Early colour TV experiments.

[Geordie McBoyne]

J. L. Baird used only two colours for his first electronic colour TV experiments.   A reasonable colour TV picture can be realised by employing cyan and magenta, obviously it's not going to be as good as RGB.                                                                              Found this in a Wkipedia topic about Telechrome:

Baird's comments at the time of introduction generally spoke of a two-color, 1,000-line resolution signal. This would have required considerable radio bandwidth and would be incompatible with the pre-war 405-line system introduced by EMI and the BBC. However, in the patent application he also considered the possibility of compatible color systems. One would use either frame of the existing interlaced image for each color, although this would reduce the effective resolution from 405 to 202 lines, and the frame rate from 50 to 25 fps which would increase flicker in areas of mixed color. He also mentions a system broadcasting full 405-line images, but at even greater reduction in frame rate to 12.5 fps, which is noted would cause considerable flicker.

From the ETF:  http://www.earlytelevision.org/baird_ele..._color.htm

Would be a real fun project for someone with the spare time two create a two colour TV system, either mechanical or electronic.

Geordie McBoyne.

[Mike Watterson]

Really I think Baird is credited with boosting the idea of TV, and actually the only really good thing he did was the near real time film to to scanner camera system, later used on satellites to solve the problem of getting back high resolution images from space.

Long before Baird's colour Experiments the RGB had been done and transmitted in early 1930s (mechanical) and his mechanical system was 30 years behind the ideas of TV (fully Electronic TV proposed in 1905, only lacked a mechanism to store the image as charge), and Baird's system was basically Victorian. I've never understood why he is lauded more than the successful more clued up pioneers who actually were properly educated and understood what they were doing.

Two colour systems had already been shown to be a failure in printing and photography in the Victorian era. What held colour photography back was getting decent red sensitivity in the film.

Farnsworth is the USA equivalent. His camera system was inherently a failure compared with the stored charge concept and was never going to be more than a lab curiosity.

[ppppenguin]

2 colour film systems persisted until about 1930: https://en.wikipedia.org/wiki/Technicolor

Baird first showed colour experiments in 1928, using 3 spirals on a single scanning disc.

Campbell Swinton's 1908 and 1911 proposals for all electronic TV https://en.wikipedia.org/wiki/Alan_Archi...ll-Swinton suffered primarily from lack of any kind of workable camera tube.

Farnsworth's image dissector tube lacked charge storage and hence was very insensitive. However it was developed for specialist applications where there was plenty of light and its simple, rugged design made it suitable.

[Raditechman]

I think one of the last films to use a 2 colour sytem was "Jack and the Beanstalk" with Abbott and Costello, year 1952.
Filmed in SuperCineColor, which was a 2 colour process.
You can watch it on You Tube and see what the 2 colour results achieve. Wait for the opening book credits to finish to see the colors.
https://www.youtube.com/watch?v=rHBOWus04gk

John

[Murphyv310]

Hi.
You need to wait till the credits and the "modern" section (Sepia) finishes before you reach the colour part.
The overall result is actually OK, not as good as what we are used to now but considering the process it is acceptable.
I'm sure at the time Colour TV would have still sold just as well using the two colour system as RGB.

[ppppenguin]

A 2 colour TV system would hardly have been future proof. NTSC (also PAL and SECAM which ultimately derive from NTSC) all showed their long term potential. We've only recently stopped using them and they are still around in a lot of CCTV systems and legacy video connections.

In Mertz and Gray's famous 1934 paper in Bell System Tech Journal they make an interesting prophecy. See the attached image: "These idle frequency regions...." That's exactly where NTSC and PAL put the colour information.

There's also that immortal quote: "The horse always looked good".

[Murphyv310]

Yes I agree that the two colour systems would hardly be future proof but consider the following:
405 line TV
VHS
Beta
Valves
Car engines with points

There are many things that have gone so you could easily say none of the above were future proof. We have to look at things from the perspective of the times not from today's viewpoint.
I'm sure the two colour system could have been right at the time as was 405 lines even post war but to look at 405 now it would have been a joke just like two colour TV.

[ppppenguin]

It's always hard to know what's right at the time. The French took a jump too far with their ambitious 819 line system. The Americans got it badly wrong with CBS sequential color. We probably got it right by staying with 405 in 1946 but it's debatable. In 1936 405 was definitely a system designed with an eye to the future, by 1946 that was no longer certain. Philips had the world's first workable domestic video recording format (N1500) but it rapidly fell victim to VHS and Beta.

Interlace was a brilliant compression system at the time. Now it's only a hassle as it's hard to unpick it accurately.

[Murphyv310]

Interlace was a brilliant compression system at the time. Now it's only a hassle as it's hard to unpick it accurately.

It was Jeffrey.
I wonder if those Computer Models that electronics are designed on have forgotten about the interlace diode?

[ppppenguin]

Although not explicitly covered in the Mertz and Gray paper I mentioned before, the problems of interlace can be worked out from their maths. The underlying problem is that vertical and temporal information get mixed up and can be very hard to separate accurately. In some cases it's impossible to do so and the best you can do is fudge it.

Of course on it only gives enhanced vertical resolution on still pictures. As soon as you get movement on 405 you're down to 202.5 lines, less than Baird's 240 line progressive.