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The Video Image

A video image is made up of two quite distinct elements:

- Luminance (Y): This element contains the 625 lines of PAL and SECAM and 525 of NTSC: in other words, the entire field of the image. It also contains synchronisation codes, 50 Hertz for PAL and SECAM, and 60 Hertz for NTSC. Used alone, the Y signal gives a picture in black and white.

- Chrominance (C): This is a coloured mask which is superimposed on the luminance. Chrominance is composed of a blend of the three primary colours: Red (R), Green (G) and Blue (B). they possess several coding frequencies whether they be in PAL, SECAM, NTSC 4.43 or NTSC 3.58 (for the latter, as it happens, the numbers following NTSC express the frequency of chrominance coding.)

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