NWA-PCUG Newsletter Article, April 2010
Making Windows More Legible
Written by Gary Bentley, Editor,
Throughput, Southwest International Personal Computer Club, El Paso, TX
g.bentley (at) att.net (click to email author)

This article has been obtained from APCUG with the author’s permission for publication by APCUG member groups; all other uses require the permission of the author (see e-mail address above).

Have you noticed that each time you purchase a new computer with a higher resolution screen you find everything on the screen looks smaller than it did on the lower resolution monitor screen (if the diagonal size of your monitor was increased you might offset this phenomenon somewhat, but still be surprised that things looked about the same size in that case)?

This is because the Windows operating system assumes that the actual number of pixels per actual inch lighting up on your monitor screen is 96, i.e., 96 DPI (“dots” per physical inch) is assumed by the operating system.

Why would this assumption make things (icons, pictures, text, etc.) look smaller on a monitor that had higher native resolution (native resolution meaning the actual number of pixels lighting up per actual physical inch on your screen)?

Let us look at a real-world example. My Dell Latitude D620 has a 14 inch diagonal LCD screen with 1440 (horizontal) by 900 (vertical) pixels (native resolution, i.e., actual LCD pixels). How many DPI, i.e., pixels per inch is my screen? Well, recalling the Scarecrow’s recitation in the Wizard Of Oz when he received his “brain diploma” (or what he should have said, since he actually misstated the Pythagorean theorem---we can only assume that the Wizard did not want to damage Scarecrow’s self-esteem by correcting him), we know that the 14 inch diagonal on my screen is the hypotenuse of a right triangle, the sides of which are 1440 and 900 pixels. So we can take the square root of the sum of the squares of those two sides and that will give us the number of pixels along the 14 inch diagonal. The square root of 1440 squared plus 900 squared is, using Wolfram|Alpha (http://www.wolframalpha.com/examples/Math.html, use the basic arithmetic box there), 1698. Note that Wolfram uses standard means of entering mathematical operators. You might have to look those up and make adjustments, e.g., I asked for the square root by telling Wolfram to take the parenthetical operations to the 0.5 power since I knew how to enter the exponentiation operator (“^”), but not a square root sign (a radical sign).

So we have 1698 pixels along my 14 inch screen diagonal, or 1698 pixels/14 inches = 121 pixels per inch (121 DPI). How wide is one pixel? 1 inch/121 pixels = 0.008264 inch per pixel. Why would this make things smaller on my Windows desktop? Well, Windows assumes 96 pixels make an inch, so an inch on my screen is now 96 x 0.008264 or 0.79 inch. So everything on my Windows desktop is only 80% of the size it would be if there were actually 96 pixels per inch on my screen. I can verify that my calculations are correct by setting Microsoft Word to display an 8.5 x 11 inch standard document at 100% size. When I measure the width of that document on my screen I obtain 6 13/16 inches or 6.8125 inches. 6.8125/8.5 = 0.80, i.e., the 8.5 inch wide document is displayed at 80% of its actual size as we calculated would occur.

This means that text fonts are 80% of their intended size on my screen also. Fonts are defined in terms of points. A point is defined as 1/72 inch, i.e., 72 points per inch. Window assumes there are 96 pixels per inch, so a Windows logical point is 96/72 = 1.333 device independent pixels. A 10 point font should be around 10 x 1.333 pixels or 13 pixels vertical (leaving aside details of leading, etc.). That would be 13/96 = 0.13 inches high roughly on a 96 DPI monitor. On my 121 DPI monitor that 10 point font would only be 13/121 = 0.10 inch high approximately, again about 80% smaller.

A Microsoft study indicates about 55% of people reduce the resolution of their monitors (configure Windows screen resolution in Display Properties for a lower value), presumably to make the text and other items on their computer screen larger. For example, if I changed my laptop screen resolution to 800 x 600 there would be fewer Windows pixels to cover the same area, so the “pixels” would be larger, making everything constructed with those fat pixels larger too. Fat pixels make fuzzy or pixilated images, though they are larger images. This is rather like purchasing a $474 Canon EOS Rebel with 10 Megapixel resolution and then setting it to take 640 x 480 photos (when you have paid for a camera that can take 3648 x 2736 pixel photos roughly).

A better way to increase the size of text and other items on your screen is to use Windows DPI scaling. You can tell the operating system that you want an inch on your screen to be made up of more than 96 dots/pixels (if you don’t have a monitor with more than 96 actual dots per inch this would not work as well, since the operating system would have to “fake” the additional pixel density using mathematical algorithms). In Windows XP you can right click on the Desktop, select Properties, then Settings, then Advanced, then DPI setting. Choose more dots per inch, say 120 DPI. Go higher if needed. Evaluate the effect in normal use of your system.

In Windows Vista, Open Personalization by clicking the Start button, clicking Control Panel, clicking Appearance and Personalization, and then clicking Personalization. In the left pane, click Adjust font size (DPI). If you are prompted for an administrator password or confirmation, type the password or provide confirmation. In the DPI Scaling dialog box, increase the size of text and other items on the screen by clicking Larger scale (120 DPI)–make text more readable, and then click OK. You can use higher DPI settings to obtain still larger fonts and objects.

If we chose to scale up to 120 DPI on my laptop, then an inch would be 120 dots/pixels and a Windows inch on my screen would indeed be an inch, restoring the size of items on my screen to that of a typical 96 DPI monitor. I should note that Internet Explorer 7 and 8 both have a zoom feature which will enlarge text and other items on a web page. This is a separate issue in some respects.

How big would that 10 point font be if you used a 64.5 inch diagonal HDTV with 1920 x 1080 native resolution with PC VGA input for your computer monitor? Calculate screen DPI: 34 DPI (calculate the number of pixels in the 64.5 inch diagonal for 1920 x 1080 pixel right triangle as we did above; divide that number of pixels by 64.5 inches). Simply looking at the ratio, the HDTV pixels would be 96/34 or 2.82 times larger than a 96 DPI monitor. So, a 10 point font might be around 0.13 inch x 2.82 = 0.36 inches high---over a third of an inch. And if you scaled up your Windows DPI setting to 200 DPI, you might get that 10 point font up to 0.8 inches high (over three quarters of an inch high) on that 64.5 inch $4,000 dollar HDTV computer monitor.

I have barely scratched the surface on this topic, but I hope I have said enough to give you some ideas about making things more visible on your computer screen without throwing away the high resolution of your monitor.

Mr. Bentley studied electrical engineering at the University of Texas, began working in the electronics industry in 1978 with GTE Network Systems (Lenkurt), then software engineering with various startups in the 1980’s, designing and implementing, among other things, pre-Internet email communications systems multitasking on Intel platforms and MSDOS PC’s 1984 - 1986. Gary now provides Information Technology consulting services in the El Paso, Texas and Las Cruces, New Mexico areas. Gary has edited and contributed articles to the award-winning Southwest International Personal Computer Club monthly magazine, “Throughput”, since December, 2003.

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