Could NTSC VIR = PAL

[old_tv_nut]

Another note regarding the mismatch of re-inserted burst to chroma amplitude distorted by network transmission:

The two major US TV makers, Zenith and RCA, had different philosophies in this regard.
Zenith used the burst as automatic color level reference, as this took out the final transmission variations due to ghosts, airplane flutter, etc. However, this ignored the network distortions. RCA's auto color mode worked on the average chroma level of the picture. They felt this was an overall improvement, although it meant the color level could be affected adversely by overcompensating for scenes either with large areas of bright colors or with no saturated colors. The general public seemed to be accepting of these "subject errors." They bothered me, though, and I always preferred to run the RCA sets with auto color off for this reason. Unfortunately, this meant also losing RCA's superior auto hue ("tint") correction, which actually had been invented by a colleague of mine at Motorola and was licensed to RCA. It worked only on hues near flesh tone, and didn't destroy greens and purples the way other makers' auto tint did. Motorola, by the way, never used their own invention.

[NewVista]

Originally Posted by old_tv_nut

..RCA's superior auto hue ("tint") correction, ...worked only on hues near flesh tones.

How on earth did this work?

[old_tv_nut]

Originally Posted by NewVista

How on earth did this work?

The usual auto tint worked by changing the angles, and possibly the gains, of the color demodulators. The result was a reduction in saturation of greens and magentas, plus colors that were near orange or cyan had any green or magenta component reduced. If you picture a circular color wheel (or a gated-rainbow test pattern), the circle got compressed into an ellipse.
Thus, all colors were distorted to be closer to flesh tone or cyan, or at least a weaker green or purple.

The RCA circuit worked on the phase of the oscillator output going to the demodulators. The nearer the chroma phase was to flesh tone, the more strongly it was pulled towards flesh phase (hue). If it was already a flesh hue, this made no difference. If it was close, it was pulled strongly towards flesh. If it was further away, it was pulled less. So, yellows were made a bit more orange, but greens weren't significantly changed. Similarly, reds were pulled toward orange-red, magentas were pulled a bit towards red, but purples were changed even less if at all. Since this change was phase only, it didn't affect the saturation of greens, purples, or any color, for that matter.