back to article E Ink, Epson to build 'retina' display for e-book readers

E Ink and Epson are to jointly develop a electronic paper panel with a "retina display" pixel density... almost. Apple calls the iPhone 4 screen a "retina display" because its 326 pixels per inch (ppi) density is "so high that the human eye is unable to distinguish individual pixels". Actually, look hard enough and you can …


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  1. You're all dinosaurs

    It's all about angular resolution

    A true 'retina' display should match the typical angular resolution of the human eye at a given viewing distance. That's the specification behind NHK's Super Hi-Vision system, I'm not sure what resolution Apple's Retina display produces, but 300ppi should be similar to the 300dpi used in magazine printing, and that's a pretty good goal for any eReader at this stage of the technology.

    1. jubtastic1


      300dpi is a common resolution for digital source images used for quality print, the screens of dots that are actually printed are usually at 200dpi, the increased dpi of the image is to reduce moiré effects.

      The text, which is what you should be comparing an e-paper screen to, is usually rendered at 1200-2400dpi.

      Here's some closeups for comparison:

      Bear in mind that the resolution of the 'magazine' printing plate is usually well in excess of what most printing presses and papers can accurately reproduce.

    2. BristolBachelor Gold badge

      angular resolution

      There is a good article here:

      It says that the angular resolution of the eye for a line pair is 0.59 arc-minute.

      So if you have a display with 300ppi made up from 3 sub-pixels next to each other (R,G,B), and 2 green pixels next to each other, then you will see them as a single green block if you are further away than ~49cm. (unless my trig is failing me quicker than my eyesight, which is likely!)

      As a quick test with the diagonal white boxes in the "Android App of the week" advert on the right, I had to be 2m from my monitor before the diagonal lines became straight instead of stair-cases, which is the right distance for 72ppi.

      If you are closer than that, then you will see the two green pixels as two green pixels with a black pixel between them. Of course your brain will see all the pixels on the screen like that and may try to ignore it, but I guess that may cause eye-strain or reduced quality.

  2. Mage Silver badge
    Thumb Up

    Good enough

    300dpi is fine. Laser printers historically only printed a dot or not. Even with only 4 levels of grey you can make 300dpi look as good as 720dpi

    Also most people don't have the sharp enough vision at normal reading distance to see much more than 200dpi if the image is anti-aliased with a few grey levels.

    My LCD is about 133dpi and almost no-one has ever noticed the pixels.

    I look forward to getting an eReader with 9.7" screen and 300dpi. Great for A4 PDFs.

    PDFs reformat badly, so a 9.7" 300dpi will be very nice for reading and documents

    It allows a nice wide margin around "paperback" format text rather than text up to edge of screen.

    1. Anonymous Coward
      Anonymous Coward

      Kindle's screen is good enough

      You can't see the pixels. Whenever I've asked someone to guess what the resolution is they've overestimated wildly.

      1. ThomH


        Same thing here; I think part of it is that there's no gaps between the pixels, and they've selected fonts that are relatively aggressively fitted to pixel boundaries so there's limited need for anti-aliasing anyway. makes the point quite well, especially when you get to the 400x versus 375x zooms.

  3. PurplePerson

    Much better than colour

    Seriously, now we're starting to get somewhere. The addition of colour to E-Ink displays will be nice, but a massive increase in resolution is absolutely critical (for me at least). When I can get a reader that can comfortably render a full page PDF (technical books etc.) then I'm in, maybe in an 8" screen size (10" seems a little large).

    1. johnnytruant
      Paris Hilton

      A4 readers

      do you mean a Kindle DX, Boox M90 or similar?

      I have an 8.1" IRex iLiad and, even with more DPI to play with, an A4 PDF wouldn't be readable at that size. You really do need those extra few inches.

      Paris, because she really needs the extra few inches too.

    2. Alfred

      And what size, pray, is a "full page pdf"?

      You can make a pdf page an inch square or really really big.

      1. This post has been deleted by its author

  4. Cunningly Linguistic

    A pedantic "surely"

    Surely "jointly develop a electronic paper panel" should be "jointly develop an electronic paper panel"?

  5. L.B

    A little off topic...

    I looked at buying an e-reader a few months back and was put off by the price.

    Not so much the readers, but the e-books. I looked up a few books that I may be interested in and found that outside of the current Top-20 lists, the e-books cost more than the paperbacks!

    Sometimes they are as much as buying the hardback book, and that includes free P&P by real mail.

    So for the time being I'm sticking with paper: it does not need re-charging, they are very durable and don't break when dropped. They don't like water, but then again most electronics would suffer more. They can be given to friends and relatives and finally to the charity shops if you are done with it.

    I already have the 100 classics on my DSi, so I will wait a while longer plus the DSi also does games for when the trains are running slow than usual.

  6. Anonymous Coward
    Anonymous Coward

    A4 ?

    Most training books & manuals I've seen could be scaled to A5 with no loss of readability.

  7. tanj666
    Thumb Up

    Work or Play?

    I have both a Kindle 6" reader and a Sony 5" reader. Love both to bits. I use them for leisure (Play). I've tried putting pdfs onto them for work but they simply don't work well enough. I've converted some pdfs to kindle format and thats mostly ok, unless the text has columns in the layout. Close, but no cigar.

    As pdfs are more for technical reference (work) I'm thinking a bigger pdf capable reader will be the thing to go for. Colour isn't that important to me, readability is.

    I think this sort of high def image will be pretty good when it comes out, I might even save some pennies up to buy one.

  8. Anonymous Coward
    Thumb Down


    They'll give the reader away for free... and charge £1 per hour for the ink.

  9. Graham Bartlett

    Great, we've got resolution - now contrast, lack of flicker?

    Having played with my sister's Kindle that bro-in-law bought her for Xmas, I can confidently state that I wouldn't use one unless every other form of written material (including Post-It notes) in the entire world had somehow ceased to exist.

    Slightly-jaggy text isn't a problem. I grew up with an Amiga connected to a TV screen and then progressed via pre-VGA PCs, so I don't mind seeing pixels.

    But I'd like what I'm reading to be recognisably similar to black and white. The light-grey and slightly-darker-grey thing is just crap and kills your eyes. I remember the monochrome LCD monitors on late-80s early laptops, and even they had better contrast than a Kindle. I managed a few pages on the Kindle and then had to quit with eyestrain.

    And my eyestrain wasn't helped by the flick-flick-flick every time you turn a page. Since I'm a speed-reader and the Kindle is formatted like a single page of a largish-print paperback, turning a page happens about every 20s. It then takes at least 5s for my eyes to stop screaming at me after the flick-flick-flick before I can carry on reading.

    1. Ignazio

      Flicker? what flicker?

      I have a Kindle 3 and I haven't seen it flicker ever - unless you count changing pages. Grey and less grey? Not the case with this one, for sure. Very crisp black and white. Friend of mine was impressed by being able to read it on the plane. Two seats away.

  10. Graham Bartlett


    I quote: "flick-flick-flick every time you turn a page"...

    Glad to hear they've got better contrast now. IMO what they were selling back at Xmas was nowhere near good enough. Kept my sister happy, but then they're a gadget-happy couple anyway.

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