Display size

The screen size is a measure of the size of a screen. It refers to the distance between two diagonally opposite corners.

The indication of the screen size is only limited functional. The advantage of a single measured value relative to the common specifying the width and height can only be used if all devices of a class have the same aspect ratio as it has long been common in televisions. Compared with the indication of the display surface offers the diagonal of the advantage that they can be determined by a single measurement and without invoice.

In advertising, the screen size is often expressed in particular in computer monitors and liquid crystal displays in inches. See also dpi.

• 3.1 side lengths and area
• 3.2 pixels
• 3.3 values
• 3.4 Comparison with paper

Use according to technology

In tube monitors ( CRT ) an indication of screen sizes is usually in two parts as a physical and visible screen diagonal, since for technical reasons, a portion of the tube is always covered. If only one value is specified, usually is meant the physical diagonal.

As was the decisive factor in the size specification of CRT monitors not viewable screen size, but the total size of ( mostly invisible) tube, the comparison value to flat screens usually be reduced by about two inches. A 19- inch CRT monitor that is equivalent to about a 17-inch LCD monitor.

Use according to device class

TV

Conventional televisions are predominantly in the range of 30 cm to 127 cm, with the largest classic tube equipment only reach about 85 cm visible screen size. The information is also used on projection screens, which have higher values. The classic aspect ratio was 4:3, but the current standard are devices with 16:9.

Computer Monitors

Most computer monitors have a screen size 48-71 centimeters ( 19 in to 28 in ), with the demand for larger devices continues to increase. Portable ( in 7 to 15 in ) and old (14 in to 17 in ) models are sometimes smaller, while larger units are used for professional, graphics-oriented applications ( DTP, CAD). Traditionally, the TV aspect ratio of 4:3 was usual, but in addition to the more square 5:4 are wider formats such as 16:9, 16:10, 15:10 (3:2) and more frequently, being more similar to the natural field of vision of man.

Small Appliances

There are also devices with screens less than 30 cm (12 in), such as mobile phones, PDAs, hi-fi equipment, etc., from energy, space or price reasons do not have larger displays or need.

Geometry

Side lengths and area

Is the aspect ratio ( a: b, eg 4:3 or 16:9 ) is known, can be according to the Pythagorean theorem with the diagonal (d ) calculate the side lengths (w, h), and the image area (A):

For example, has a 4:3 aspect ratio, with a 50 cm diagonal horizontal side of 40 cm (= 4/5 x 50 cm) and a vertical side of 30 cm ( = 3/ 5 x 50 cm), thus a total area of ​​12 dm ² ( = 12/25 cm ² · 2500 = 40 cm × 30 cm).

Pixel

The screen size of a point (P) can be determined in accordance with a known resolution (W = x, H = y):

The said screen with 50 cm diagonal would therefore at a resolution of 1280 px × 960 px ( 1.23 Mpx = ) square pixels with a theoretical edge length of 5/16 millimeters or 312.5 microns, which corresponds to 81.3 px / in (dpi).

Is the diagonal given, we obtain the image resolution (R ), ie the number of points per unit length (eg, dots per inch, dpi ) through an inverse operation:

For two devices having different aspect ratio ( a1: b1 and a2, b2 ), the diagonals have different (d1 and d2 ) in order to display an image with the same height (h) or width (w):

Values

Compared with paper

An A4 paper side ( 297 mm × 210 mm) has a diagonal of 364 mm ( 14.3 in) with an aspect ratio of √ 2 ≈ 1.414, ie between 4:3 and 16:10. An A3 page is double (420 mm × 297 mm), A5 half as large (210 mm × 148 mm). The U.S. letter format is similar in size to A4: 11 in x 8.5 in = 279 mm × 216 mm, diagonal 13.9 in = 353 mm.