Eyeing the Display: Illusion and Resolution...

VikramMadan — Tue, 03 Apr 2007 11:19:00 GMT

Half the human brain (the half not fixated on media celebrities) is directly or indirectly associated with vision. Evolution has apparently decided that what we see, matters. Just as our eyes are our primary windows to our world, the displays on our mobile-computing devices are the primary windows to our information. The bigger we open our eyes, the larger our displays, the more the information we can absorb. Eyes work best when we don’t strain them, displays (LCDs only – I’m ignoring CRTs here) when we run them at their native resolution. We can perceive a few extra details by squinting (i.e. running the LCD display at a higher, non-native resolution) but it doesn’t feel natural. Things get blurry, headaches ensue. No surprise then that it’s in our best interest to find the optimal tuning between eye and display. Eyes you can’t tweak. But displays you can. Thank goodness.

Which brings us to our first topic for today: clarity of text aka ClearType. ClearType technology has been around for a while. Having watched it develop from a very close range – while I worked on the Microsoft Reader product – I willingly profess a certain fondness for it and personally think it’s both under-rated and under-utilized. For best viewing results, UMPC users need to pay special attention to ClearType.

First, a primer. On LCD displays only, ClearType smoothens font edges to make text appear crisp and sharp. Unlike CRTs, where a single un-manipulatable dot represents each displayed pixel, pixels on LCD displays have separately addressable red-green-blue (RGB) component-color sub-pixels (3 per screen pixel). When a character is rendered on the CRT screen, the underlying pixels are either part of the character, or they are not, leading to non-linear edges that make the rendered text look jagged and rough, a miniature version of prehistoric computer graphics on prehistoric displays. On an LCD screen, the jaggies still exist – except ClearType makes them 'more subtle’ by manipulating the 3 RGB sub-pixels under each ‘jaggy’ pixel. Since different RGB combinations produce different colors/brightness, in effect ClearType is manipulating the colors/brightness of the pixels that comprise the font edge. Because human vision is both imperfect and non-linear, from a distance the eye-brain perceives these color/brightness variations as smooth lines and not as colored patterns. In other words, ClearType makes text look good by creating an Optical Illusion. (The illusion itself is effective because the color variations Cleartype creates are themselves based on a model of human vision). And to think you thought Windows was WYSIWYG (What You See Is What You Get)! J Well, it’s not. You’ve been tricked. Talk to your brain! J

There are two key points above that impact your UMPC (or Tablet or LCD...) ClearType experience. Since you probably weren’t paying attention, I’ll call them out explicitlyJ:

(1) ClearType manipulates the Red-Green-Blue sub-pixels directly. The order in which these sub-pixels occur is called striping. The default striping for most LCD displays is RGB (in other words, Red followed by Green followed by Blue). In both Vista and XP, ClearType assumes by default that it is dealing with RGB striping and happily tweaks the pixel components using this assumption. Unfortunately for some of us, the default striping on some (many? all?) 7" UMPC displays is BGR (Blue, Green, Red – inverse of RGB). When you run Vista (or turn on XP-ClearType) on these BGR machines, instead of crisp, clear text, you get fuzzy, multi-colored, rainbow-fringed text! To a sensitive eye like mine, this basically sucks. The good news is that ClearType can handle BGR striping just as well as RGB striping – but you have to tell it to do soJ. The bad news is that there is no inbuilt UI in either XP or Vista to tweak this settingL. But the really good news is that you can run the ClearType Tuner from the Microsoft Typography web site to fix thisJ. Run, don’t walk. (This tuner has recently been updated for Vista. Hooray!)

(2) ClearType tweaks colors based on a human-vision model. As our choice in fashion (or mates!) shows, everyone’s vision works differently. The ClearType human-vision model is not a one-size-fits-all solution. Your perception of ClearType will vary from the person next to you, however much you like that person. Nicely enough, the ClearType Tuner also lets you pick a setting that looks best to your eyes. Another reason to give the ClearType tuner a spin. Sprint, don’t run!

Once you have ClearType adjusted correctly for your display striping and for your eyes, you’ll be surprised at how delightful it is to read text on the 7” UMPC displays (or any other LCD display). Note that ClearType only works at the native display resolution. This is because ClearType is expecting to manipulate each pixel individually. When you run at a non-native display resolution, you’re trying to squeeze more displayed pixels onto each physical pixel, which creates one big, fuzzy, on-screen mess. Which brings us to our second topic for today: the 800x480 default native resolution on 7” UMPCs.

The 800x480 resolution has an official name: WVGA. But an official name doesn’t make this resolution any less funky and non-standard, at least from the Windows perspective. Given how long 4:3 display ratios have held sway, you can’t quite retroactively blame legacy-app programmers for not foreseeing a future teeming with 5:3, 16:9 or other nifty vertical-horizontal combinations. (You can and should, however, hound programmers of new apps that continue to make the same ol’ mistaken assumptions). Due to this lack of futurist foresight, the poor UMPC user will occasionally encounter an errant app that chokes on the screen resolution, refuses to install, shows UI that runs off the screen, and/or exhibits other heartburn-inducing behavior. Thankfully, though, these issues are mostly in a minority. (The majority of Windows apps do work well on the UMPC today). And over time, the native display resolution is expected to move up a notch, which will hopefully make today’s resolution-related issues yesterday’s footnote.

For most of us though, the promise of a better future doesn’t quite relieve the pain of the moment. If you’re running 800x480 on your 7” UMPC, you’ve likely already experienced the first-hand joy of having ‘certain’ windows dialogs run off the bottom of your UMPC screen, making it impossible to get to the dialog buttons. One work-around is to briefly switch to a higher, non-native resolution (painful). Another work-around is to anchor your Windows taskbar to the side instead of the bottom, giving you more vertical working space (which fixes the issue for many - but not all – dialogs).

A third option, one premiering here for your pleasure and consumption, is to download the attached ‘wholly-unsupported' 'pseudo-power-toy’ UMPCScrollbar utility and run it on your Vista UMPC. This utility runs in the background (no visible/configuration UI) and pops up an on-screen scrollbar whenever it detects a non-resizable dialog taller than the available vertical working screen estate. The scrollbar then allows you to nudge the dialog up and down, so you can access the dialog buttons that would otherwise be inaccessible. See the 'readme.txt' in the zip file for more information.

[Note: The UMPCScrollbar utility is compiled against the Windows Vista SDK and will not run on XP. It was cobbled together as a means to an end and is neither aesthetically pleasing nor perfectly engineered. Plus I couldnt bribe anyone to test it so it would help if you kept your expectations appropriately low...:)]

Vikram Madan's Blog: Fun With Windows : Cleartype

Eyeing the Display: Illusion and Resolution...