Quote:
Originally Posted by Katsunami
Back-light: In a back-lit device, the lights are built into the screen, and they're behind it. They light it from inside to outside. Therefore, the screen does not reflect any light, as a front-lit screen or a book page would; the screen itself emits the light. In a back-lit device, the screen *is* the light source.
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Except that this is not how backlighting or frontlighting works, at least as implemented in modern LED-backlit LCDs and LED-frontlit eink displays.
LCD: The light source is in the bezel, and projects into a substrate layer that lights up behind the LCD panel via reflection of the LED light. This provides a more or less uniform brightness (on poor-quality displays you can often see light bleeding from the bezel where the LEDs are mounted, or have hotspots and dark spots). LCDs the light this way because they're transparent, and are basically just tiny little color filters.
Eink: The light source is in the bezel, and projects into a substrate layer that lights up in front of the eink panel via reflection of the LED light, in almost exactly the same way as with an LCD. In the case of eink, the substrate must be in front of the panel because eink is opaque. Putting a light behind it would be pointless.
In either case, you're not looking directly at the light. You're looking at light that has been reflected multiple times (compare this to old CRT displays, modern plasma displays, or AMOLED displays, where each pixel directly emits light as opposed to filtering reflected light). Not that it matters, because that makes absolutely no difference. Don't believe me? Okay, go grab a flashlight and a mirror. Turn on the flashlight and look directly at it. Blind, right? Once your vision returns and the pink and green blobs subside, point the flashlight at the mirror and look directly at its reflection. It still blinds you. Reflecting light does not give it any sort of magic properties.
What really makes reading more comfortable is the size and shape of pixels, not the type of light that you're using. A piece of paper printed on an inkjet printer has round "pixels" and anywhere from 300 to 600 of them per inch. On most average desktop and laptop monitors, pixels are square and there's only around 100 of them per inch. The bare minimum for comfortable reading is around 150-160 square pixels per inch (fewer if the pixels are non-uniform, like on eink, since that naturally creates smoother letter shapes). Modern mobile devices (phones, tablets) are mostly above 200ppi these days, some reaching well over 400ppi. Eink devices are also increasing (the Nook Glow's 6" 600x800 screen has 167 ppi, while the Kindle Paperwhite's 6" 768x1024 screen has 213ppi).
TL;DR: Pixel density is much more important than lighting method.