Jun 042011

Diagonally-confusedThe problem

Screen size is usually advertised solely as the length of the diagonal. This is a useless measurement, it’s confusing to consumers, it makes it quite difficult to calculate the area, and it causes the industry to optimize to inappropriate metrics.

Let’s break that down…

How big is your screen? If it’s a desktop LCD, it might be a 22 inch screen. That, as we all know, means it’s 22 inch diagonal. We came to accept that the screen size is defined by its diagonal. That’s nice, except that’s not how geometry works. In some world where aspect ratios were uniform, measuring by diagonal might make sense. But that’s not the reality we live in. Form factors range from tiny mobile phones, to tablets, laptops, desktops and even huge wall displays, with very different aspect ratios. We have “wide” screens and “square”, non-widescreens, and yet we try to compare their size by using the wrong tool – the diagonal.

The solution

We propose moving to a more sensible measurement –surface area.  The area is probably what people care about – how much stuff you can actually fit on the screen. This allows you to meaningfully compare screens of different form factors. But why do we even limit ourselves to a single number to represent screen size? It’s a rectangle… and rectangles are defined by 2 numbers – height and width. Why not just use the exact measurements? Why not just advertise the screen as say a 15×11 inch screen? Consumers are capable of understanding two numbers. They are already used to seeing resolutions in this form. While we’re on the topic, it’s somewhat odd to use inches to measure technological assets in an era where only 2 countries still use this ancient outdated unit… by the metric system is a topic for another day. To summarize, the specification of a screen must include the following info:

  • Width and Height: such as 15×11 inches
  • Area: such as 165 square inches
  • Diagonal… because that’s what people are used to

Why this is important

  • Full disclosure of information – the diagonal alone does not give enough information to calculate area. To do so requires knowing the aspect ratio. It may not be clear what the aspect ratio is, or how to obtain that information. And even if the information is available, the math involved (simple as it may be) makes the result inaccessible to most people.
  • Consumer education – highlighting the wrong criteria causes consumer to make wrong decisions based on invalid priorities. It is important for customers to compare different offerings based on the criteria that are truly valuable to them – the area, rather than a meaningless diagonal.
  • Optimization to metrics – manufacturers know that most consumers equate the diagonal measurement with screen size. Therefore, in the eyes of a manufacturer, it is beneficial to optimize screens to have the longest diagonal with small area possible, reducing actual screen size and expenses. This results in the push we see in recent years towards wider and wider aspect ratios. The diagonal becomes larger, the actual area does not, and consumers are happy to get “a larger screen” but don’t realize they are being manipulated.

What can we do?

Diagonal measurement is an industry-wide issue. Many people don’t even realize that there is a problem. You can help:

  1. Understand the issue – knowing only the diagonal length is confusing and deprives the consumer of necessary knowledge, such as height\width or at least the area.
  2. When dealing with screen sizes, make informed decisions yourself. You can use an online calculator to translate between the given metrics and more meaningful ones.
  3. Communicate to other people using the area of a screen rather than the diagonal. Explain to them the issue and correct them when they compare products based on diagonal measurement.
  4. Demand from manufacturers to state the width, height, and area measurements of a screen in their advertising material, in addition to the traditional diagonal. You may contact most manufacturers easily online.
  5. Join the cause!