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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.
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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.
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