![]() This can correct errors where Cb and Cr are both too high or too low by the same amount. Broadly speaking, the Color control raises and lowers the level of the Cb and Cr channels relative to the Y channel. The solution the original video engineers created was to put Color and Tint controls on the display to allow users to correct for mismatches in overall amplitude of the three channels. Age of the various pieces of equipment, heat, minor variations in components and so forth can all cause the various signals to vary in amplitude, and not necessarily the same amount for each channel. The problem is that in the process described above, many things can happen to degrade or change the Y, Cb, and Cr signals. But broadcast analog TV has always been in composite form. It’s also possible to feed the display a separated “component” signal (using three separate wires), or a partially separated YC (often called “S-Video”) signal, where the Y signal is on one wire and the Cb and Cr are carried in multiplexed form on the other wire. This recovers the Y, Cb, and Cr channels, or a close approximation, and the three channels are fed into a decoder that converts them back into R, G, and B, which is then fed to the display driver circuitry. The Cb and Cr signals are sent through a lowpass filter to compress their bandwidth, all three signals are multiplexed together into a single channel called “composite” video, and the signal is transmitted over the air.Īt the television, the composite video signal is demultiplexed (which is a whole complicated topic in itself). So at the television studio, the cameras are sensitive to R, G, and B, but those three signals are fed into a converter that outputs Y, Cb, and Cr. In essence our visual system has more brightness resolution than color resolution. This works out reasonably well because the perception of sharpness in the human visual system is primarily related to the sharpness of the luminance channel. So the color channels needed to be much lower quality. However, the extra signal space couldn’t carry nearly as much picture resolution as the main signal. The second part of the solution was figuring out that there was a small bit of bandwidth left over in the transmission signal that the original video engineers didn’t consider, and that would be ignored by the old televisions. The old televisions could just display the brightness (Y) channel, which makes a perfectly viewable black-and-white picture by itself. Then G could be recovered because Y is a simple weighted combination of R, G, and B, so G is just Y minus a small amount of R and B. ![]() On the other end, the television would convert B-Y to B by adding Y to it, and R-Y to R the same way. They combined red (R), green (G), and blue (B) into a luminance, or brightness, channel (called Y for historical reasons), a B-Y channel (called U or Cb depending on the context), and a R-Y channel (called V or Cr). First of all the engineers realized that rather than sending completely separate color and black-and-white signals, they could just add two color-difference channels to the black-and-white channel, and then recombine those three channels into the R, G, and B channels needed for color display. ![]() Given that the original television signal used all the available information-carrying space for its single channel, It seemed impossible to add two more channels, much less keep the signal compatible with everyone’s existing sets. The problem was that the original television signal was designed to send a single channel of information, but producing a vivid full-color image requires three channels: one channel each for red, green, and blue. When color was added to television in the 1950’s, the FCC and the networks wanted to keep the new color signal compatible with all the black-and-white televisions that people already owned. The very first television signals were black and white. If you just want to know how to use the Color And Tint pattern to set Color and Tint, skip ahead to the section called “Using the Color and Tint Pattern.” If Tint isn’t set correctly, all of the colors on the display will be wrong.įirst let’s cover some background about color and video, including why we need Color and Tint adjustments and what, specifically, they adjust. The Tint control (sometimes called “Hue”) is used to adjust the balance between the two chroma channels. ![]() If Color is set too high, the colors on screen will be oversaturated, and if it’s set too low, the colors will be muted and washed out. Samsung tv screen has blue tint.The Color control (sometimes called “Saturation”) is used to adjust the relative balance between the chroma (color) channels and the luma (brightness) channel. ![]()
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