[coder543]

does light have any other intrinsic properties besides spectrum/wavelengths and intensity (EDIT: properties that vary based on the light source alone)? It doesn't matter if it came from a backlight or reflection, the electromagnetic waves are still electromagnetic waves. If the color spectrum is unpleasant, it's possible to use Night Shift or other features to shift the spectrum. If the intensity is unpleasant, just turn down the brightness.

[romed]

The problem is LCDs have much worse objective performance as the backlight diminishes. E-Ink has tragically bad contrast of 15:1, but it maintains that contrast ratio in low lighting conditions. LCD panels rely on high brightness for their contrast. At very low brightness, even the best LCD display has poor contrast.

OLED displays have a different problem; they have so much noise at low brightness that the image falls apart. Still, I think a monochrome OLED display is what the person who wrote this article actually wants. It would have better performance in every respect to E-Ink, and it doesn't sound like their application requires E-Ink's low power.

[coder543]

I have used both LCD and OLED smartphone displays at incredibly low brightness in pitch black rooms for a long time, and I have to completely disagree.

On the other hand, E-Ink is amazing in sunlight, where smartphone displays can't get sufficiently bright.

[singularity2001]

Which smartphone displays can you set to 'incredibly low brightness'? all iPhones and Androids I've used are like bright flashlights when the lights are switched off.

[coder543]

It's all relative. I don't own a single flashlight that can be set dimmer (or anywhere close to as dim) as my iPhone XS Max is at minimum brightness on a white page. If the XS Max is showing mostly-dark content, the amount of light emitted is really tiny at minimum brightness because of that OLED display.

On the various Android devices I've owned, I've used a useful app called Screen Filter that adds a translucent layer on top of all apps to dim the screen beyond the artificial manufacturer-imposed minimum brightness, which worked especially well on OLED Android phones, but also LCDs worked fine too.

[orbital-decay]

Presumably, all or most Xiaomi phones. I've never used one for long, but the lowest backlight level in those I tested (Redmi Note 2, Mi A1, RN5) was comparable to the level 2 or 3 of the Kindle Paperwhite frontlight. (level 1 is a failsafe option since the Paperwhite has no physical buttons, it's not meant for reading, being too dark even for a pitch black room)

That said, I don't think reading in poor lighting conditions is a good idea for your eyes, no matter the technology.

[Obi_Juan_Kenobi]

You can use an app to reduce the brightness further. I've been using Twilight on Android, and it does indeed get much dimmer. You will certainly lose some image quality/performance, but it's very nice for viewing in a dark room.

[jseliger]

This is actually a reply to @Romed:

OLED displays have a different problem; they have so much noise at low brightness that the image falls apart. Still, I think a monochrome OLED display is what the person who wrote this article actually wants. It would have better performance in every respect to E-Ink, and it doesn't sound like their application requires E-Ink's low power.

My understanding too is that OLEDs can have "true black" pixels that emit no light at all. For "dark mode" style screens, this is a huge benefit, because the majority of the screen may simply be turned off. Conventional LCD screens still send current to each pixel, but the "black" is simply tuned to a dark frequency, rather than being altogether off.

[romed]

Yes, an unpowered LED emits no light. But an OLED that's barely on, for example at uniform 1% grey looks like crap because of the noise. People describe this as a "texture" or "banding". It's the consequence of trying to drive millions of individual semiconductor devices to the same emissive power. At higher brightness you can't notice the noise.

[tinus_hn]

Lcd screens are transparent and selectively block the light from a backlight. They can’t show full black because they can’t completely block the backlight.

[fermienrico]

Yes, I know what electromagnetic waves are. I found your response very off-putting.

The question is whether the intensity is discussed in the link. My point was that the discussion is more to do with the frequency of light than with intensity.

[pvg]

does light have any other intrinsic properties besides spectrum/wavelengths and intensity?

Sure, think of things like polarizing filters, lasers, etc.

[coder543]

Lasers are just a method of creating light of a single wavelength. The light itself from the laser is still defined by its wavelength and intensity.

Polarization is just related to the orientation of the electromagnetic waves, and it is a property I didn't mention, you're correct. I don't think it really matters here, though. It's kind of like which direction you shine a light, except whether the waves are all oriented the same way or not. I would almost argue that it's an extrinsic property since uniform polarization is almost exclusively the realm of external things like filters, not the light source itself.

Your "etc." is a little vague.

[fermienrico]

I really don't understand what your point really has to do with the original discussion.

Ok, light can be described by its intensity and wavelength. So what? Can you tie this to the original parent post?

You can break it down further - intensity is just the "number" of packets (photons). So, really, light is just frequency and travels at max speed (C) because photons are massless.

Where are we going with this discussion?

Edit: I am not able to respond to you below so I am responding here. You're right on this one - it doesn't matter what the originating source is, light is light whether it is reflected or emitted.

[coder543]

The argument is that since the light is the same, it can't have different effects. Reflected light cannot be inherently healthier than light from an LCD.

[pvg]

You were suggesting light doesn't have any other 'intrinsic properties' and that's not the case - phase (a laser is not just a monochromatic light source) and polarization come to mind. Whatever it is you're trying to argue, 'light is just wavelength and intensity' is not a sensible starting point.

[fermienrico]

Also, if we go a little deeper, then intensity is really not intrinsic property of photons themselves. Photons radiate through space and are carriers of electromagnetic force. They have momentum but no mass. Its energy and momentum is a function of frequency (or wavelength). Furthermore, they also have spin angular momentum which is truly intrinsic as it does not depend on frequency.

So, the saying that light is just "intensity and frequency" is naive and flat-out incorrect.

[coder543]

It isn't possible to make light that is faster or slower than other light, so does it matter that some other property is derived from this constant* ? A property derived from one variable and a constant property is perfectly logical to refer to as intrinsic, since it's always exactly linked to one intrinsic property. Splitting hairs there doesn't make sense.

Which things can a light source vary, besides wavelength and intensity? It's easy to define intensity in this context as the photons being emitted per period of time. This isn't like trying to define the intensity of sound as an intrinsic property, when it really depends on a number of actually intrinsic variables.

*within a given medium, which is external to the light... which means it won't change based on reflected vs LCD.

[coder543]

Is it not sensible, though? People are trying to argue that light from a backlight is inherently more dangerous than reflected light. The easiest way to dispel this notion is to establish that the light from a backlight is just light like any other, which it is. At most, it varies in spectrum and intensity. Polarization is affected by filters outside of the light source. The phase that's hitting your retina varies entirely based on irrelevant things like when the light source was turned on and how far away it is.

Starting by pointing out that intensity and wavelength are the only intrinsic properties is a great starting place.

You still haven't pointed out any additional properties that have any bearing on how your retina is affected. I was wrong the say that there were no other properties, since we can endlessly discuss the quantum nature of light or how it experiences no flow of time since it travels at the speed of light or all sorts of other properties...

but none of these things change based on the light source. Light is light, except for the intensity and wavelength. Unless we're willing to consider things which could affect reflected light just as much as they could affect emitted light, since they're the same thing. Light.

[pvg]

Light is light, except for the intensity and wavelength.

I'm not sure why you're so set on this obviously inaccurate thing and are now moving the goalposts to stuff about retinas and what the meaning of 'intrinsic' is. All I'm saying is both light and especially the perception of it are fairly complicated. You can just read up on it like everyone else instead of building a weird messageboard logic hill fort.

[coder543]

Yet you fail to point out the inaccuracies... I'm not moving the goal posts, I'm just clarifying where they were to begin with. You pushed them as far as you could within the wording of my original message, instead of taking the "strongest plausible interpretation" of my original message.

[snovv_crash]

Light from lasers is also phase coherent. This is in sharp contrast to LED, incandescent etc.