TV and monitor display technology. What are the differences between static and dynamic contrast?

It is a fundamental distinction between the Static and Dynamic Contrast. Define the notion of contrast is very important for three main reasons:

-       First, because this concept refers to the technology inherent in each display and then it should indirectly to understand the fundamental characteristics

-       In addition, the contrast ratio can severely interfere (for better or for worse) on all the other parameters of a display

-       Finally everything protect us from the many possible hoaxes and specific "accalappiapolli" often served up by manufacturers.



It 'important to remember that

In a progressive scan display type LCD LCD CCFL or LED lighting lamps date from CCFL or LED diodes, is always active. It follows easily that a real representation of the "black" will never occur, since the scanned images simultaneously (or "progressive") must be constantly backlit, otherwise the individual pixels corresponding to the liquid crystal, would cease to be physically visible, on the contrary conventional monitors cathode ray (CRT) mark the images alternately horizontally and vertically in time of a second, and not simultaneously, enabling shutdown of the physical passage of light (or better of the light beams generated by the electrons) in correspondence of black or dark areas.

NB. Worth a side note the contrast displayed on a plasma which is a sort of cross between LCD and CRT, though is closer to the latter: in fact, similar to CRT monitors, the individual fields of pixels of a Plasma gas loaded, they can physically go out, revealing blacks almost prefects, were it not that the same charge of noble gases must be always active / on, how to act as a "micro-lamp", thus introducing an albeit negligible factor lighting , and in part by limiting the display of black.

The Contrast

Each construction technology of display has a contrast ratio of its own. But what is it? On any display, the representation of "black" should not be understood in the sense of "black", same goes for the "white": black in fact, as we have seen, is the monitor's ability to "turn off" in some so the lighting, when the latter pushed to the maximum is no more than the "white".

We all know that in reality (except in very rare cases) there are no movies that represent images totally black or totally white, so it is important to understand how the display it changes from completely white to completely black, that is what black is actually in the "contrast" (note) with the maximum light (or white): more precisely, the unit of measure of this intensity is expressed in candelas per square meter (cd/m2), or more commonly through representation X: 1 (Example: 1000:1 , 10,000:1, etc..).

The Static Contrast is the physical ability of the panel to display the black (or rather "go out as much as possible") in relation to its opposite condition ("light up as much as possible"). Each construction technology has a greater or lesser ability to perform this procedure. The contrast values Static, being its panel, are the ones who approach nearer to reality and are in fact incredibly low (usually around 600 candelas per square meter (600:1) when compared to those in the Dynamic Contrast, because this ...

The Dynamic Contrast instead it has nothing to do with the display and its construction techniques, referring instead to the complex systems backlight forced and artificial, generated by the internal electronics to the TV and the increase in intensity of the lamps CCFL or LED . But as should surprise us with special effects and show off amazing specifications at the shopping centers, companies almost always show this value which refers to conditions totally incompatible with the real yield of the panel, as impossible: you get to declare that a display can show a contrast ratio of several thousands of candelas per square meter. The paradox in all this is that such a "contrast" (and is also out of place to call it that) dramatically alters the viewing of images, and also increases the infamous "ghosting" of the LCD, which is a nightmare for any company from ' invention of quartz watches attached to the keg Dixan today.


And how do you figure out how much contrast has a TV?

In the laboratories of the manufacturers we use two methods, and it is at their discretion be as honest or less:

The method Full On / Full OF is the most insidious, since it consists in sending screen is completely white, and then a completely black, but, as we mentioned before, in actual practice this will never happen with any movie, so do not says practically nothing. If combined with the Dynamic Contrast, therefore, may give rise to a formulation of the specifications that I would not hesitate to define obscene.

The method ANSI instead, send a chessboard screen to 16 alternating black and white squares. In this way the light extends beyond the scope of white that belongs to her, and tends to take a bit 'in the black since, as we have seen, the yardstick for determining the contrast reveals many flaws of the display, as well as naturally reduce the perception of contrast itself. It 'a condition that is closer to normal viewing of movies. A serious company should adopt the system ANSI Contrast + Static.



Translated via software




Italian version of

Seguici su Facebook