MobileRead Forums - View Single Post - LCD vs. e-ink: The eyestrain debate

Kris777 · 11-09-2011, 09:00 PM

I like these comments made by Russ Wilcox, co-founder E Ink :

While LCDs are adequate for reading, E Ink was invented and engineered for the best possible reading experience. Your readers might like to hear about a few technical factors that are not well known and contribute to the difference:

1. Ambient brightness
Over the years many people have told me that reading an emissive display is bothersome to them while E Ink is not.

I think one reason is that as you read, your eyes skip along the lines of text, dwelling for a fraction of a second on small groups of words. Your eyes are constantly moving ? hundreds of times per minute. So it is very important that your eyes be able to refocus on the surface of a screen within a split-second.

Emissive displays are ill-suited for this. While you are reading a book, you see a lot more than the screen. Your field of vision is wider than the page alone and your eyes often glance off the page. With a backlit screen, every time your eye switches from a bright screen to the dimmer ambient room, your eye muscles must make an adjustment. And the more adjustments, the more chance for eyestrain.

With paper or E Ink, the page is the same brightness as everything else in the room. Your eye needs less adjustment effort to go back and forth. You can see and understand information more immediately. Paper is the ultimate "glanceable" display and that helps improve comprehension and maximize reading speed.

2. No parallax / closer to the eye

Have you ever gazed at a calculator display and noticed a bit of a shadow? That is parallax. The same thing happens on your emissive LCD. The white color is actually coming from a backlight behind the LCD; the black color is coming from a shadow cast by the liquid crystal material in the middle of the LCD glass sandwich. So black and white are different distances from your eye. This degree of shadowing changes with the viewing angle. There are also two sheets of glass and multiple polarizer films between your eye and the white background, which creates a slight feeling of separation between screen and real world.

In an E Ink display, the electronic ink contains black and white particles that are both moved physically by electrophoresis to the front of the display. So both black and white are exactly the same distance from your eye. Furthermore, both are at the front pressed up to the top layer of glass. This greatly contributes to the feeling that the information is printed on the top of a page.

3. Less glare

All E Ink display surfaces are treated to be matte like a printed page. Most LCDs are not. This is not an obvious feature when you buy the product, but it makes a huge difference to legibility in some settings.

4. Same contrast across the entire page

Although modern LCDs have greatly improved their viewing angle uniformity, there is still a detectable difference in contrast ratio across the page. These differences in contrast make it just a tiny bit harder to resolve images as your eye skips along the page. As the screen gets larger or closer to your eyes, as with a handheld book, this angular difference is increased.

5. No aperture ratio loss

The pixels on LCD screens do not have a full aperture ratio, because each pixel must be separated by a black border. The border hides the underlying transistor and separates the areas of the color filter. There are actually 3 sets of borders per pixel, since color LCDs have RGB subpixels. This all adds up to tiny black gaps between each pixel. As LCDs reach higher resolutions there are even more dead gaps as a percentage of viewing area.

E Ink screens have a 100% aperture ratio. There is no black mask and no black border between pixels. When two neighboring pixels are white on an E Ink screen, the pixels merge to form a solid block of white. Therefore the blacks and whites on an E Ink screen are uniform, again improving image quality.

11-09-2011, 09:00 PM	#35
Kris777 Banned Posts: 1,767 Karma: 2520493 Join Date: Oct 2008 Device: Nexus 7, jetBook-Lite, jetBook mini, Toshiba Thrive, JETBOOK COLOR	I like these comments made by Russ Wilcox, co-founder E Ink : While LCDs are adequate for reading, E Ink was invented and engineered for the best possible reading experience. Your readers might like to hear about a few technical factors that are not well known and contribute to the difference: 1. Ambient brightness Over the years many people have told me that reading an emissive display is bothersome to them while E Ink is not. I think one reason is that as you read, your eyes skip along the lines of text, dwelling for a fraction of a second on small groups of words. Your eyes are constantly moving ? hundreds of times per minute. So it is very important that your eyes be able to refocus on the surface of a screen within a split-second. Emissive displays are ill-suited for this. While you are reading a book, you see a lot more than the screen. Your field of vision is wider than the page alone and your eyes often glance off the page. With a backlit screen, every time your eye switches from a bright screen to the dimmer ambient room, your eye muscles must make an adjustment. And the more adjustments, the more chance for eyestrain. With paper or E Ink, the page is the same brightness as everything else in the room. Your eye needs less adjustment effort to go back and forth. You can see and understand information more immediately. Paper is the ultimate "glanceable" display and that helps improve comprehension and maximize reading speed. 2. No parallax / closer to the eye Have you ever gazed at a calculator display and noticed a bit of a shadow? That is parallax. The same thing happens on your emissive LCD. The white color is actually coming from a backlight behind the LCD; the black color is coming from a shadow cast by the liquid crystal material in the middle of the LCD glass sandwich. So black and white are different distances from your eye. This degree of shadowing changes with the viewing angle. There are also two sheets of glass and multiple polarizer films between your eye and the white background, which creates a slight feeling of separation between screen and real world. In an E Ink display, the electronic ink contains black and white particles that are both moved physically by electrophoresis to the front of the display. So both black and white are exactly the same distance from your eye. Furthermore, both are at the front pressed up to the top layer of glass. This greatly contributes to the feeling that the information is printed on the top of a page. 3. Less glare All E Ink display surfaces are treated to be matte like a printed page. Most LCDs are not. This is not an obvious feature when you buy the product, but it makes a huge difference to legibility in some settings. 4. Same contrast across the entire page Although modern LCDs have greatly improved their viewing angle uniformity, there is still a detectable difference in contrast ratio across the page. These differences in contrast make it just a tiny bit harder to resolve images as your eye skips along the page. As the screen gets larger or closer to your eyes, as with a handheld book, this angular difference is increased. 5. No aperture ratio loss The pixels on LCD screens do not have a full aperture ratio, because each pixel must be separated by a black border. The border hides the underlying transistor and separates the areas of the color filter. There are actually 3 sets of borders per pixel, since color LCDs have RGB subpixels. This all adds up to tiny black gaps between each pixel. As LCDs reach higher resolutions there are even more dead gaps as a percentage of viewing area. E Ink screens have a 100% aperture ratio. There is no black mask and no black border between pixels. When two neighboring pixels are white on an E Ink screen, the pixels merge to form a solid block of white. Therefore the blacks and whites on an E Ink screen are uniform, again improving image quality.