LCD Density Explained

Discussion in 'Android Tablet Usage, Tips & Tricks' started by OffWorld, Feb 27, 2011.

  1. OffWorld

    OffWorld Junior Member

    Oct 5, 2010
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    Minnesota, USA
    Tablet / Device:
    Haipad M701-R, Augen Gentouch 78 (returned it)
    If there is one great reason to root your Android device it is to change the LCD Density setting. If you're new to Android you may not know what LCD Density means. Well, in a nutshell it is similar to changing the screen resolution on your desktop computer - but it isn't exactly the same.

    At first the setting numbers seem counter-intuitive. On your desktop computer, as you increase the screen resolution numbers text, icons, and applications all start to look smaller. However, on Android when you increase the density setting everything looks bigger. Wait, what's going on here?!

    First of all you need to understand that the Android User Interface uses something called a "display independent pixel" or a "dip" (yes, it's confusing because the density settings are in "dots per inch" or "dpi" which are considered the same as "ppi" or "pixels per inch" as well).

    The default LCD Density setting on Android is 160 dpi. As far as the operating system is concerned 1 dip @ 160 dpi = 1 screen pixel. It doesn't mean that's actually true, but you've gotta start somewhere. In my opinion it would have been a lot nicer if they'd chosen 100 dpi because then it would be an easy percentage thing, but they didn't so we're stuck with this formula:

    dip * (dpi/160) = scale

    So, let's say I change my tablet's screen density to 120 dpi. I've just scaled down my User Interface elements (icons, dock, widgets, etc.) to 75%. Everything looks smaller! If I change the density to 240 dpi I'm scaling everything up 1.5 times. Everything looks bigger!

    If you do any kind of web design targeting mobile devices this can initially be frustrating when you have a phone with a QVGA (240x320) screen and it insists the portrait width is 320 pixels wide. Well, Android devices with QVGA screens would normally have a density setting of 120 dpi to be useable so :

    320 dip * .75 = 240 screen pixels​

    On the other end of the spectrum you have high-density screens that pack a lot more pixels per inch. It's not an Android device, but you may have heard of the iPhone 4 "retina" display? It packs 326 dpi density. The screen's resolution is 960x640, but at that density everything intended for the iPhone 3GS screen (which is 480x320 @ 163 dpi) will be scaled up x 2. To take advantage of this and not serve up blurry, blown-up images an app or web site can substitute images created at twice the normal resolution so they look crisp and clean.

    Why bring up the iPhone "retina" display? Well, Android 2.2 "Froyo" came out with support for what Google calls "xhdpi" (eXtra High DPI) of 320 dpi and higher and Android 2.3 "Gingerbread" included support for "xlarge" (eXtra Large) displays 7" and up. Additionally there are some screen manufacturers working on even higher densities than "retina" - in 2008 Casio made a 2" screen at almost 550 dpi (not sure it made it's way into any devices) and last year announced a join-venture creating 4.8" displays at 458 dpi (that's full HD resolution!) - so eventually the high-resolution experience WILL also come to Android.

    So now you know!

    (btw, as much as Apple likes to pretend they were the first to bring a "print quality" display to a mobile device - 300 dpi is the minimum resolution considered "print quality" by the way - Toshiba beat them to the punch back in 2007! A 3" WVGA screen @ 313 dpi on a Windows Mobile 6 device).
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  2. LongBo

    LongBo Junior Member

    May 24, 2012
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    Thank you very much, your "explained" resolved problems which bother me a few days.

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