Also the chroma (4.43 MHz subcarrier) was visible[1] on B&W sets and could be somewhat annoying, especially so on those with good focus and resolution. Moreover, by the time colour was introduced B&W sets had progressed to having quite reasonable resolution and could easily display content with a resolution of 4.43MHz.

These 'artifacts' would be made worse when optical herringbone effects, etc. were generated from the mixing of the visible subcarrier with certain types of image content such as striped suits or any content containing closely spaced lines of reasonably high contrast.

This type of content was always a worry even before the colour/subcarrier issue as it could mix with the scan lines to produce unpleasant optical beating-type effects.

Some TV stations even had dress code policies to avoid the problem but they were often ignored even before colour was introduced (it's often a bit tricky to tell an important dignitary to change his suit or striped tie before he appears on camera). :-)

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[1] Note: in colour TV sets the chroma subcarrier is intrinsically suppressed by the PAL system (which converts the S/C to colour info) although some artifacts remain because of bandwidth, switching issues and other system limitations.

It should be remembered early TV systems faced huge engineering obstacles and the 405, 525, CCIR 625 and 819-line system standards were remarkable engineering developments in their own right given the engineering strictures of the time - so colour wasn't on the agenda when they were developed.

Essentially, colour was an afterthought that had to be retrofitted to and be compatible with these existing B&W television standards.

The biggest problem was that the colour subsystem had to be fitted within the existing broadcast spectrum, that being the bandwidth of a TV channel which was typically 6, 7 or 8 MHz depending on system or country. And back then this was no easy feat.

Moreover, squeezing in colour became an even bigger challenge given that bandwidth-limiting techniques were already being employed to reduce spectrum usage, for instance, interlaced scanning and broadcasting video in reduced-bandwidth vestigial sideband.

Overcoming the bandwidth-limitation challenge posed formidable problems but eventually cleaver minds solved them with some ingenious solutions the first of which was the NTSC Color System. It was followed up with SECAM and PAL which were in essence variants of NTSC and the raison d'être for their development was to overcome NTSC's 'phase' problem wherein colours could easily drift from the original.

SECAM and PAL had ingenious but quite different ways of 'clamping' down this 'phase-shifting' problem and both were successful at doing so. Leaving national interests/pride aside (SECAM-Fr, PAL-Deu), arguments over which scheme was best revolved around considerations of the technical issues such as bandwidth tradeoff versus amount of phase shift correction that was deemed possible and such. Also included were matters such as the amount of residual artifacts that the colour information would introduce into the main luminance component.

Now, I'm not going to get into that perennial debate about whether SECAM or PAL is better except to say that my primary television experience was gained from working within a CCIR-625/PAL environment and it's a excellent system. But then so is SECAM excellent, and I can attest to that having spent considerable time in France watching it.

The US NTSC Color Standard often comes in for criticism but I reckon that's unfair given it was the first. Moreover, it has one significant advantage over the other two and that is its 60 Hz frame rate (the others being 50 Hz). I noticed the difference this makes when years ago I first visited the US: almost my first perception of the country happened at Los Angeles airport when I noticed that the airport's monitors weren't flickering (which is a significant annoyance in 50 Hz systems)!

A final point: when considering TV encoding systems we cannot forget Nyquist and cohorts who made all that information-squeezing possible, similarly so Shannon whose brilliant ideas have gone into the development of the encoding schemes now used in our modems and digital audio and television systems.

It seems to me that advances in encoding techniques were essentially just as important as they they were in image sensor development. Both technologies are essential and integral parts of modern digital television, thus developments in both were of critical importance for DTV's development.

Incidentally, the first colour TV camera I examined close up was a huge and almost unmanageable beast made by RCA. It used three separate vidicons for the chroma channels and an image orthicon for the luminance. Whenever, I look at the camera in my smartphone I never cease to be amazed at the progress we've made in these technologies over the past 50 or so years.