E-Ink vs. real Paper - Contrast and Brightness

[scheichxodox]

Hi folks,

Today I've read about the new E-Ink technology. It will offer 12:1 contrast ratios (up from 7:1). That sounds great, it nearly doubles the contrast ratio. But to have a comparison, what contrast ratio does paper have? Someone here in the forum wrote, that old paper turns yellow-ish and you also lose contrast. So for a comparison it seems to be important which kind of paper you use - is it recycled paper, is it new white paper on which you print with your own printer, is it a book or is it a magazine.

How do you measure the differences in readability between real paper and E-Paper? Contrast ratio? Brightness? Also there seems to be a difference with the plastic layers above the actual display and if it has touch support or not (Sony PRS-505 and PRS-600). Though both displays should have the same contrast ratio, the PRS-600 looks darker and seems to have a worse contrast ratio.

In 2007 E-Ink announced the second generation of their epaper technology Vizplex, which had the following enhancements:
* Typical Switch Speed: 740 ms (previous: 1200 ms)
* Peak Switch Speed (monochrome): 260 ms (previous: 500 ms)
* Brightness (reflectance): 40% (previous: 32-35%)
* Greyscale levels: 8 (previous: 4)
I found nothing about a change in contrast from the first to the second E-Ink generation.

Also do you have any information about the contrast and brightness of other technologies (Sipix, Mirasol, Liquivista, Pixel Qi)?

Thanks in advance for your answers

Greetz

Scheich Xodox

[cmdahler]

You were right when you said it depends on the paper. Another very important factor in determining the readability of the text is the number of pixels per inch the system is capable of displaying. 12:1 is generally in the neighborhood of a typical quality hardback book, but again, there's no set number to reference as it depends on both the ink and the paper the printer used. I've seen numbers quoted before that range from around 10:1 up to 15:1. 12:1 is going to be a serious improvement over the 7:1 of today's displays, certainly. 300 dpi will provide sharpness that is more or less the same as you'd see in a typical book or magazine, so until display manufacturers are able to hit this level, the text is still going to look a bit "fuzzy" compared to the printed page. What you get with eInk (around 170 dpi) is generally far better than the pixel density of your average LCD display.

[Magnesus]

Originally Posted by scheichxodox

I found nothing about a change in contrast from the first to the second E-Ink generation.

There was literally none. I had a device with 4 colour Vizplex and now have with 8 colour Vizplex and there isn't any difference between the contrast of those two.

[Dylrob]

Originally Posted by Magnesus

There was literally none. I had a device with 4 colour Vizplex and now have with 8 colour Vizplex and there isn't any difference between the contrast of those two.

Vizplex = second generation eInk. The number of shades of gray related to the display controller, not the display itself.

Being the owner of a PRS-500, which did have a first generation display, I can say that the Vizplex screens are noticeably brighter. Of course brightness ≠ contrast.

[scheichxodox]

So what does a better contrast ratio mean? Does it mean that the background gets brighter or does it mean that the displayed text gets darker or is it a combination of both? Is contrast more important than brightness? That means, would a display with a darker background with better contrast be also better to read than the one with brighter background?

Greetz

Scheich Xodox

[Magnesus]

Originally Posted by scheichxodox

So what does a better contrast ratio mean? Does it mean that the background gets brighter or does it mean that the displayed text gets darker or is it a combination of both?

"The contrast ratio is a measure of a display system, defined as the ratio of the luminance of the brightest color (white) to that of the darkest color (black) that the system is capable of producing." - http://en.wikipedia.org/wiki/Contrast_ratio