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Color Reproduction

The manufacturers usually utter one number when talking about the reproduction of colors on the screen of an LCD monitor. The number is either 16.2 or 16.7 millions of colors. However, there’s a trap here, too. Many matrices nowadays – and almost all inexpensive ones – cannot reproduce more than 262 thousands of colors, as represented by 18 bits or 6 bits per each of the three basic colors.

The image on an 18-bit matrix looks depressingly bad without any additional measures. Such a matrix is in fact only suitable for office work and maybe for games. That’s why the manufacturers realize the so-called Frame Rate Control (FRC), a method of emulation of the missing colors when the color of a pixel is changed slightly with every frame. For example, the monitor has to output the color RGB:{154;154;154}, and the matrix doesn’t physically support it, but it supports the two neighboring colors, i.e. RGB{152;152;152} and RGB{156;156;156}. If we were outputting these two colors alternately with the frequency of the refresh rate, the similarity of these colors and the inertia of the human eye (which doesn’t perceive flickering at a frequency of 60 hertz) as well as of the matrix itself (which is “smoothing” the moment when the colors are being switched) would give us what our eyes would perceive as some in-between color, i.e. the required RGB:{154;154;154}.

Of course, this is still an emulation, which cannot match the true “true color” reproduction, so such monitors are often specified to output 16.2 millions of colors – if you see this number in the specs, know that you are dealing with an 18-bit matrix. Unfortunately, the text “16.7 millions of colors” doesn’t mean anything – many manufacturers write this in the specs of their 18-bit matrices, too.

More complex FRC mechanisms are also used in practice, accompanying the more traditional dithering (when the necessary color is formed by several neighboring pixels of slightly different colors), i.e. changing not just the color of a single pixel each frame, but of a group of four pixels, for example. This allows for a more precise reproduction of colors the matrix doesn’t support, but the hitch remains the same – such matrices can hardly be considered “full-color” ones.

So, the quality of color reproduction of such matrices is largely determined by the quality of the FRC mechanism. There are two common problems: first, there appear transverse stripes in smooth color gradients. Sometimes it looks as if there are no FRC at all. This problem, however, mostly belongs to the first generation of “fast” matrices, although some stripiness can sometimes be seen in a modern model. The second problem is that the FRC algorithms may fail on some specific pictures (for example, a one-pixel grid, especially if it is combined with a smooth gradient), resulting in flicker – this flicker may be so strong as to make it impossible to work with the monitor. The latter effect can only be seen in the most inexpensive models, though.

We should also remember that the quality of FRC (and the side effects thereof) may depend on the brightness and contrast settings of the monitor (if brightness is regulated by the matrix, not by the backlight lamps) – in this case, the image may be flickering at certain settings only. Overall, flickering usually occurs with rather specific images, not preventing you from working comfortably with the monitor.

 
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