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Computer Skills Course: Displays and Monitors

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Published on Apr 13, 2016

Free Computer Skills Course: Displays and Monitors. Learn about Size, Aspect Ratio, Resolution, Pixel Density, and Refresh Rate.

Transcript:

Let’s take a look at displays, such as computer monitors, televisions, and the screens on portable devices. The display is the primary way that a device communicates information with you, so it’s obviously super important. There are several key terms that we’ll cover, including: size, aspect ratio, resolution, pixel density, and refresh rate.

Let’s start with the simplest of the terms: size. Display sizes are generally defined in inches, such as a 20” computer monitor, or a 4” smart phone screen. This number, in inches, refers to a diagonal measurement from one corner of the display to the other.

Next let’s look at aspect ratio. Aspect ratio refers to the how wide the display is relative to its height, and is expressed using two numbers, which are written like this: 4:3, 16:9, and pronounced as “four by three” and “sixteen by nine”. The first of these numbers refers to width, and the second refers to height. So a 4:3 display is just slightly wider than it is tall. 4:3 happens to be the aspect ratio of the original television format, so when you see older TVs, those are 4:3, and older television programs and VHS movies are in 4:3 format. Many older computer monitors, and even some new ones, are also 4:3. Modern televisions are much wider than their 4:3 predecessors; they generally have an aspect ratio of 16:9. 16:9 is actually a very common aspect ratio today, it is found in TVs, computer displays, and even smartphone screens.

Our next term is resolution. Resolution, simply put, refers to how sharp and detailed a display looks. To really understand resolution, you first need to know that everything you see on a display is composed of pixels. Pixels are tiny individual dots of light that make up everything you see on a screen.. The resolution of a display is expressed as two numbers. The first is the number of horizontal pixels, and the second is the number of vertical pixels. Here are some examples of display resolutions:

Resolution: Monitors
First VGA monitor by IBM (1987): 640x480
15” LCD Monitor (1997): 1024x768
Modern Full HD Monitor: 1920x1080
Modern QWHD Monitor: 2560x1440
Modern 5K monitor: 5120x2880

Resolution: TVs
Early High Definition 720p TV (1998): 1280x720
Modern High Definition 1080p TV: 1920x1080
Modern High Definition 4K TV: 3840x2160

Logically, if you were to multiply the height by the width, you’d get the total number of pixels on the display. For example, a 1920x1080 display contains about 2 million total pixels. In general, the higher the resolution, the better, as the image will look sharper and you’ll be able to fit more content on the screen at a time.

The next term, pixel density, tells you how closely the pixels are crammed together; it’s an expression of the relationship between size and resolution. For example, a 27” desktop monitor with a resolution of 2560x1440 has a pixel density of about 109 pixels per inch (abbreviated as PPI), while a smart phone with a 5.1” screen and the same resolution of 2560x1440 has a pixel density of 534 pixels per inch. This figure refers to the number of pixels horizontally and vertically in one square inch, so you would square that number in order to find the total number of pixels in a square inch. In the case of the aforementioned smart phone, it would be 534x534 = 285,156. That’s a lot of pixels for one square inch. In fact, there comes a certain point, which is arguably much lower, around 300 pixels per inch, beyond which the human eye simply can’t tell the difference. Beyond that point, it may just be a waste of battery life to have such a high resolution display on a mobile device, unless you’re planning on strapping it to your face as a virtual reality headset, but that’s another topic.

Our final term is Refresh Rate. Refresh Rate is measured in Hertz, which is usually abbreviated as Hz. The word Hertz is actually a general term used in a variety of contexts, and by itself it just means “cycles per second.” It the context of displays, it refers to how many times per second a display can ‘refresh’ itself. By refresh, I mean update itself with a new image. In cinematic terms, you could think of this like the number of frames per second that a display can produce. The lowest refresh rate that you typically find on any monitor or TV is 60hz. That’s pretty fast, especially when you consider that a traditional theatrical movie is only 24 frames per second. That said, for some reason there has been a race among TV manufacturers to achieve the highest refresh rate possible, and it’s possible to find TVs now with refresh rates of 120hz and even 240hz. Personally, I think it’s kinda silly, and that 60hz is plenty for all intents and purposes, with the possible exception of hardcore PC gamers.

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