The (long overdue) need for another spec: Pixel size

This guest article was submitted by Robert A. Anson.


Question 1: Which screen has larger text and pixels, the one measuring 14.1-inches diagonally with a resolution of 1024 x 768, or the one measuring 18.1-inches diagonally with a resolution of 1280 x 1024?

If you don’t know the answer, don’t feel bad. The point of this article is that you can’t tell from the information (specs) you are given. The only way to know is to look at the two screens, measure the same item on both, and compare the sizes.

If you're dying to know the answer to the opening question, they both have pixel sizes (the distance from the center of one pixel to the center of an adjacent pixel, including the space between them) of 0.281 mm, so the items (text, the Calculator window, an icon, etc.) are the same size on both screens.

Question 2 (based on a true story): There are three Apple Mac laptops you are considering for purchase. The "papa bear" (MacBook Pro with 17-inch screen), the "mama bear" (MacBook Pro with 15.4-inch screen), and the "baby bear" (MacBook with 13.3-inch screen). You aren’t a teenager anymore, so you want the laptop that has the largest text (by virtue of having the largest pixels).

Quick, which one has the largest text? You take an educated guess and say the 17-inch laptop because it has the largest screen. Wrong! You think that your logic must be backwards. Next you say the 13.3-inch one because it has the smallest screen. Wrong again! The 15.4-inch laptop has the largest text (and pixels).

How do I know this? I was in the Apple store and measured the same item on all three laptops. All three screens displayed text that was about the same size, but the 15.4-inch one had the widest items of the three I measured. Yes, the people in the store who observed me thought I was "a little strange."

Question 3 (based on a true story): You are shopping for a new desktop computer and like the Hewlett-Packard All-in-One TouchSmarts. They have two models: a 22-inch one with a resolution of 1680 x 1050 and a 25.5-inch one with a resolution of 1920 x 1200. You like the 22-inch TouchSmart very much but are wondering if the 25.5-inch model might be better for you because the text is larger. You do not want the text any smaller than that on the 22-inch TouchSmart. You go to three stores to see the larger screen but none have it on display; only the smaller one is available for you to evaluate. So you buy the 22-inch TouchSmart, never knowing if you would have been happier with the larger model. Did you buy the best one for you?

Question 4 (based on a true story): You are considering buying a UMPC. The three you like are available only from Dynamism, who imports them. You do not have the option of going to a dealer and visually checking them out. The Viliv S5 has a 4.8-inch screen with a resolution of 1024 x 600, the Asus R50A has a 5.6-inch screen with a resolution of 1024 x 600, and the Viliv X70 EX has a 7-inch screen with a resolution of 1024 x 600. You are no math genius but are aware that they all have the same resolution; therefore the one with the smallest screen has the smallest text (and pixels) and the one with the largest screen has the largest text (and pixels). But is the text on the Viliv S5 too small to be able to comfortably read? Which one should you buy?

Question 5 (based on a true story): You know that a 7-inch diagonal screen with a resolution of 1024 x 600 is readable because you had a Samsung Q1 Ultra UMPC with these specs and you were happy with it. But this new NEC VersaPro UltraLite VS netbook looks very interesting. It has a 10.6-inch diagonal screen with a resolution of 1280 x 768. Gee, the screen is 3.6 inches larger; that should make the text more readable. But the resolution is higher, and that works against readability. So, are the UltraLite’s pixels larger, the same size, or smaller than those on the 7-inch, 1024 x 600 screen that is your reference point for visual comfort?

Five questions, one solution: I propose that computer and monitor manufacturers include the size of the pixels as one of the specifications they list. For example:

Type: Laptop
Screen size (diagonal): 13.3-inches
Resolution: 1024 x 768
Pixel size: 0.264 mm

Pixel size, combined with a chart you make after evaluating various computer types, screen sizes, and resolutions, will allow you to determine whether a computer or monitor is right for you (i.e., you are able to comfortably see the text on the screen) without having to personally evaluate the screen.

For example, you might need a pixel size of 0.150 mm for a 7-inch, 1024 x 600 handheld UMPC, a pixel size of 0.281 mm for a 14.1-inch, 1024 x 768 laptop, and a pixel size of 0.294 mm for a 23-inch, 1600 x 1200 desktop computer. Note: If you place your desktop monitor right behind your keyboard, the pixel size may be the same or only slightly larger than that required for a laptop. If you position the monitor far from the keyboard (so your cat can sleep between them), a larger pixel size would be required.

If this system were in place, the answer to Question 2 (concerning the three Mac laptops) would involve reading the pixel sizes listed on the information cards next to each of the models; a no-brainer.

In Question 3 (concerning the two TouchSmarts), you have two screens, each a different size and resolution. Not only can’t you calculate the pixel size in your head, but you also can’t even calculate it on paper because they are wide screens, not those with a 3:4 aspect ratio subject to the theorem "the square of the hypotenuse of a right triangle is equal to the sum of the squares of the two other sides" (Scarecrow in The Wizard of Oz).

The mathematical solution is: screen width (in mm) = 4/5 screen diagonal (hypotenuse in mm). Pixel size (in mm) = screen width (in mm) / number of pixels across. Unfortunately, this calculation doesn’t work for the newer wide screens. The only way to know which pixels are larger is to have the manufacturer tell us. If I were presented with the pixel size for each of the TouchSmarts, I would have known which model to buy without having to see the larger screen in the warehouse; problem solved.

For Question 4 (concerning the three UMPCs that must be mail-ordered), all I would need to do is go to a store selling a variety of computers and check out the pixel sizes of the three UMPCs with those screens on display that have the same pixel sizes. I would then know which would be acceptable. The Viliv S5 with the 4.8-inch screen has text (pixels) much too small for my tired old eyes, the Asus R50A with the 5.6-inch screen would be questionable, but the Viliv X70 with the 7-inch screen would allow me to read with comfort; again, problem solved.

Question 5 was a trick question to introduce the concept of distance. The Samsung Q1U is a small handheld computer (pixel size is about 0.150 mm) that is generally positioned about 10-inches from your eyes. The NEC netbook sits on a table and the screen is about 18-inches from your eyes. The greater distance requires larger pixels to give you the same visual comfort.

Thus, you cannot fairly com pare pixel sizes of two screens that are placed at different distances from your eyes. Instead, you must compare the pixel size of a handheld computer with that of another handheld computer, the pixel size of a laptop/netbook with that of another laptop/netbook, and the pixel size of a desktop computer and monitor with that of another desktop computer. Why? Because the viewing distance is different for each of them. The closer the screen, the smaller the pixel size can be for you to have visual comfort. Even though the Samsung had a pixel size about half the size I prefer for a desktop computer and monitor (0.280 to 0.300 mm), I was happy with the size of the text because the screen was much closer to my eyes.

Providing customers with the pixel size for each screen would be a great help to those shopping for computers and monitors, especially via mail order. The pixel size needs to be added to the published specifications. What I find truly amazing is that we have gone this long without having access to this valuable information. Yes, a few manufacturers do provide the pixel size (they are industry leaders and are to be commended for supporting their customers), but they are also the exception to the norm.

OK, now that I’ve got your juices flowing, write ten friends, who will write ten friends, who will write ten friends. They will each write their Congresspersons to get them to make it a federal law to list the pixel size in the specifications for each computer or monitor. Manufacturers who fail to comply will pay heavy fines (to help reduce the national debt).

Now onto the next big problem: Wouldn’t handling CDs and DVDs be so much easier if you could put your thumb through the hole? Couldn't it have been made a little larger? Who is the idiot who determined the size? There should be a law.

Bob Anson, a retired pediatric dentist, is very enthusiastic (committed? passionate? obsessed? neurotic? psychotic?) about making/updating his databases and wants access to them at all times, hence his interest in mobile computing. His interest in pixel size results from being 62 years old and wearing trifocals.

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Pocketables is a US-based online tech magazine that brings news, insights, opinions, and comprehensive reviews on various mobile computing devices, portable technology, and related topics to a global audience. We focus on devices that fit into pockets of all sizes, from jeans and jackets to backpacks and purses. The gadget experts that comprise our staff produce high quality articles and original features colored with real-life use of products over weeks and months, not first-impression opinions formed within hours or days.

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