back to article Electronic ink: The whole story in black and white

Electronic books are popping up everywhere, but in the quest for colour it's worth remembering that ink isn't just used to print books. Every time El Reg covers electronic books we get questions about why such devices aren't colour yet, and what's so great about electronic ink compared to other screen technologies, not to …


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  1. Si 1

    Is there much point to colour?

    Seeing as most books are just black text on white paper, where does the need for colour arise from anyway? If it's to deliver better versions of newspapers with pictures, etc, then surely a web browser on a proper computer or smartphone is the answer? Plus those devices are backlit and can be used in the dark.

    The persistent-ness of an e-ink display is great, but with so many shortcomings and drawbacks I don't see why anyone wouldn't just read a book on a normal screen. I've read about 10 books on my iPhone, the reader program has auto-scrolling, customisable font sizes, custom text and background colours, auto-bookmarking, annotations, the ability to invert the screen in dark rooms, etc, etc. Having tried a few e-ink devices the dull display and weak interfaces are really nowhere near enough to convince me that I'd want to carry a bulkier, expensive device just dedicated to books around with me.

    It seems to me the e-ink devices are re-inventing the PDA wheel from a slightly different angle but without offering any advantages over devices that do much more.

  2. MonkeyBot

    Re: Does Colour Matter?

    Given that changing the colour can massively alter the readability, yes it does matter.

    Get the right colour for an individual and they can read from smaller fonts and so get more text on screen at once.

  3. Anonymous Coward
    Thumb Up

    You're entitled to a beer on me.

    One of the best articles I've read in a while.

  4. Jason Bloomberg Silver badge

    Cheap as chips

    "Motorola's latest enterprise handset that has one embedded in the battery: an innovation that the designers admit was driven by the incredibly cheap cost of the E Ink screen"

    Which rather begs the question why Kindle hardware and similar is so expensive.

    Far Eastern manufacturers have driven down the cost of small digital picture key rings / frames to almost give away prices but are presumably held back by the cost of traditional LCD for larger offerings. The core electronics should be similar regardless. Okay, Kindle may have additional connectivity and functionality, but it does begin to look like price gouging.

    I like the idea of e-Ink, expect it to become ubiquitous technology and only improve with time, but I'm not convinced in e-Books or the business models and practices which come with them.

  5. Anonymous Coward
    Anonymous Coward

    Reflective devices - RGB?

    Would'nt a reflective device use CMYK like printing?

    Anon - as my understanding of colourimetry should be better considering my profession.....

  6. Balefire
    Thumb Up

    The Readius - (almost) exactly how an eBook should be

    For me, an eBook reader should be like a newspaper. Well, apart from the brainless drivel content. A nice big viewable area, easily readable in ambient light. When you need to carry it, you can roll/fold it up and stick it in a pocket.

    It should also be easy to update and change the content no matter what OS you are using and with a large storage capacity.

    The current crop of eBook readers just haven't got the point - their screens are either small for portability, or big, for readability. But both are on inflexible screen media. Changing content if you are not using Windows based software is also a PITA - why can't they be accessible as a simple USB drive?

    It has been proven that eInk can be used on a flexible surface, so why no more devices like this?

  7. shadowphiar


    "refresh rate measured in seconds"

    Sir, I applaud your free-thinking approach to dimensional analysis.

  8. banjomike

    Not 'crippled'

    Not really 'crippled by its appalling refresh rate' if you are actually using the e-ink device to read a book. The refresh does not take any longer than turning the page of a book.

  9. Leo Maxwell
    Thumb Up

    It is surprising how people adapt

    I use an iLiad, for technical manuals (PDF)

    and ebooks.

    As close as you get to the real book without paper.

    For both, it is far superior to a Laptop, and it will only get cheaper and more versatile, and I can get my books almost instantly, and carry hundreds in a small pouch..

    I am not a fan of dead tree ware.

    Read Cory Doctorow's "content"

  10. EvilJason

    All i want is....

    A simple eBook that has the screen size of a standard paper back page, no wifi, no sound, no touch screens, no keyboards. A simple set of buttons, up down left right confirm and cancel and a menu button, also a left and right page button set some where easy to reach but out of the way for turning the page...think the buttons from a old game controller.

    Make it have a SD card slot be able to read a few formats that are not there own special brand and sell it all or whats left for under £100 then i would buy it. and so would everyone else.

    I dont want an ibook i want an ebook basicly an electronic book that does everything and only everything that a normal book does, i.e. display words and turn the page.

    Why make things complicated when simple will do...

    As for the price thing, remember when mp3 players where a couple of hundred pounds for a gig or two, compaire the price drop to what these ebooks will become.


  11. h 6
    Thumb Up


    Good article. But is it possible to put an e ink screen over an LCD/LED screen to mix power savings and color when you want it?

  12. Big-nosed Pengie
    Gates Horns

    Interesting technology

    with quite a few worthwhile applications. But for book readers and the like, damned if I can see any advantage over my old iPaq running Mobireader. It's got colours, it's backlit (so I can read it in bed at night without waking the Mrs) and, should I want it to, it can do other stuff. Yes, it's running the abominable Windwoes CE, but since I only use it for one purpose, it seems far superior to an e-book reader.

    I suppose the ability of e-ink to retain its state should mean virtually limitless battery life, but I think I'll wait until the backlighting problem's overcome, at least, before I think about it.

    Evil Bill - because he's a dick.

  13. Anonymous John

    Not so long ago,

    PCs and moble phones were greyscale. And I remember a friend of mine saying he couldn't see the point of a colour screen on a phone. I doubt that he believes that now.

    I'm quite happy with my Cybook now, but that won't stop me switching to colour. Not at first, but when colour ebook readers are well established.

  14. blackworx

    Title Schmitle

    "you can literally smash an E Ink screen and the shards will still display the last thing rendered"

    not true. every ebook reader with a cracked screen I've repaired (5 to date) has looked almost identical to a busted monochrome LCD.

  15. Gabor Laszlo

    But when

    will they finally implement programmable tattoos? Then we'll see some interesting advertising concepts.

    Also, E-ink powered billboards are long overdue (and just think how fast the Billboard Liberation Front will figure out how to hack them!)

    And wasn't there a 'where's my flying car' icon?

  16. Conrad Longmore
    Thumb Up

    Motorola FONE

    I bought an ultra-cheap Motorola FONE F3 just to see the e-Ink technology in action. The display is pretty crude, but it's kind of interesting if you just want to see a practical application in a small device.

  17. Gordon Pryra

    Re: Does Colour Matter?

    Yes of course,

    I want to be able to read an E-Book with the same affect as the printed word. I know colour will not help achieve that, well maybe "yellowing" the pages with an "age" filter or something?

    But I do know that the porn industry is the IT equivalent a war has on medical progress.

    Give them colour to play with and they will invest in the industry, the quality will increase and off the back of it, i will have a reader that mimics a real book (or as near as can be)

  18. Paul 4


    I take it the people saying "I dont see the pont" have never sat and read a full book on a display. It is down to flicker. Reading on a screen gives you eye strain and is difficult to do for long periods. eInk overcomes that (Infact that was the point).

    When people are talking about books on there iPhone I beleave even more that the are not doing anything more than flicking through a book on the train to work. I could never read a full novel like that, or a tecnical document, or anything that required consentration, but then I don't beleave that e-readers are the way forward for anything other than text books. There is something about books that people love. Even though people made the same claim about records, they were only around for 50 odd years where as books have been around in todays format since Gutenberg, arguably since papirus.

  19. Tom 7 Silver badge

    Oh dear

    @ MonkeyBot - you'd like to think that an e-reader would be able to zoom so still no need for colour.

    I've yet to see an e-reader that's anywhere near as useful as a book and anywhere near to replacing a PC- if I'm carrying my netbook about then I can read on that and I'm not carrying two lumps about.

    All I'd ever want in an E-book I'd want as a subset of what I want in a netbook . I might just consider a remote roll up screen that can bluetooth to the netbook/phone/desktop but I wouldn't want it a crippled PC weighing it down.

  20. Tony Hoyle

    Colour would help

    So you could get the white background rather than the dull grey we have now.

    eink displays are OK but the still aren't nearly as readable as a book - it's quite a strain to read them with a modest night light as black on grey is quite a poor contrast ratio. They win only in the exceptional battery life they have - I tried using an iphone once and quite apart from being *way* too small, the battery went flat in an hour... whereas I still haven't had to charge the reader

    They're also way too expensive - both the hardware and the books. £200+ for the hardware then books that cost more than paperbacks, very limited choice and multiple competing formats meaning even if you manage to find the book you're after there's a good chance it'll be in a format your reader can't read... before they get any kind of wide acceptance all of these problems will need to be fixed.

  21. Christopher Rogers
    Thumb Up

    I love it

    my eyes don't hurt after reading E Ink pages....

  22. Stu

    RGB vs CMYK


    You're absolutely right, RGB are the primary colours of light, i.e. additive colour mixing, whereby a self transmissive surface mixes up red and green, for instance, to produce yellow.

    OLEDs are true self-transmissive because the RGB elements emit light themselves. An LCD screen achieves the same effect by filtering out white light into R, G and B from a backlight behind them - may seem subtractive but its actually additive - if you enable only red and green filter elements in a pixel, then you're making yellow again.

    On the other side of things, cyan, magenta, yellow, blacK, (CMYK), much like the traditional red, yellow and blue, are combined on a surface to -subtract- light shone from elsewhere, i.e. sunlight or your room lighting, usually from above the reading surface. Subtractive colour mixing.

    ...that is, of course unless this FLEPia device works with a white back-light, in which case you use the RGB model again, it would act very much like a bog standard LCD screen albeit with non-volatile pixels.

    I can't say I've read anything about how the FLEPia works but I would argue a true colour e-ink display of the future would need to work with CMYK, or something similar, that is if you were to put it into the same technology category as todays black and white e-ink displays (no-backlight, cannot be read in low to zero light).

  23. Filippo

    Requirements for ebook

    1) Foldable/rollable. Large as a book when in use, small as a cellphone when not in use. If it's always large as a book, or if it's always small as a cellphone, then I don't want it.

    2) Properly designed interface. Hint: if you need to put so many buttons that requirement #1 cannot be satisfied, then you're doing it wrong. If it has a QWERTY, then I don't want it.

    3) DRM must be optional. If it doesn't read TXT, static HTML and plain PDF, then I don't want it. DOC and DOCX a nice bonus.

    4) USB port. If I can't copy files from a USB stick and/or read books directly from the USB stick, then I don't want it.

    5) Tough. If it can't stand being dropped from a desk, then I don't want it.

    6) No flicker. No reflective screen. Usable without backlight, even if it has one. If it can't be read for three hours straight at the beach with no eyestrain, then I don't want it.

    Anything else - backlight, color, wifi, bluetooth, whatever - is firmly in the "optional" category.

  24. Ian Ferguson

    "Reflected light in black"

    I do love the 'reflected black light' in that diagram - excellent SCIENCE as always from Wikipedia :)

    I will be happy to buy an ebook as soon as I can get one a) DRM free (or at least with the option of TXT/PDF), b) stylish (ie. NOT Kindle) and c) cheap.

    My guess is Apple will bring one out soon, and dominate the marketplace by selling ebooks through iTunes. They have the infrastructure, which is 99% of the problem, and why they won the MP3 wars; they'd be foolish not to at least try.

  25. Gordon 10 Silver badge

    Technology not hampering Ebooks - DRM & availability

    The biggest bar to more ereader use isnt the technology - althought faster refresh would be nice.

    Its availability of media. I own a Sony E-reader and an Iphone with the Stanza app. Guess which one I prefer? Stanza, I can get much more un-drm'd and a wider range of content libraries on Stanza than I can on the ereader. Battery life isnt an issue as I charge the iphone every day.

  26. Anonymous Coward
    Anonymous Coward


    Thanks, good explanation..will remain AC for now....

  27. Anonymous John
    Paris Hilton

    Re Cheap as chips

    A screen small enough to fit on a battery has to be cheaper than a six inch one. And the definition may be lower.

    Paris because she'd probably tell you that size doesn't matter too.

  28. Anonymous Coward
    Anonymous Coward

    pixel density

    Great article, but I'm pretty sure the assertion that there is one microsphere per pixel is incorrect - there are several, and not necessarily in alignment.

    on the subject of colour, separating the incoming light into RGB components reduces your maximum reflectivity to 33%. Any LCD based display cuts another 50% off because it needs polarisers.

    Oh, and RGB is necessary if the pixels are side-by-side, that makes it additive mixing. CMYK would be used if the pixels were stacked in the z-axis, like ink overlaid.

    The only colour technology to deliver more than ~10% reflectivity would be a tuneable photonic crystal - basically a bragg reflector, working on iridescence, but where the layer spacing can be controlled. This is a long way off, and has basic flaws like very narrow viewing angle, and an additional independent control of luminance (as opposed to pure chrominance) is required.

    So, Black and white is all you really get, its all you really need, the "Book 1.0" standard is still immensely popular.

  29. johnnytruant

    the thing about eInk

    Is that it was one of the first pieces of technology for a long time that genuinely made me go "wow" when I saw it in person. It's like HDTV or the touchscreen on an iPhone - unless you've got direct physical experience of one, you really don't have any idea just how impressive they are. Pictures on the internet really don't cut the mustard. Reading on a transmissive screen, especially a tiny phone screen, is like comparing piddly £1-a-pair earbuds to Kef floorstanding speakers.

    My iLiad isn't a replacement for a laptop/netbook, it's a different device. I read on it, and the refresh rate bothers me not a jot - it's pretty much as long as turning the page on a book, and after a while, you learn to hit the page turn bar just before the end of the last line - then the refresh appears seamless. I use it as a notebook, I handwrite notes and even draw sketches on it. Works very well in meetings, where tapping away on a laptop would be rude and intrusive. Nobody ever says - "hey, that thing's crap/pointless without colour on it", they all say "wow, that's hella cool, where did you get it".

    Colour, I don't miss at all. Sure, it'll be nice when it comes along - but the books I read don't have pictures in. How much of your library does? Some of them have diagrams, but they work just fine - I can zoom and pan if I need to (something my eyes can't do on their own!)

    Being able to set texts in your own choice of font/layout is great. Once you've started reading in Helvetica 10pt, you never want to go back. Being able to carry a fortnight's worth of reading - which on a holiday can run to several kilos of squashed tree, for me - in one book-sized device is a major plus. The iLiad even has a powered USB socket on the top, into which one can insert a little gooseneck led light - perfect for reading in the dark.

    Yes, eInk isn't a fully mature technology. But it's very good for what it's doing now, it's certainly not crippled by a lack of colour. That's a bit like saying radio is crippled by a lack of pictures. Most radio doesn't need pictures any more than most books need colours.

    @Paul4 - I love books. I have rooms full of books. I still buy hardbacks of books I love, and I want to keep them (then I format shift to ebooks to read 'em, usually). But I'm not so attached to my softbacks - and that's what eBooks replace. To compare to music - albums I really love, I buy on vinyl. Albums I just want to hear, I used to buy on CD, now I buy on MP3. My feeling is that e-reading will go the same way - you can already see the resurgence of the boxed hardback, or the illuminated editions of books at premium rates - while all the time the price (and paper/print quality) of softbacks plummet.

  30. Trygve


    Try Calibre. My Sony is chock-full of non-copyright stuff, it's all good.

    And to everyone bleating about reading on laptops/phones/PDAs whatever. Can you read 6-8 hours a day every day for five days without eyestrain (and on on a single battery charge)? I doubt it. Whereas I took my PRS505 on holiday and plowed through half-a-dozen books with no trouble at all.

    These e-ink devices are still too expensive and it's a faff obtaining and loading content. But apart from that they are the bee's knees, even in black & white.

  31. Andy Gates
    Paris Hilton


    Comics. That's why colour would be great.

    That and porn, obviously.

  32. Graham Bartlett

    @Si 1 and others

    Yes, the idea of colour is so it can show photos and stuff. Ultimately the aim is for e-ink tech to replace existing displays. The reason your mobile phone battery lasts 10 hours instead of 1000 hours is almost entirely down to the display, and battery technology is fairly stagnant, so any improvements in lifespan away from a charger can only come from reducing power consumption.

    At the moment, of course the display won't compete with an LCD. But the e-ink tech is in very early days, so it's not exactly surprising. It's like someone in the 1980s looking at an LCD calculator display and saying "Use that to make a TV screen? It'll never happen!" Unless you have inside info about how history's going to turn out over the next 20 years, it'd be a bit dumb to bet against it.

    FWIW, e-books *do* hurt my eyes. Contrast is laughably bad, trying to see dark-grey text on a light-grey background, and resolution is lousy enough that all text has a horrible attack of the jaggies. Plus the eye-killing refresh flash as well. Not good. Thing is though, e-books are kind of in the position that the first house-brick-size mobiles were - they're hopeless on many levels, and they're ludicrously expensive for what they do, but if you happen to want the one thing they do well (which in the case of e-books is allowing you to store a zillion books and read them any time) then you might still buy one if you've got money to burn. Eventually they'll get there. Like mobiles, there'll be a steady chain of improvements, until one day you look up and find they're a practical gadget.

    The problem of course is whether display technology will still be around in the same form in 20 years time. Wearable see-through displays for Augmented Reality (a glasses/monocle equivalent of the Bluetooth earpiece) are clearly the way things are going to go, and that may invalidate all assumptions about future computer monitors, TV screens and e-books.

  33. Alan 6


    A good colour E-Ink screen would be handy as a digital photoframe. It'll save running them on mains, you'd just need enough juice to change the image now & again...

  34. Matt Bucknall

    @h 6

    No, if it were possible, e-ink displays could be backlit. Because an e-ink display works by moving opaque black and white particles to the front or back of the display, you cannot shine light through it.

  35. Charles King

    Resolution is the key

    You missed the real problem with colour eInk - resolution.

    A colour eInk display requires 4 separate cells (RGBW*) for each pixel, and each cell needs to have at least 4bits of scaling to produce marginally acceptable colour. Now, current eInk displays on the market have 4bit displays at a res of 166dpi for a 6" screen (200dpi for 5", 150dpi or less for larger sizes). Divide that by half for the 4-cell pixels and you get 83ppi, about 30% less resolution than current LCDs and far too little for decent text at 12pt. The 166dpi of current eInk readers is 'good enough' to display small text when combined with greyscale aliasing, but going down to half the res would produce a pixellated mess that isn't going to sell.

    So, the big challenge is to increase the resolution of the screens, something which requires a major upgrade to manufacturing and quality control techniques that no-one's cracked yet. I'm sure we'll see low-res colour epaper screens used for point-of-sale and other sorts of displays, but it's a while still before someone will come out with a colour device that will be comfortable to read for long periods while a foot away from your nose.

    *As for the filters, they're RGB because the actual reflective surfaces are either white or black and the filters lie over them, so you need to use transmissive filters which shine red light on the white balls for a red dot, etc. Ink on paper works differently since the ink only reflects part of the spectrum, whereas eInk balls either reflect all of it or none. If they were able to create cells with different pigments then they'd be using CMYK, but that would need some very costly manufacturing. The W is a white, or clear cell that's needed to increase the contrast.

  36. Adam Foxton

    I have a solution

    or at least I think I do. One that also neatly circumvents Charles King (above)'s problem of resolution and Matt Bucknall's opacity problem.

    Rather than using black and white charged-balls with no backlight, what's to stop them using black and transparent? Actually, black and white balls would probably still work but you'd need a brighter backlight...

    The idea would be that you'd have the e-ink screen suspended over an OLED screen. Each OLED pixel would be the same size as the e-ink pixels- they're a lot smaller so it should be easy. OLEDs have been used in flexible displays as well so there's still no limit to how they can be applied.

    The e-ink would permanently show a greyscale version of the image, which would be coloured in by the OLEDs. This would still be low-power as OLEDs are low power and could be set up so only the image-covered portion of the screen was consuming any power at all- and with the refresh rate limitations of e-ink you're not talking about needing super-advanced display controllers.

    When power was turned off or the OLED reaches the end of its useful life you'd be left with a greyscale image- perfectly satisfactory for a large number of tasks. However, when you wanted the full experience you'd be able to turn on the OLED backimage- giving you glorious colour and the ability to use it in the dark without a torch.

    Such a device would be slim, use very little battery power and cost only a bit more than a normal ebook reader (depending on OLED costs...). Black/White-Fluorescent-material balls could make it even lower power as you could pulse the OLEDs rather than keeping them on all the time.

    If using black/clear balls you could always put a layer of paper (or another flat white layer) between the OLED and the e-ink so it goes white when OLED power is off. Or use clear and white so it's either white (i.e. virtual "paper") or see-through(i.e. coloured)/grey/black (the colour of a non-powered OLED display).

    Alternatively you could use PLEDs or some other type of really skinny light-emitting system as the backimage

    If such a device is now released, you heard it here first... and if you heard it here then built it and made money, please get in touch with some royalties or a job as I'm skint and unemployed...

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  38. Tom 7 Silver badge


    Why should I have to buy a whole new computer and all the crap that comes with it - why cant my phone, laptop, netbook... have a (bluetooth) Digital Ink screen so I can read with that. It would be light (weight wise) and do all the things an e-reader does - apart from making someone else rich selling me shit I've already got and probably run for days on a rechargeable AAA battery.

    I could have a nice black and white one for now, and colour as I see fit - except the people pushing this have a different agenda.

  39. Jason DePriest

    Time to upgrade

    "You'll be wanting BOOK version 9, then." [1]


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