Hacker News Reader

Comment by chris_overseas | Hacker News Reader

An E-reader seems like a bad analogy given they're usually reflective rather transmissive displays. Wouldn't any backlit display technology (such as most computer monitors) make for a better example?

View on HN

The author is trying to evoke electroluminescent backlit displays. It's a very specific kind of display technology and it's become fairly uncommon, but for maybe four to ten years it was ubiquitous.

I'm trying to think of an example... the Timex Indiglo watch? A lot of displays with that weird, creepy green or blue glow. Oh, some Palm Pilots and other early handhelds.

I don't actually think e-readers with EL displays are common but some e-readers have a similar color and it's easy to see being confused.

It was a really big deal when they became mass market (90s, I think?) and were the peak of “cool” at the time. But they’re absolutely horrible for energy consumption.

Here’s an example: https://upload.wikimedia.org/wikipedia/commons/b/b8/66Charge...

They compete mainly with the fixed-segment monochrome LCD display market. I’ve seen some in multicolor as well.

Casio comes to mind when coming up with EL devices for example. The classic G-shock I have on my wrist right now touts a "Electro Luminescent Backlight", though I rarely use the light.

There was a Japan-only Game Boy Light that was the form factor of the Game Boy Pocket but with an electroluminescent display. I have one, and to this day it's one of my favorite handhelds. It males grayscale games are absolutely gorgeous in the dark.

Surprisingly, it has a very decent battery life - 20 hours without the backlight, 12 with.

Indeed. I can imagine they use the same basic chemistry, but I struggle to imagine they're displaying English words. Perhaps somewhere in the depths one of a million has the collected works of Shakespeare on its back, prison-style.

Not really, LED’s work by directly emitting light or not. LCD’s work by sitting between the light source and you and blocking that light.

Squid’s have significant internal reflection so this really is much closer to e-ink displays with a light on the edge.

…but does not manufacture public opinion?

E-readers are definitely more like dead tree pulp whereas an IPS panel screen on a device like iPad would be closer analogy. :-)

Is that true of modern e-readers? My original Kindle was a gray background on gray text dark mess, but Kindle White uses LEDs at the screen edge directed through a light guide to come from behind the text. Not that most people don't just use the Kindle app on an OLED or LCD screen smartphone nowadays anyway. Considering e-readers unlighted at this point would be like considering handheld games unlighted because the original Gameboy wasn't.

> through a light guide to come from behind the text.

What does that even mean? The nature and the underlying physics of the light hitting the cornea of your eye doesn't change or depend on how or where the rays of light originated. I know a lot of e-reader folks try and upsell 'behind the text' but that's not how it works.

Light always has to reflect or radiate off of a surface from the front.

It's a description of the mechanism that delivers light of unchanged nature and physics to your eyes.

>Light always has to reflect or radiate off of a surface from the front.

And in the case of the Kindle, the light reflects off of the pigment layer from above, rather than radiating directly from a light source behind the pigment layer. GP's comment just contains what amounts to a typo. The light guide is in front of the text, not behind it.

The light on the Kindle does not come from behind the text. The lightguide is in front of the text. It directs the light from the edge LEDs down, where it reflects off the text and back up through the lightguide out to your eyes.

Here is a detailed tear down of the Kindle optical system: https://arxiv.org/abs/1605.05174

I clicked on the article hoping for information on how e-ink displays are illuminated and was (not unsurprisingly) disappointed, but this paper absolutely saves it.

It's pretty cool to see how they did it and thinking about how it could maybe be DIYed. Do you happen to know whether anyone has attempted such a thing before? I'm not totally clear about the chance of success here, but the 2 main components, clear plastic and a roughed up surface, seem generally DIYable. I very uncertain about the quality, however (since I'm not sure what exact shape the rough spots need to have, I'm basically limited to whatever a laser can make). My greatest fear is that the light won't actually go down onto the screen, but directly into the user's eyes, I guess.

> My original Kindle was a gray background on gray text dark mess

That was the best tech in my opinion though, closer to how a book works. A backlight makes my eyes tired, and I definitely don't want to use a Kindle app on an LCD display, what would be the point?

Kindles don’t use a backlight. They are semi front illuminated, more like shining a light on your book. The light can also be turned off

Yes, a much better version of the “light” in those classic “indestructible” Casio watches.

I still find the unlit or separate-booklight-lit grey kindle to be a lot easier to read than a self-lit white kindle.

And while a current kindle's light can be turned off, you control the light through the touchscreen interface, so if you have the light off and it's dark, you have no hope of turning it on, so you have to just always leave it on. It's a really stupid system.

you're right, it's a clunky example.

I guess the author must have a Nook Glowlight, otherwise i'm lost on example.

Reply on news.ycombinator.com