A color bar is an electronic test signal for checking and adjusting television studio equipment. This test signal is also transmitted through the broadcasting and receiving equipment and can be used to check televisions or video recorders.
In the case of the color bar, the order of the colors is specified by the European Broadcasting Union( EBU), and the levels are derived from the luminance and color difference signals.
In the studio environment, the color bar test signal is used for visual verification, but also for voltage and vector measurements. These measurements are performed with oscilloscopes and vectorscopes and show the attenuation of the luminance and chrominance signals and the phase shifts compared to the burst.
Color bars have a step-like brightness gradient, which is shown on the screen falling from left to right, from white (left) through 6 color steps to black. With white, all three primary colors are active, R+G+B, which corresponds to a level of "1".
The color levels correspond to the brightness perception and take place from yellow to cyan, green, magenta, red and blue. If you look at the individual colors in more detail, you will see that the color yellow is a secondary color of additive color mixing, formed from red and green. In the PAL- RGB color wheel, yellow has an angle of 167°. The level of yellow is calculated from the level values of red and green, the angle from the level ratios. According to this, red has a level of 0.299 and green one of 0.587. This results in a level value of 0.89 for yellow. The cyan following the yellow results from the addition of green (level:0.587) and blue (0.114) to 0.70, and so on.