Monday, September 10, 2012

Black and White E-readers are Here to Stay

Like Rock and Roll, Black and White is here to stay, at least according to the recent NY Times article. The article was paraphrasing Jeff Bezos. However in an interview after the event at which the NY Times was reporting, Mr. Bezos seemed to say a more reasonable, “black and white displays will be around for a while to come”.

To be sure, a lot of trade-offs must be made in going to a color display. They are necessarily more complex, but more importantly for mobile devices, they consume multiples more power and the current generation of LCDs has no sunlight viewability capability at all. The first portable computers were monochrome. The Data General One (lunchbox configuration) had a monochrome LCD that was barely visible at all. The loss of brightness to do color made color out of the question then. The first notebook configuration PC, the Grid, had a red on black plasma screen. Plasma had no color capability then and the power consumption of that display made the Grid much more of a transportable than a mobile device. The original Compaq transportable had a monochrome CRT (green on white). Color CRTs were available and the power consumption did not matter as it was a plug-in device, but there was no color content in the PC world. This also meant that most monitors where monochrome as well being either green on black or amber on black.

The selection of a colored font (green or amber) rather than white on black was made for human factors reasons. Black on White, the paper paradigm, was also not used. In the eye, the cones (the color receptors) are in the center of the eye while the rods (the black and white receptors) are concentrated in the periphery of the eye. This arrangement is for very good primal reasons; in the dark you still want to have good peripheral vision to spot any sort of threat. In brighter environments you rely on your color vision. In an office environment using colored font is easier on the eyes. Color also provides chromatic contrast in addition to the brightness contrast of a white on black font. Pen on paper was inherently monochrome as adding color added significantly to the complexity and hence expense of reproducing handwritten documents. When the printing press was invented, the use of color blossomed but monochrome still tended to rule for cost constrained documents such as newspapers and paperback books. The image above is from a Gutenberg Bible.

Similar to the invention of the printing press, electronic word processing pioneered development of color. Information such as emphasis and misspellings were highlighted with color. This initial development of color content did away with monochrome computer monitors and subsequently with monochrome notebooks. In the early development of LCDs, yields on LCD arrays were low and yields on LCD color filters were even lower. A combination of increased yields and lower raw materials costs lead to color and monochrome LCDs equilibrating in price in the early 1990’s. Monochrome still had a substantial power consumption advantage. The color filter in an LCD disposes of about 2/3rds of the light coming from an LCD and powering the display is generally about half of the power consumption of a mobile device. So going to a color display meant about a 1/3rd reduction in batter life. However, once color was cost competitive with monochrome, color notebooks went from being about 20% of the market to about 95% of the market in about 9 months. The consumer was clearly stating their preferences.

Notably, Apple was the last to get rid of its monochrome notebook line. Steve Jobs had been an investor in a start-up that was developing a new kind of display technology. A friend of mine that saw an example said that it was monochrome and actually quite advanced for its time. However, perhaps it did not have a path to do color. Early on, some were writing Plasma off until it developed a means to do color. In any case, perhaps Mr. Jobs involvement with developing a monochrome display lead to the company holding on for monochrome for too long. When there was wide availability of color based software, color content, the transition to color in mobile computing was swift and absolute.

As noted above, color LCDs still have their issues with non-existent sunlight viewability and high power consumption as compared with digital paper such as the E-Ink displays in some Kindles. Although, I’m sure the E-Ink folk are gratified by the NY Times headline, I’m just as sure they are not going to stop working on color. However, Mr. Bezos may be right in that it might be a while. When the transition of notebooks from monochrome to color happened, color ranges were limited and color resolution was only 8 bits (that is 8 bits spread between red green and blue, not 8 bits per color)…. And, there was no need to do video refresh rates. Today, consumers have gotten used to color fidelity that is as good as their eyes can discern. A technology that only generates pastels might not be worth the power hit. Beyond that, there is the challenge of doing video refresh rates in a bi-stable display.

The statement that “Black and White is here to Stay” may be a bit overblown. Consumer’s preference for color is natural and overwhelming. They were unanimously willing to give up 30% of battery life to get color in notebooks. Perhaps they were willing to give even more. However, the power advantage of the paper-white display is much more than that.


  1. This blog is intentionally published with white text on a dark background. The words may not jump off of the page but I do feel that it makes the image of the screen more visually interesting. In black text on white, you are essentially looking at the holes in the image. Also without any chromatic information, I think that black text on a white background just looks very plain. It is, of course, the pen and paper paradigm because that is what paper and ink could offer, not that it was the best.

  2. I should also add that ubiquitous wireless charging could significantly reduces the importance of power consumption as well driving lower utility for bi-stable devices.


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