The definition of screen is the number of points or Pixel S which a Graphics card can post. The definition is the product of the number of points according to the horizontal one by the number of points according to the vertical of posting.
To use a given definition, it is necessary that the Graphics card is able to post it and that the monitor can support it. The size of the screen and its not of drilling define the maximum definition which one can reach without loss of quality with regard to the image.
It is also possible to use two monitors with a central processing unit: that makes it possible for example to have a number of pixels in width twice larger, and thus to use for example a definition of: 2048×768 points.
For a printer or a scanner, the definition - to see numerical Resolution - indicates the number of points which can be digitized or printed.
Table of the definitions according to the size of the screen and its pitch
The vertical definition depends on the horizontal frequency of the monitor, expressed in Khz, which is the product of the frequency of screen by the vertical resolution (which is typically of 50Hz in PAL/SECAM, 60Hz in NTSC and on basic screens VGA or flagstones LCD, and of 70Hz, 72Hz or 75Hz on the screens with cooling raised to limit the effects of flutter). Generally, the vertical resolution obtained is only its theoretical maximum value, because certain lines are often removed (remain black) on the screens with analogical connection (even if the screen is a flagstone LCD or TFT) to make it possible the electron beam to vertically move at the time of the return of sweeping for the following screen on screens CRT.
In the same way the frequency of pixel (expressed in MHz) gives a maximum horizontal resolution. There too the horizontal resolution obtained is the theoretical maximum, because a certain number of pixels cannot be posted at the time of the return of sweeping.
On the screens TV, the sweeping of the screen is often done in interlaced mode, two shifted successive screens of a line and posting each one a line on two being necessary to sweep all the screen (this technique decreases the flutter, and benefits from the high Rémanence of the cathode tubes TV, this remanence being the equivalent of a memory of screen). New screens TV offer a double sweeping (100Hz in PAL/SECAM or 120Hz in NTSC) by using a memory of complete screen, that does not increase the resolution but reduced the flutter interlines, and makes it possible to transform the two half-screens of a signal interlaced into not interlaced complete screens covering all the screen (and not half of the lines) at the normal frequency of 50Hz or 60Hz.
However, it is not enough to increase the frequencies to obtain a better resolution. The screen comprises a mask indeed determining the number of luminophores reproducing the pixels. On an analogical cathode tube screen, the pixels can post only the average of the modulated signal of the beam during their exposure to sweeping. It is not possible to address the luminophores individually, because it is impossible to make correspond exactly the electronic beam with the fixed mask to avoid exposing a luminophore located 3 under-pixels before or after or 1 pixel to the top or in lower part. Moreover, the majority of the cathode screens have a single grid for the three colors, the beams only being shifted angularly so that the beam crossing the mask exposes the luminophore of the good component color. The under-pixels thus were often laid out in triangle and not aligned horizontally. Today screens CRT use beams aligned horizontally, and a mask with vertical slits making it possible to expose horizontally aligned rectangular under-pixels. That reduces the vertical flutter, and increases the clearness of the image, but that still does not make it possible to expose each luminophore precisely.
On flat panel displays (LCD, TFT, with plasma and other techniques with active or rétroéclairée matrix), there is no electron beam but a sweeping is in spite of very necessary to numerically address them by their address. However these screens often impose a nonadjustable frequency of single cooling, because the duration and the frequency of excitation of the luminophores is characteristic of their color, but also this frequency is imposed by the technology of transistors used to allow the decoding of the addresses of columns. When a flat panel display offers adjustable frequencies, it included makes a memory of screen for the entry signal, and transforms the signal entering via this temporary intermediate memory and reconstitutes itself of it its own sweeping starting from this memory. But contrary to the cathode screens, each luminophore is addressable very precisely in an individual way, which allows the use of techniques of improvement of posting like ClearType.
The higher the definition is, the more the screen is powerful, however the frequency of cooling of the screens is also important because it determines the quality of animations and the more faithful reproduction and more rapid of the movements (a determining factor for the players, because if the eye does not offer a raised resolution, it is on the other hand very sensitive for the detection of movements, which allows actions conditioned reflexes).
Another determining factor for the quality of the screens is the precision of the colors. That depends at the same time on the treatment of the signal (amplification, corrections colorimetric) but also of the nature of the luminophores, of which or luminous absorption emission spectra of the electronic beams, or frequencies of excitation for screens LCD or to plasma) is determining, just as the relative geometry of the luminophores (for example the step separating each under-pixel which must be weakest possible, so that the maximum of surface is source of light, and permanently does not remain black), and of also of the step of mask used (the weaker the step of mask interpixel is, the more it is difficult to maintain a surface luminous important at entire surface equivalent).
See the measuring units in data processing for more details.
The following table present of flagstones 4/3 (the width is 1,333… times larger than the height).
See too
Simple: Display resolution
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