Being Picky About Pixels

As more learning content, textbooks, and assessments become digital, screen resolution will play a big role in the next-generation of education-ready devices.

Years ago, I came across an interesting ad from a PC monitor company.  I cannot remember the name of the monitor company, but I remember their prudent statement in the ad.

“It’s the computer you’re buying, but it’s the monitor you are looking at.”

That single ad has kept me picky about pixels to this day.  It is my hope that after you read this article, you will become pickier about pixels too.

A Peck of Pickled Pixels

For the uninitiated, we should start with the question: “what is a pixel?”  Well, if you are reading this piece, you are looking at millions of pixels right now.  Pixels are simply the smallest unit of light that we see on our computer screens.

Pixels are everywhere. Digital watches use pixels, your car displays use pixels, your smartphone/feature phone has pixels–even your printer has pixels.  And print is the real reason, why we all should be pickier about pixels.

We measure computer screen pixels horizontally (width) and vertically (height).  The most popular screen resolution for laptops display is 1366 pixels across and 768 pixels vertically.  A screen with 720 vertical lines of pixels is high definition. However,  a screen with 1080 vertical lines of pixels is considered true HD.  Most of us cannot tell the difference between 720p or 1080p…but it is great for marketing movies and HDTVs.

Pixels Matter, Density Matters Even More

For the past 20 years, we have improved the display resolution of computer screens by increasing the number of pixels that they can display.  More pixels provide sharper images, more workspace for multiple apps, and improved on-screen reading.

With the improvements in pixel resolution we have also increased the size of computer screens from 10 inches to over 100 inch high resolution displays.  Ironically, as the screen sizes have increased, the pixel density has declined.  It is really basic math, a high resolution screen on a smaller size monitor provides for more densely packed pixels.  So you can have two true HD displays and the smaller screen will look better than the larger screen because the density of the pixels.

High Density Displays and the Elusive Paperless Office

If you are like most people, the so-called “paperless office” has been nothing more than a very expensive myth.  We all spend a ransom on ink for our printers because it has been easier to read (especially long documents) on printed paper than a typical computer screen.

Why is that?

When we look at computer screens for long periods of time, our eyes begin to experience fatigue and strain.  The condition has become known as Computer Vision Syndrome (CVS). While there are healthy computing steps that can be made to make this less of an issue, modern devices with High Pixel Density (also called High Dots Per Inch (High DPI)) Displays are also helping. High DPI displays have greater than 96 DPI.

Say Hi to High DPI in Windows 8

In Steven Sinofsky’s Building Windows  Blog, he talked about Windows “Scaling to Different Screen Sizes” and resolutions. Steven addresses the biggest questions that I am often asked, “Will Windows 8 have resolutions better than iPad’s Retina Display?”  The simple answer is yes. I encourage you to read Steven’s full article for details. As you can see from the chart below, Windows 8 supports a wide variety of resolutions and pixel density.

Screen sizes and Pixels Per Inch for Windows 8

Long form Reading

Since Windows Vista, Microsoft has been enhancing support for High DPI displays. With Windows 8 you can feel confident that you will have a number of devices at different screen sizes that are great for readability, usability, and visual appeal.

More importantly, you can increase the DPI on Windows 7 and 8 devices to improve readability and usability, regardless of the screen resolution or size. Visit this Windows site to see how to improve readability on your current computer.

For academic and business environments, High DPI displays could end or at least reduce our dependence on paper for our daily activities.  When the resolution of the screen is equal or better than a sheet of paper, printing out emails, assignments, websites, and documents should become a thing of the past.

Today, many media appliances and smartphones are shipping with High DPI displays (e.g. Nokia Lumia 920 and HTC Windows Phone 8X.)  This is a good signal that the entire industry of consumer displays are becoming more High DPI aware and better suited for long form reading. Keep in mind, while High DPI is key, the materials that the display screens are made will also impact usability and readability.

Calculation of monitor PPI

Below is a Wikipedia formula for determining the pixel density of your computer. Keep in mind, anything equal to or greater than 200 DPI is great for reading regardless of the screen size and resolution.

Theoretically, PPI can be calculated from knowing the diagonal size of the screen in inches and the resolution in pixels (width and height). This can be done in two steps:

1. Calculate diagonal resolution in pixels using the Pythagorean theorem:

d_p = \sqrt{w_p^2 + h_p^2}

2. Calculate PPI:

PPI = \frac{d_p}{d_i}


  • d_p is diagonal resolution in pixels,
  • w_p is width resolution in pixels,
  • h_p is height resolution in pixels and
  • d_i is diagonal size in inches. (This is the number advertised as the size of the display.)

For example, for a 21.5 inch (54.61 cm) screen with a 1920×1080 resolution (in which w_p = 1920, h_p = 1080 and d_i = 21.5), we get 102.46 PPI; for a typical 10.1 inch netbook screen with a 1024×600 resolution (in which w_p = 1024, h_p = 600 and d_i = 10.1), we get 117.5 PPI.

Note that these calculations may not be very precise. Frequently, screens advertised as “X inch screen” can have their real physical dimensions of viewable area differ, for example:

  • Apple Inc.‘s Mid-2011 iMac is advertised as a “21.5 inch (viewable) […] display,”[7] but its actual viewable area is 545.22 mm or 21.465 inches.[8] The more precise figure increases the calculated PPI from 102.46 (using 21.5) to 102.63.
  • The HP LP2065 20 inch (50.8 cm) monitor has an actual viewable area of 20.1 inch (51 cm).[9]


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