Color TV Has a Problem
May 1966 Radio-Electronics

May 1966 Radio-Electronics [Table of Contents] Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Electronics, published 1930-1988. All copyrights hereby acknowledged.

Color TV has reached nearly 5 million American homes, but many viewers complain about inaccurate colors due to chroma-phase differences among networks, stations, and cameras. This results in annoying hue changes, making it difficult for viewers to adjust the Hue or Tint control for accurate flesh tones. This 1966 Radio-Electronics magazine article suggests three possible solutions to this problem, emphasizing the need for precise phase agreement among all components of the color TV system. Solving this issue could encourage more people to adopt color TV technology, as the annoyance of inconsistent colors is one of the last reasons the public has found for not making color-TV ownership unanimous. Still plaguing the color TV industry is powerful x-rays emanating from the high voltage power supply.

Color TV Has a Problem

by Forest H. Belt

Color TV has invaded nearly 5 million American homes, a little less than 10% of all that have television. Why don't the other 90% have color?

One factor is no doubt cost. But, color receivers are available now priced lower than many monochrome models - often less than small-screen monochrome sets were priced only a few years ago. If you question those who can afford color, yet don't have it, a common answer goes: "I don't like the pictures. The colors aren't true."

Their complaint is well founded. Today's most annoying color-TV problem is caused by slight chroma-phase differences among the three networks, among stations, from film chain to film chain - even from camera to camera in the same studio. No matter how carefully chroma phase is adjusted in each, these few degrees of difference create annoying hue changes for viewers.

No sooner does a color-TV viewer get the HUE or TINT control set for a good flesh tone than the scene changes to another camera and some actor's face turns sickly green; another camera change is just as likely to make a fair-skinned starlet look purple.

And the flesh tone itself poses a slight difficulty. What if the actor has a deep tan? Or, suppose a dancer is momentarily flushed with excitement or from exertion in the preceding scene. Under either circumstance, adjusting hue - even in a closeup - is anything but precise. Then, before the viewer can hardly move the knob, the scene may become a fast-action sequence and further adjustment is impossible.

There's been a tendency to pretend, at least publicly, that the problem doesn't really exist. But it does nevertheless, and mass magazines and newspapers have been needling the industry because of it. We may as well face this inherent problem and set about solving it.

What color television needs now is some way to assure precise phase agreement among the 3.579545-MHz bursts at all cameras, film chains, stations, networks, and color sets. At least three approaches come to mind, and there must be many more.

One possibility would involve a Standard Hue Card and a resulting Standard Hue Signal. The card might contain seven bars: black, yellow, black, flesh, black, white, and black. Every studio camera and film chain would be set up initially to reproduce this Standard Card faithfully, and then would be fed the Standard Hue Signal automatically between "takes" so the operator could match the card at all times, thus maintaining a standard, precise phase alignment. The Standard Hue Card could be flashed for a few seconds at the start of each show, before or after each commercial, and with each station-ident card, for viewers to use and for checking retransmission. All local stations and network relay points would make sure they were duplicating the Standard Hue Signal exactly each time it was transmitted. Such a system would be complex, but might be workable with proper cooperation and coordination.

A second possibility is a 3.579545-MHz standard signal, critically phase-controlled throughout the US by some primary source such as WWV. If chroma from all color-TV stations were phase-locked to this single primary source, one setting of the HUE or TINT control at any color receiver should hold the colors true for all programs.

A third idea could be used with either of the other two approaches or (perhaps better) could be developed to function independently. This would be a circuit or device that automatically compensates for any color-phase variation - right in the color receiver! This approach would eliminate some of the worry about phase differences at points of program origin. Solving the phase-difference problem at the receiving end would be the most satisfactory way from many points of view, although it is merely "wiring around the trouble" rather than curing the trouble itself.

There are undoubtedly other approaches. The important thing is not really how it's done. What is important is the challenge this color-phase problem lays before the designers of tomorrow's color-TV receivers. Whoever devises a workable solution will eliminate one of the last reasons the public has found for not making color-TV ownership unanimous.