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Comment by crazygringo | Hacker News Reader

I'm curious why?

My understanding is that if you simply turn the brightness on an LCD display down to whatever the ambient brightness is (hold a piece of white paper next to the screen to compare), that there is zero eyestrain over what paper or e-ink would be.

Have you tried that? It feels strange at first -- as if the screen feels "dim" -- but then once you realize the contrast is just fine, you get used to it within minutes.

(And in case you have a problem with glare, just get a matte screen covering, easy peasy.)

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One nice thing is that you can see the displayed image by whatever light you want. Outside, inside, firelight, incandescent, vapor-arc, [built-in] LED... whatever.

I have a feeling that the contrast is also better under dim light, but no evidence, so I might be full of shit. And LED/LCD tech is obviously getting better in this regard.

Still, if there was a good implementation of an E-ink monitor with a refresh rate good enough for text editing, I'd easily drop 10k on it. I spend hours every day writing and reading and my preference for staring at E-ink displays over all other technologies is no contest.

You can't really do this because the contrast becomes way too low for comfort. It could become feasible with OLED, but that comes with a preference for dark mode anyway (due to the well-known issues with OLED endurance) which inherently addresses eyestrain.

I believe this is a misconception, and I'm not sure where it comes from.

Blacks on LCD screens really are quite black -- and if you dim your screen to ambient brightness, they obviously become even blacker.

This is why I said it takes a few minutes to get used to -- it "seems" dim or low-contrast, but only because you're comparing it with the ultra-mega-high contrast your monitor has when turned up to high brightness. When compared to paper (where "black" ink often isn't that dark anyways, particularly with matte finish like most books), the contrast is certainly just as good.

You could drive down the backlight intensity to try and keep the contrast the same, but then the whole screen would start flickering like crazy due to PWM - and that's assuming that the hardware even supports being driven down to that level! It can also be hard to recover if you accidentally drive the backlight down too much or even turn it off altogether!

I'm not sure what you mean -- both my MacBook and iPad let me reduce the backlight intensity to very little, and there's zero "flickering like crazy" at all.

What devices have this problem? I've personally never encountered it on any LCD screens I've ever owned.

> both my MacBook and iPad let me reduce the backlight intensity to very little

I don't agree - I have a long-standing complaint that Apple doesn't let you reduce the brightness on their devices enough! I would definitely want to lower the brightness on my MacBook Pro more at night if I could.

On my Mac I've even used third-party software that overlays the screen with a semitransparent black square to darken it, but that reduces contrast. On my iPhone I use the accessibility filter to darken the screen.

I assume they've limited the minimum brightness due to PWM flicker.

So... yes, I've experimented with that on the Mac too (I think it was "Shady" or something?), so you certainly can.

But that doesn't reduce contrast beyond what's inherent in reducing brightness -- the blacks when the backlight is at minimum power in a dark room are black. You seriously don't get blacker than that in any practical sense that is relevant to the human eye, certainly not on the high-quality displays MacBooks have.

I don't know what you are trying to say with the word "contrast", but a utility like Shady does exactly what you're asking for -- reduces brightness below the minimum -- with zero negative optical side effects. It seems that whatever you're expecting it to do (dimmer but better contrast) is literally a physical impossibility.

Probably a fluorescent-backlight LCD rather than a LED-backlight LCD ?

EDIT : Huh, looks like both are susceptible to the issue, but diode-crystal has it actually worse than fluorescent-crystal ? https://www.infobyte.hr/blog/134/ccfl-vs-led-screen-backligh...

LED brightness is usually modulated with PWM which involves turning them on for shorter periods of time. Eventually it appears to flicker.

The GP is probably thinking of low-end TN panels, which really do have poor contrast, combined with significant variance in off-axis brightness and color reproduction, further exacerbating the problem. These were extremely common until only recently, with even Apple's pre-Retina MacBook Airs using them.

A modern IPS panel, however, can offer much higher contrast than most e-paper displays, and should offer a comparable experience to e-paper if set to an appropriate ambient brightness and color temperature. This last part is key, because otherwise, you end up with a harsh, bluish cast in residential lighting scenarios.

Most TVs and monitors can have their color temperature set manually, but the only OEM I'm aware of that is doing this automatically right now is Apple with its "True Tone" displays.

There is a complete difference between a light emitting screen and a light absorbing screen. Even backlit Kindles are much nicer to read on than iPads of the exact same "brightness".

Its not about how dim it is. Daylight is orders of magnitude brighter than any lightbulb out there and has different levels of color wavelengths. Dimming a screeen actually does the opposite of what you would get reading eink outdoors, even in the shade. This is why TV's and projectors have such a hard time reaching the required brightness levels to be seen in broad daylight.

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