70 years of color TV – The flicker box became colorful in 1954

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On December 1, 1954, the RCA 21-CT-55 goes on sale in the USA. Its 53-centimetre (21-inch) picture tube makes it the world's first color TV with a screen diagonal that is halfway suitable for a living room. But at a price of 895 US dollars (excluding tax; around 10,500 dollars in today's purchasing power), it is a hard-to-sell piece of luxury. And this despite the fact that RCA has already reduced the price compared to the company's first model: In April of that year, the CT-100 was launched on the market. This first mass-produced color TV in the world had a rather measly gross diagonal of 15 inches (38 centimeters), cost 1000 dollars (2024: around 11,730) and only found around 4,440 buyers in the entire USA.

As astronomical as the prices for a television in 2024 may seem, they were more than justified at the time. RCA not only had to develop a completely new type of picture tube, but also the entire recording and broadcasting chain – and in doing so outperform what at first glance appeared to be an ingeniously simple competitor system.

Television wants color

The situation in the USA after the Second World War was tricky. When the US economy was booming after the end of the war and the electronics industry could no longer focus on radar or radio equipment for the army but on entertainment technology, television, which had just taken flight, was to catch up with cinema and become colorful. The few TV sets and TV services sold before and immediately after the war were all black and white. In cinema, on the other hand, thanks to Technicolor and, in this country, Agfa, color is not dominant – but it becomes more and more commonplace after the end of the war.

For the companies that want to bring color into the living rooms of viewers, this means They not only had to design the right cameras and screens, but also develop suitable transmission technology. At that time, the human sense of color vision had been researched and it was also known that almost all visible colors could be mixed from red, green and blue (RGB). On August 28, 1940, CBS (Columbia Broadcasting System) presented an idea that was as simple as it was seemingly clever: mechanical color TV. If you place an RGB color wheel in front of a black-and-white video camera and a black-and-white screen and rotate it fast enough in front of the recording and playback device, the three sequentially transmitted color separations merge into one color image for the viewer. No new camera technology, no new screens – The biggest, but solvable problem is to synchronize the colour wheels on the camera and screen sides.

Unfortunately only seemingly ingenious

On closer inspection, and even more so in practice, the disadvantages of this idea quickly become apparent: On the receiver side, the color wheel quickly becomes bulky for even halfway usable screen sizes – even alternative drums rotating around the screen are not really compact. The mechanism also makes noise and is subject to wear and tear. Finally, the technology shows edges in all colors of the spectrum – an effect that is also familiar to users of single-chip DLP projectors.

The biggest problem with CBS technology, however, is that the color signal produced in this way is not compatible with the black-and-white televisions that have just been sold – and requires more bandwidth than black-and-white TV for comparable image sharpness ("resolution").

Despite all these shortcomings, the Federal Communications Commission (FCC), the authority responsible for radio and television, declared the CBS system the official color system of the USA in 1950.

Victory thanks to the Soviets

Although rival RCA had presented an alternative –, it was initially so poor that the FCC gratefully rejected it. But because of the Korean War instigated by the Soviet Union, all color television plans were put on hold shortly after the decision in favor of CBS: As in the Second World War, there were more important things than entertainment electronics.

Stalin's warmongering gave RCA the much-needed breathing space. The RCA idea: the color is packed onto the black-and-white signal in a compatible way (details on NTSC transmission here), specially developed color picture tubes show the signal transmitted in this way without wheel mimicry.

The picture tubes are the crux of the matter. Black and white copies are comparatively simple. The inside of the picture side is coated with phosphor, opposite it sits an electron source in the tube neck. Electromagnets ("deflection coils") controlled by the image signal move an electron beam across the luminous layer, the voltage of which is proportional to the image brightness. The image is written line by line from top to bottom in the luminous layer; the phosphor's afterglow and the inertia of the human visual system trick the eyes into believing that the image is a complete moving image.

But when a picture tube is supposed to show color images, things get complex. The smallest, but by no means trivial, problem is to accommodate three electron guns for RGB in the tube neck instead of one and to control them independently of each other, but still synchronously. Around 150 individual parts need to be in the right place in the tube neck.

The picture side is much more difficult: instead of a uniform luminous layer, different phosphors in the three basic colors need to be applied to the inside of the tube in a neatly separated manner. Each RGB triplet represents a luminous dot. Even if you can see and count the triplets: They do not correspond to the discrete pixels of modern flat-panel displays.

The shadow brings it to light

Once the three electron sources have been accommodated and three different phosphors applied, there is only one problem left to solve: How do you ensure that each electron gun only hits the color dots intended for it? Without further ado, each electron beam would excite all RGB triplets to glow – goodbye, color image...

This problem is solved by a shadow mask, also known as a shadow mask, placed in front of the luminous layer in the tube. It ensures that each electron source sees the light spots intended for it. The production of such a picture tube is a lengthy process – is explained in this RCA film:

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In the first picture tubes produced by RCA and others, the triplets are triangular in shape, and the electron guns are also mounted in the neck of the tube in the shape of a triangle. The biggest problem in production is to adjust the RGB electron guns so that they cover the entire surface of the screen ("convergent"). This requires patient adjustment...

Dark figures

On the other hand, another problem cannot be eliminated: the shadow mask lives up to its name, as it swallows around 85 percent of the energy and therefore brightness of the electron guns. The early color picture tubes are real sparklers. Nevertheless, NTSC and the RCA picture tubes worked well enough for the FCC to change its mind at the end of 1953: The fundamental disadvantages of the CBS system could not be overlooked; despite the still modest picture tubes, the regulators declared the RCA system the US color TV standard on December 18, 1953.

A third team around the film studio Paramount and the nuclear physicist Ernest Orlando Lawrence was also involved in this, as it had a similar idea for transmission technology to RCA's NTSC – and, like RCA, lobbied for a black-and-white-compatible electronic system. But as a picture tube, they have a model called Chromatron. If it worked, it would be vastly superior to the RCA design with shadow mask – and when Sony's laboratory manager Nobutoshi Kihara saw an example of this display at the "IRE Show" science exhibition in 1961, he was so convinced that Sony secured the rights to it. It soon became clear that the production of this type of tube was a nightmare. Sony was almost ruined – and it was only when the idea was modified in 1966 to create the Trinitron tube that it became a technical masterpiece that brought Sony good money for decades.

Color TVs without a program

Until then, however, there was only the RCA tube, which was of course also optimized. But the color TVs that appeared in 1954 and the years that followed were not only plagued by the teething troubles of many technical innovations: There is simply hardly any programming in color and thus the typical chicken-and-egg problem. No program – no incentive to buy a colour TV. No color TVs for the audience – no incentive for broadcasters to produce color programs.

The fact that RCA owned one of the three nationwide broadcasting chains, the National Broadcasting Company (NBC), did not help much at first. It was not until 1962 that NBC also began showing two thirds of its evening programming in color. The competition is even more hesitant – It takes until well into the 1960s for substantial parts of US TV programming to be in color and for a sufficiently large number of customers to opt for a color set. In 1966, with 5.8 million televisions, more color sets were sold than black and white sets for the first time.

Europe also tinkered with the color TV picture

At that time, Henri de France was also working on the Secam color system in France and Walter Bruch was working on PAL at Telefunken in what was then West Germany. This started in West Germany in 1967 – Although the USA had laid the foundations with its work on color television, it ultimately launched the technology prematurely.

Nevertheless, the investment of 40 million US dollars at the time paid off for RCA: Even though no country of importance at the time apart from Japan and Canada accepted the NTSC transmission system developed by RCA: RCA had all the important patents for color picture tubes for decades, as well as for the machines for color picture tube production. Even after Sony's Trinitron breakthrough, this situation did not ease for all other TV and CRT manufacturers, as Sony kept the technology for itself – only computer monitor manufacturers were supplied with Trinitron CRTs.

The present is flat

Over the years, however, other manufacturers also dramatically improved the technology of color picture tubes. Instead of arranging the electron guns in a triangle, they were placed next to each other ("in-line"), and the RGB phosphors for each triplet were no longer arranged in triangles but next to each other. Heat-resistant shadow masks allow higher beam currents and therefore more brightness. Around the noughties, the display sides of picture tubes were basically rectangular and flat – The first RCA tubes were not only strongly curved, but also round, which meant that part of the tube surface could not be used for the picture. With the first HDTV attempts in Japan, picture tubes also became high-resolution and were given the more cinema-oriented 16:9 format.

But it's clear: to really immerse yourself in the action, you need larger displays – which are almost impossible to achieve with CRT technology because they are too heavy, too expensive and too sensitive. But that's what LCD, plasma and OLED screens are for...

Until then, RCA benefited for decades from its pioneering work in color television. However, in the 1960s, the company's top managers lost their flair for future technologies: one of the first liquid crystal displays was presented as early as 1968. But the chemicals required for this were not to be handled. They are too dirty for the bosses – in view of the substances required for color picture tubes, including lead for the glass, a rather unworldly view. The biggest nail in the coffin, however, was a picture plate that had been misplaced for decades. As with so many once renowned companies, only the name of RCA still exists.

(nie)