Quote:
Originally Posted by etype2
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If the color bars are generated as R, G, and B = 1(max) or 0, and passed through an NTSC (or PAL) encoder, the electrical composite signal will drive a TV with standard NTSC or PAL decoder to CRT drive values of 1(max) or 0, because the electrical chroma encoder and decoder for PAL was never changed from the NTSC spec. In other words, the Y, R-Y, and B-Y signal values and resulting subcarrier amplitude and phase of NTSC bars and PAL bars are identical, although each primary color is different.
This results in some differences in the brightness of the compatible black and white picture of saturated colors from a camera, but not from color bars, because the matrix for PAL primaries is at a linear signal point just after the pickup devices and before the gamma correction and encoder. The resulting errors on a black and white receiver were considered too small to worry about compared to those caused by use of gamma-corrected R', G', B' to form Y'.
The above is true for analog signals, and for properly encoded digital NTSC and PAL sources.
When the color bars come from a proper digital HDTV signal (as Y', Cr, Cb), the luminance signals are different from NTSC and PAL because the encoding from RGB to Y, Cr, Cb is adjusted for the relative brightness of the HD primaries.
Yes, it's confusing, and provides employment for those who design hardware and software to convert between the standards and make sure the resulting signals are "legal."