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Comment by mhb | Hacker News Reader

I don't understand the graph of Irradiance vs. Wavelength for an ebook vs. print book. It looks like the print book was read in the dark? Help.

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It looks at the emitted energy from the screen.

The ebook emits directly, a foot from your face.

The paper book is reflected energy, at a rather higher reflectance and a rather lower energy.

It's amazing how dim a light you can read a paper book in vs an e-ink ereader.

Photons are photons, reflected or not.

So what prevents the ebook to lower the brightness of backlight to match the energy of the reflected light from a paper book?

(For e-ink ebook readers, can't they just be read without backlight, with just reflected light?)

Short answer is "They don't go that dim." I don't know if there's a technical limitation or it's just not done, but the "1%" frontlight (most e-ink displays are frontlights, LCDs are just awful for every aspect of reading) is quite a bit brighter than reflected.

E-ink readers absolutely can be read without backlight, and I've experimented with that vs the frontlight for the past few months. The older ones (my Kobo Aura) require a lot of light to be readable, but are readable without much trouble by kerosene lantern. The newer ones (Kobo Clara HD) are better, and require less light, but all of them require an awful lot more light than a paper book.

> (For e-ink ebook readers, can't they just be read without backlight, with just reflected light?)

Usually you need more reflected light to read from e-paper because of worse contrast.

A lot of people over the age of 40 or even 35 are going to have trouble reading a physical text from a comfortable distance in light dim and warm enough not to affect one's circadian rhythm. Though I see your points and agree with aspects of this piece I also really struggle to see how a dim light close to your face is objectively worse than lighting your entire room in order to read a book and think extreme statements about the harms of LED/Blue light/Screens tend to more often than not generate unnecessary anxiety in a world where LEDs and screens are inevitable for many/most

I'm in that age group (post author) - over 40.

I've experimented with self-lit screens vs lantern lit {books, e-ink screens} vs overhead incandescent bulb lit {books, e-ink screens}. The results are clear. LED lit screens are awful for my sleep.

But we disagree on a major point about LED screens being "inevitable." That is, certainly, the current cultural default. No question. But I also know a lot of people who are rejecting that default - partly due to their own experiments with "But how do I sleep?"

I don't think LED lighting is a force of nature, by any means. I think it's a human decision, that we can agree to or not. And if it's a problem after dark, as I argue it is, then we ought reject it in favor of things that don't mess with our sleep and overnight melatonin levels.

I guess my point is that although the LED lit screen was awful for your sleep, that's not to say it's an awful thing for all. When it comes to insomnia there is always a psychological component, which makes the wind-down process before sleep incredibly important. As someone who works in accessibility I can tell you that it is a fact that reading physical texts at night is going to be a big issue for a lot of people over 40 and most people over 60. It's better that they are allowed to continue with their nightly reading habit with control over font size, contrast, brightness than to say "hey figure something else out, tablets at bedtime will kill you!". the alternative is likely to eventually be an even larger screen anyways or a more physically or cognitively stimulating activity.

> A lot of people over the age of 40 or even 35 are going to have trouble reading a physical text from a comfortable distance in light dim and warm enough not to affect one's circadian rhythm.

This, so very much this. I no longer read physical books. I need more light to do so, I need readers (which give me a headache). eBooks are the best thing for me, and allow me to keep on reading where I think I'd have largely stopped by now if I could only have paper books.

For those of you too young to have used a public library much as an adult, they often carried many of the popular titles, as well as some specifically-requested ones, in large print editions precisely for their older patrons.

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