Cinematography-Theory-And-Practice

Figure 9.21. (above) The Chromadu Monde test chart from DSC labs:an 11 stop gray scale surroundedby color patches of the primary andsecondary colors.Figure 9.22. (left, top) The Chromadu Monde on the vectorscope in Rec709 color space.Figure 9.23. (left, bottom) The samechart rendered in a different colorspace — in this case, NTSC.Analog/Digital ConversionConversion of the video signal from analog to digital occurs inthree parts; signal preparation, sampling, and quantization (digitizing).There are two types of component signals; Red, Green, andBlue (RGB), and Y, R-Y, B-Y, but it is the latter that is by far themost widely used in digital video. R-Y and B-Y, the color differencesignals, carry the color information, while Y represents the luminance.Cameras, telecine, and so on, generally produce RGB signalsat the sensors, but it is almost always converted to another formatbefore output because an RGB signal is far too much informationfor recording.DIGITAL VIDEO ENCODINGDigital video is fundamentally different from NTSC and PAL videoin the way it is encoded and processed. Various types of processingequipment manage the digital video in different ways. These areclassified by the way in which they encode the information.4:2:2This is a set of frequencies in the ratio 4:2:2, used to digitize theluminance and color difference components (Y, R-Y, B-Y) of avideo signal. For every four luminance digital samples, there are twodigital samples of each color difference channel. The human eye isnot as sensitive to color as to luminance detail, enabling this formHD cinematography165