. This is what controls your sleep/wake cycle as well as many other functions in your body. However, there are other light receptors in the eye — the ones that you consciously see with — that may also play a role — that is a debate that is still ongoing. Regarding reading in the dark, that will not damage your eyesight in the sense that your vision will degenerate.