The question “What is the best tablet with ereader screen” may mean something else for the person who presented it as it means to our editorial team. In any case, we take the question as a challenge, and try to explain what is possible today and what requires more technology development. The question also hints at an exciting product concept that we simply must explore further.

No commercial product that we aware of has a screen that could switch between two modes: LCD and E ink. The display technologies are so different that they require their own hardware at the moment. The tiny dots (pixels) in LCD color displays emit light in order to present information that people can view. LCD screens must be constantly refreshed for retaining the information visible on the display.

E ink screens – often used in e-readers and price tags in shop shelves – don’t emit light, but microscopic tiny particles inside tiny cells on the screen adjust their position to form letters and images. E ink display is refreshed only when information on the screen needs to be updated, for instance, when a book page is turned.

So, if you want a tablet with color and E ink screen, the product must have two separate displays. Although we are not aware of any tablets or ereaders that have two screens, mobile phones are (or have been) available with both LCD and E ink screen. For instance, YotaPhone introduced a few two-screen models, but the company didn’t survive in the tough mobile phone market.

A screen is often the most expensive component in a mobile device. If a product has two screens, it also complicates software and adds hardware – all adding to the price.

Perhaps the original question addressed another case? Since LCD screens can show colors, they can be set to display black-and-white or shades of grey only. If a person who is reading an ebook on a tablet turns the LCD screen into black-and-white mode, does that make a tablet an ereader?

No, it doesn’t. The LCD screen still emits light and constantly refreshes the screen. This is something people who worry about blue light maybe interested in. Recently, more evidence has been published on the safety of blue light. Also optometrists recommend rationing screen time with activity and rest periods, rather than worrying about the blue light.

There is still one more option to explore. What if an ereader device had a color screen? The screen technology would be similar to E ink, but it could display colors without emitting light? Recent industry news is that a color E ink screen is coming to e-reader products during 2020.

The color screen E ink technology is called Kaleido. It is capable of displaying 4096 colors. Don’t hold your breath, though. Color E ink screens have been in development for about 10 years, but the technology hasn’t been good enough for commercial products yet. The Kaleido screen must be seen live before judging it, but it looks like it doesn’t exactly have vivid colors.

A video demonstration by Onyx Boox shows the live color E ink screen on a product the company is planning to launch: