[somat]

The article also raises an interesting question. My understanding is the big difference in North American and British color TV is that NTSC was engineered to be backwards compatible with existing black and white broadcasting standards, this is the source of many of it's sins. While the British system was able to both learn from ntsc's problems and make a cleaner break from black and white.

I guess the question unanswered in the article is did this have anything to do with camera tech used? (4 vs 3 tube)

Well, off the scour the dusty corners of the web to try and learn more about early color television.

[kmeisthax]

AFAIK no - in both NTSC and PAL you're transmitting a monochrome signal plus some extra analog information that encodes two additional color channels. The difference between NTSC and PAL is primarily the framerate and the color encoding method: PAL encodes color in a slightly different way (by Alternating the Phase on each Line) that's more robust to analog distortion. But it's still ultimately encoded as a color subcarrier on top of a black-and-white signal. The only relevance the 4-tube cameras have to the story is that they provided an easy and convenient way for striking camera operators to kill color.

The big sin in NTSC is the 59.94fps field rate. This is because NTSC transmitted on 6MHz channels that were fully utilized, there was no space for color. A naive implementation of this at 60hz field rate would mean beat frequencies with the audio carrier, giving visible dot patterns in the signal. Slowing down the field rate got rid of that interference.

PAL was based off an existing German 625-line system that was transmitted on wider channels, so they had extra bandwidth. No slowdown was required. But at the same time PAL was not a clean break, nor was it British. It's a German standard that applies the same general idea as NTSC[0] to German B&W. It was only a clean break in that didn't use the UK or French systems[1], which were either too low or too high resolution to be practical for 1960s color tubes.

[0] If you want to see a real sin, go take a look at the alternate history of interlaced-color TV that NTSC saved us from. NTSC is a sin in the same way that putting the Red Cross logo on a health pack in a videogame is technically a war crime.

[1] Which, to be clear, also had enough bandwidth for color without a beat frequency.

[jordanb]

NTSC's problems versus PAL is more of a first-mover problem. NTSC was standardized a decade before PAL so the technology wasn't as advanced, and the PAL authors got to see NTSC get implemented. But by the time PAL was implemented NTSC was already entrenched in North America and some other markets and PAL's superiority wasn't sufficient to get people to abandon the older standard.

[adrianmonk]

I'm no expert on cameras, but this seems to explain it:

https://en.wikipedia.org/wiki/Four-tube_television_camera

This says the main reason for four-tube is image registration. Basically, the incoming light is optically split up into red, green, and blue, and these go to separate sensors. Being separate sensors, they may not be physically aligned. So if you sum R + G + B together to get luminance, the picture will not be sharp.

You can solve this by adding a fourth (black and white) tube for luminance. Since it's just one tube, there is no alignment issue for the luminance part of the picture. And the eye is less sensitive to color, so while the color alignment issues remain, they aren't very noticeable.

At first when I read this, I assume the camera must have to somehow combine the fourth tube's signal with the other three tubes' signals. But since both NTSC and PAL encode luminance and chrominance separately, apparently this isn't necessary. It's the TV that combines them. With a three-tube camera, the sensor signals have to be split into luminance and chrominance. With a four-tube camera, you just take luminance from one sensor and chrominance from the other three sensors.

[hdgvhicv]

Not really, pa will show up fine on a black and white tv, as the chroma is lost in the line blanking. Some very poor b+w tvs with terrible filters might show a little high frequency noise but that’s it.

The big difference in the U.K. is that 405 lines was on vhf channels. The move to colour was also a move to pal, 625 and uhf.

625 lime receivers came out in the early 60s, and typically would also work with 525. Bbc 2 launched on 625 in black and white in 1964 I think, but didn’t add colour until 1967. 405 only sets stopped being sold by the end of the 60s.

Only bbc1 and itv transmitted 405, but continued until the 1980s. Most 625 sets were black and white 625 lines, and that slowly changed during the 70s.

A 625 black and white set from 1965 could pick up tv signals and display them fine (in b&w) until analog switch off around 2010 (phased across the country. The final 405 lines worked for 20 years.

Like ntsc colour was a sub carrier which exposed the colour difference signals. Unlike ntsc, pal switched the Phase on Alternate Lines, so reflections and other signal interference canceled out, like it does with balanced audio (and indeed balanced data in cat5 cables). NTSC didn’t have this correction so sets had a “tint” control to adjust the signal.

This led to the moniker “never twice the same color” for ntsc.

[ErroneousBosh]

> Some very poor b+w tvs with terrible filters might show a little high frequency noise but that’s it.

A lot of 1980s home computers had such intense colour saturation that you could also just about tell what colour something was supposed to be from the cross-hatch pattern on a black-and-white set.

There was an interesting bit of work done about 20 years ago where a team from the BBC were able to recover colour from programmes that only existed as black-and-white 16mm film used for broadcast logging. These were filmed off black-and-white monitors (nice and sharp!) onto fairly slow film (not too grainy!) from a colour feed, and by decoding the colour intermod that's visible on a really high-quality scan of the film it's possible to recover colour information.

Well nearly.

The burst is lost in the line blanking as you say so although the chroma is present across the line there's no phase reference, so it's impossible to tell which "handedness" the colour is. But that's okay, one way round everyone looks sickly greeny-blue and the other way round everyone looks normalish.

Much of the trick relied on calibrating it against footage for which Format C colour video (a raw baseband recording, no colour downmixing like for say VHS) and 16mm B&W film existed, which brings up the unfortunate part - the absolute best examples of that are a couple of episodes of Top of the Pops, presented by the late Jimmy Savile.

Bit of a pity it wasn't maybe Janice Long or Bruno Brookes really.

[netsharc]

For a bit of trivia, David Attenborough has won an award for his work in each of the formats: B&W, color, HD, 3D, 4K.

[leoc]

He made snooker a (relatively) big sport by putting it on TV https://en.wikipedia.org/wiki/Pot_Black because he needed something which would advertise the benefits of colour TV. The matches needed literal-not-metaphorical colour commentary for those on B&W sets, leading to the famous gaffe "Steve is going for the pink ball - and for those of you who are watching in black and white, the pink is next to the green." http://news.bbc.co.uk/2/hi/entertainment/3629569.stm . The theme music was the "Black and White Rag" https://www.youtube.com/watch?v=4ri3utpSoRA .

[chadgpt3]

Chroma is not lost in line blanking. It creates dots that crawl across the screen.

[hdgvhicv]

Yes the high frequency noise. Depends on how good the hf filter is.

[chadgpt3]

Why would you have one? Want the image to look blurrier on purpose? Color TVs have one to block the color dots.

[Majromax]

If you're deliberately displaying the image in black and white, the colour pattern is interference that should be suppressed.

However, this practice was not universal, and archivists have now recreated colour copies (https://en.wikipedia.org/wiki/Colour_recovery) of some shows where only black and white recordings survived by reconstructing the colour from these interference signals.

[actionfromafar]

A very late in the signal chain color decoding. :-D

[ErroneousBosh]

There's no real luminance content above about 5MHz, and TVs used to notch out the colour at 4.43MHz.

As an aside, you can do all this digitally now with phenomenally sharp results.

[Honali]

Early color TV is one of those topics where every answer seems to open three more trapdoors