|MadSci Network: Computer Science|
Assuming your TV is built using a CRT (Cathode Ray Tube): The image of a CRT is created by a scanning electron beam, which excites the substances on the inner wall of the front glass to emit visible light via phosphorescence. A fine raster of different substances will light up in the colors red, green and blue, which causes you to perceive a color image. If the electron beam always hits the same dots (e.g. a purely blue area of a video game background), then these surface points age faster (i.e. their capability to phosporesce diminishes over time). Over several months of operation this can create a visible difference in areas of the screen, when a picture with little details and large monochrome parts is displayed. So indeed playing video games or leaving any static screens on the TV for long hours has a negative impact on color uniformity across the screen. However, more likely the color hues, which you describe, are induced by strong magnetic fields in the environment of the TV. The magnetic field causes the electron beam to miss the targeted points and excite points around it. Just take any strong magnet and bring it near the screen to see this effect. [Admin Note: if you bring it too near for more than a second or so, it can cause permanent damage to the monitor; you might want to try this with an old tv or monitor instead. -- RJS] The cause can be in the near surroundings (e.g. a power supply with a big improperly shielded transformer near the TV) or even outside the building (e.g. people living very close to electrical train tracks can have this problem every time a train passes by). Certainly a defect in the TV itself can also affect the electron beam and cause color hues. Temporary color hue changes can also happen, when the signal from the sender to the antenna is affected. A technique to prevent this is used in the European TV systems (PAL, phase alternated lines). The US is still not using this technique. So as a joke the acromym NTSC of the US TV system can be expanded to "Never The Same Color".
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