Should You Buy a Color or Black and White E Ink? Let's talk about Screen Brightness

(This article is an English translation of my original work, written on July 3, 2021. Here is the original script)

Are you considering buying an E Ink device? I believe many people do a lot of research online before purchasing one, whether it's reading bloggers' sharing articles or checking relevant information on social media. Therefore, you probably have some understanding of the differences between various E Ink technologies and the E Ink devices from different brands. The common points of hesitation for most people before buying an E Ink device boil down to the following:

1. Is it better to choose a dedicated e-reader or a multi-functional E Ink tablet?
2. Which brand of E Ink device is better?
3. Which size of E Ink device is better?
4. Is it better to choose color or black and white?

Points 1 to 3 have a lot of good resources available online  for everyone's reference, so I don't want to repeat them. My series of articles will only focus on point 4 for explanation, because I think my views on color E Ink might be different from many people's opinions online, so I can provide different ideas here for everyone. This article will first focus on explaining the brightness of E Ink screens, which is a common point of comparison and discussion.

Differences in Screen Brightness

I believe many people already know that color E Ink screens appear slightly dimmer than black and white E Ink screens because most of them use Kaleido Color filter array (CFA) technology to display colors. The white background isn't as white, and the contrast is also slightly worse than black and white. This point is often listed as a disadvantage of color E Ink and is often used to dissuade people who are thinking of buying one. Also, because the screen is slightly dimmer, many people subjectively believe that color E Ink cannot be used without the front light to make the visual effect look similar to black and white E Ink and to make the colors more vibrant. Moreover, some users also feel that prolonged use of the front light will still cause eye strain and discomfort. Therefore, they feel that color E Ink is currently not worth buying, and they don't recommend it to many beginners.

If you have already absorbed the above information from other sources, then I think you should definitely read on to absorb some different viewpoints before carefully considering whether a color device is what you want. First, you can take a look at the following photo:

Both of the e-readers above have their front light completely turned off. Guess which one is the color E Ink reader?

In the photo above, the one on the left is actually the black and white e-reader Kindle Paperwhite 3, and the e-reader on the right is the color Hisense A7 CC. Seeing this might surprise you, as it might not align with your existing understanding. Shouldn't the screen brightness of a black and white screen be brighter? Indeed, when photographed from the same angle, the color screen does appear darker. However, we can often make an e-reader reflect more ambient light by adjusting the angle of incidence light from the light source or the angle of the e-reader. Please refer to the following video:

Sometimes by adjusting the angle, the difference in the intensity of reflected light on the reader's surface can be very large.

It's important to know that color filters do absorb reflected light, but the degree of absorption is about 10-20%, not 50-70%. Therefore, many times, we can compensate for this absorption by simply allowing the screen surface to capture a bit more ambient reflected light. So, to make it appear as bright as the black and white screen, you usually don't need to turn on the front light; just adjusting the angle is sufficient. For a more detailed explanation regarding the front light, please refer to this article: "The Myth of Front Light on Color E Ink".

Someone might argue that this comparison isn't fair, and if we turn the black and white e-reader to the same angle, it will be brighter than the color one. But the question I want to ask is: 'When buying an e-reader, is your goal to prioritize eye comfort or simply to compare devices?' The real question isn't about achieving the whitest or brightest screen, but rather identifying the range of lighting in which your eyes will feel comfortable while reading.

The intensity of light that human eyes can accept is an absolute range, not a relative feeling. Relative comparisons aren't very meaningful. Moreover, why is a black and white E Ink device used as the benchmark for comparison? Especially since the brightness on black and white E Ink screens varies among different brands.

The color brightness of area A and area B is actually the same, but the surrounding environment can give the illusion that area A is darker. Therefore, we should be concerned with whether the current brightness is suitable for us, rather than relying on relative feelings.

Disadvantages Are Also Advantages

We know that the surface of a black object absorbs most of the light, while the surface of a white object reflects most of the light. Human eyes don't get damaged in darkness (I don't think anyone wakes up with damaged eyes after sleeping), but they can be damaged by strong light. The whiter and brighter the surface, the more light it reflects. Therefore, although black and white E Ink has a bright white background, your eyes also receive relatively more reflected light. The color filter on a color E Ink screen is actually like sunglasses, absorbing some light (including blue light), so relatively speaking, it's better for eye protection.

In this world, the disadvantages of many things are also advantages: black and white E Ink can be used in darker environments, but color E Ink can be used in brighter environments. This is somewhat similar to how wearing sunglasses indoors might feel too dark, but under the bright sun, you might find that wearing sunglasses prevents the sunlight from being so glaring. To be honest, sometimes on a very sunny day when I sit by the window to read, I actually find the white background of my 13.3-inch Max Lumi too bright, while the white background of the Nova 3 Color is more comfortable at this time. The color filter on a color E Ink screen just shifts the suitable range of light intensity; it doesn't reduce it. In situations where you truly cannot adjust the surrounding light source and angle, then you can turn on a little bit of the front light. If you have concerns about turning on the front light on an E Ink screen, you can refer to this article: "Does turning on the front light on a color E Ink screen negate its eye-friendly purpose?"

Conclusion

When using a reflective screen, you should pay attention to whether the ambient light is sufficient, just like reading a paper book. If you find the screen too dark and your eyes strained when using a color E Ink device in a certain environment, it also means that using a black and white one in the same environment would also be a bit difficult and not much better. Therefore, I think the slightly darker screen is almost a completely negligible factor when purchasing a color E Ink device. However, color E Ink also has another disadvantage, which is the issue of lower screen resolution. This is a more important aspect to consider when actually making a purchase, and I will share my analysis of resolution in my next article, "Resolution of E Ink devices: Dithering is also a key factor".

When reading a paper book, you also need to adjust the angle from time to time to get better light.

About the Author

Jack Black

Driven by a passion for physics, science, and engineering, I seek to leverage my medical experience to advance human health and environmental sustainability.

If you liked what I wrote, feel free to support me. It'll give me more motivation to create. Thanks!