Display size
On 2D displays, such as computer monitors and TVs, the display size (or viewable image size or VIS) is the physical size of the area where pictures and videos are displayed. The size of a screen is usually described by the length of its diagonal, which is the distance between opposite corners, usually in inches. It is also sometimes called the physical image size to distinguish it from the "logical image size," which describes a screen's display resolution and is measured in pixels.
The TV image is composed of many lines of pixels. Ideally, the TV watcher sits far enough away from the screen that the individual lines merge into one solid image. The watcher may sit even farther away and still see a good picture, but it will be a smaller portion of their visual field. The resolution of the human eye (with 20/20 vision) is about one minute of arc. For full HDTV resolution, this one minute of arc implies that the TV watcher should sit 4 times the height of the screen away. So the ideal set size can be determined from the chart below by measuring the distance from where the watcher would sit to the screen in centimeters (or inches), dividing that by 4, and comparing with the screen heights below. Do not be surprised if the observer can see the pixels at this viewing distance as most normal people see far better than 6/6 ([20/20 vision]). If the user is replacing a standard definition TV with an HDTV this implies that the best visual experience will be with a set that is twice as tall as the standard definition set. As the average size LCD TV being sold is now 38", which is only about 15% taller than a 27" standard definition TV, this means that most consumers buy HDTV sets that are smaller than what they could utilize. Cost and budget also limit screen size.
Knowing the actual height and width of a screen is useful when deciding which one to purchase. Common dimensions are listed in the table below. If the display is not listed, then the following equations can be used. Note that D is the diagonal (in centimeters or inches), W is the width (in pixels), and H is the height (in pixels).
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