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Old 06-18-2020, 09:38 PM
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1953 NTSC Color Gamut

I read that the first official Color Gamut Standard for displays was the NTSC Color Gamut, which made its debut in 1953 for the beginning of US color television broadcasting.

Was there ever any 1953 NTSC color consumer or professional content based on the true NTSC Color Gamut and if so, are there photographs displaying the wide color gamut on a CRT?
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Old 06-18-2020, 10:53 PM
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Originally Posted by etype2 View Post
Was there ever any 1953 NTSC color consumer or professional content based on the true NTSC Color Gamut and if so, are there photographs displaying the wide color gamut on a CRT?
I'm not sure what you mean by consumer content. In 1953 only professional cameras were available.

The original RCA TK-41 cameras were designed to come as close as possible to correct for driving a display with NTSC phosphors. Calculations based on spectral sensitivity measurements (rescued from loss at RCA) show this.
http://www.bretl.com/viewing1950scolor.htm
This was achieved with narrow-band optical filters and no electrical matrixing, as that would have brought on increased noise and stability problems. The result is that very slight adjustments in the color level and hue settings of a receiver/monitor would produce excellent color matches for common surface colors, better than any photographic film. However, the cameras also had less gamma correction than required to match the CRT gamma, resulting in increased contrast and color saturation. The cameras thus had a problem of limited dynamic range (as did the CRTs if viewed in a lighted room). The system was similar to Technicolor film in this regard, requiring reduced lighting ratios, substitution of grayed or light blue shirts for white, etc., along with very careful exposure adjustment to put the subjects in the middle of the gray scale.

Later cameras with less noisy pickup tubes and wider bandwidth color optics used electrical matrixing, but it was still set to NTSC specs at first. Meanwhile, display makers had adopted non-standard phosphors and electrical matrixing to keep the hue spread proper between red, yellow and green (and fleshtone). And while camera makers kept the matrix for NTSC at first, they also played with the color separation optics to get the best looking color on monitors, and eventually fudged things entirely to look good on more modern monitors, which had the new phosphors, but a matrix on/off switch. Which position of the switch was the camera fudged for? No one knows what a particular brand of camera did anymore, and it may have been a compromise. One of the glaring problems with the receiver/monitor matrix is that it exaggerated the brightness of reds and reduced subtle variations in them.

All the above mess happened with NTSC. With PAL, because it was established after the new phosphors were usual, the PAL camera optics and matrix was specified to get a proper match without the approximate electrical matrix in the receiver. This practice was incorporated in HDTV and the sRGB still picture standard for computers.

If your question is, is there any material available now that you could play on an early set with NTSC phosphors and know you are seeing NTSC color, the answer in some cases is probably not, and in other cases definitely not. You often can see the high contrast and noise of TK-41s in DVDs of old shows from the early 60s or earlier, but the color may or may not reflect the TK-41s accurately, depending on how much color correction was done in remastering, which of course would have been judged on a modern monitor.

Any of our favorite DVD or Blu-Ray movies for demonstrating old sets are far removed from NTSC. You may see the brilliant emerald greens, but there is no way of knowing if they are correct, because these have all been remastered for current receivers/monitors.

Quote:
Originally Posted by etype2 View Post
... are there photographs displaying the wide color gamut on a CRT?
No.
Color film could not reproduce the NTSC green. Modern monitors cannot reproduce it, and therefore digital photos generally do not reproduce it. As stated above, it is outside the sRGB color space. Thus, when you post jpg files to the web, the viewers really can't see an accurate reproduction of what you had on your NTSC screen.

If you put color bars on your old set, take a picture with a digital camera set to Adobe RGB or prophoto RGB, and display it on a wide-gamut monitor (or the old TV), then you should see the NTSC primaries and secondaries reproduced, sort of. There are many caveats about how the raw data is processed by the digital camera or raw-file processing program, all of which are fudged to get a preferred film-like reproduction rather than a colorimetrically accurate one. Still camera makers and Adobe tumbled to the fact that a film-like "S-curve" contrast response is greatly preferred over the older video camera gamma curve that clipped overexposed highlights.

What to do? Turn on your set, play whatever you like, adjust for best looking results, and enjoy.

I haven't looked lately to see if Photoshop and Lightroom have an NTSC monitor profile available, but if they do and you have an NTSC composite output on your computer, you could display stills from raw files that are close to correct. Failing that, Adobe RGB profile would be close in the reds and greens, but not so great in the blues.
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Old 06-19-2020, 12:47 AM
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That's a pretty comprehensive summary of the issue. The only thing missing is WHY the reference primaries were changed. AFAIK it's because the original NTSC phosphors resulted in pictures that weren't very bright. Newer phosphors were brighter but couldn't give the same range of colours. Since the new colour gamut was good enough it became the standard.

By the time of PAL and SECAM all this had more or less settled down. Not quite though. There was a set of EBU reference primaries that turned out to be expensive and/or hard to make as phosphors. So in practice most CRTs had slightly different primaries. AFAIK it was only a small difference and didn't really matter outside of very critical colour matching.
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Old 06-19-2020, 07:13 AM
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“‘If you put color bars on your old set, take a picture with a digital camera set to Adobe RGB or prophoto RGB, and display it on a wide-gamut monitor (or the old TV), then you should see the NTSC primaries and secondaries reproduced, sort of.”

THE COLOR BARS TODAY WOULD BE SMPTE C, RIGHT?

It’s interesting after 67 years, the original NTSC color gamut has not been exceeded. RCA had lofty goals in the design of the CT-100, then dumbed down later receivers. The consumer was never going to notice the difference and “brighter was better.” The 1953 NTSC color gamut was actually a format that was never used. Excellent paper

Edit: May I consider the color charts in your paper, especially green accurate 1953 NTSC colors? Like this one?https://visions4netjournal.com/wp-co...24396ECF8.jpeg
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Old 06-19-2020, 10:38 AM
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Quote:
Originally Posted by etype2 View Post
...

THE COLOR BARS TODAY WOULD BE SMPTE C, RIGHT?

...
Edit: May I consider the color charts in your paper, especially green accurate 1953 NTSC colors? Like this one?https://visions4netjournal.com/wp-co...24396ECF8.jpeg
If the color bars are generated as R, G, and B = 1(max) or 0, and passed through an NTSC (or PAL) encoder, the electrical composite signal will drive a TV with standard NTSC or PAL decoder to CRT drive values of 1(max) or 0, because the electrical chroma encoder and decoder for PAL was never changed from the NTSC spec. In other words, the Y, R-Y, and B-Y signal values and resulting subcarrier amplitude and phase of NTSC bars and PAL bars are identical, although each primary color is different.

This results in some differences in the brightness of the compatible black and white picture of saturated colors from a camera, but not from color bars, because the matrix for PAL primaries is at a linear signal point just after the pickup devices and before the gamma correction and encoder. The resulting errors on a black and white receiver were considered too small to worry about compared to those caused by use of gamma-corrected R', G', B' to form Y'.

The above is true for analog signals, and for properly encoded digital NTSC and PAL sources.

When the color bars come from a proper digital HDTV signal (as Y', Cr, Cb), the luminance signals are different from NTSC and PAL because the encoding from RGB to Y, Cr, Cb is adjusted for the relative brightness of the HD primaries.

Yes, it's confusing, and provides employment for those who design hardware and software to convert between the standards and make sure the resulting signals are "legal."
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Old 06-19-2020, 10:57 AM
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The graphics in my paper are adjusted to be correct for an sRGB monitor. The colors on the MacBeth colorchecker chart are within sRGB, except for the cyan, which is only slightly outside. The MacBeth green is nowhere near NTSC green. This illustrates how the NTSC primaries do a very good job of covering the gamut of real surface colors, and sRGB does an adequate job.

When I was on the NTSC monitor committee at SMPTE, NBC/RCA set up a test with some brightly colored objects, which were displayed on two identical monitors, except that the CRTs had been made by Sylvania with one being essentially SMPTE C and the other having NTSC green. There was a skein of kelly-green yarn that had been found that was specifically outside the modern phosphor range. I do not recall any cyan object that was outside the range. We then compared the two renditions side by side, including turning the monitor matrix adjustment on and off. This work resulted in the adoption at the time of a standard for NTSC monitors using modern phosphors with a switchable matrix. By the way, the modern phosphors with corrective matrix in the receiver showed the correct flesh tones and red-yellow-green hue range, but produced the expected brightening of reds and darkening of cyans. The work of the committee included selecting the best compromise values for the corrective matrix, to get acceptable hues with "acceptible" brightness changes. There had been a paper published on matrices for color receivers to minimize the squared error for some selection of colors, although I seem to recall it looked only at hue and saturation and ignored brightness.

The precise phosphors adopted were called "SMPTE C." The "C" stood for one of of three formulations that were proposed, and also happened to be those used in Conrac monitors. This batch of phosphors was kept aside and used by whoever supplied CRTs to Conrac and maybe some others. Asian manufacturers were on their own to formulate phosphors that matched SMPTE C.

Later, SMPTE C, EBU and other slight variants were reconciled to the HDTV/sRGB values.
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Old 06-19-2020, 11:10 AM
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Regarding the SMPTE tests: they were set up by NBC/RCA at their test lab in Rockefeller Center. Ask any of the old hands, and they will lament the closing of that lab (long before the GE takeover and RCA's demise) in favor of taking whatever info the camera makers provided. NBC was a stickler on performance of any cameras they purchased, well after RCA got out of the camera business, and could throw their weight around enough to make manufacturers modify their designs if necessary.
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Old 06-20-2020, 02:09 PM
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[QUOTE=old_tv_nut;3224970]

When I was on the NTSC monitor committee at SMPTE, NBC/RCA set up a test with some brightly colored objects, which were displayed on two identical monitors, except that the CRTs had been made by Sylvania with one being essentially SMPTE C and the other having NTSC green. There was a skein of kelly-green yarn that had been found that was specifically outside the modern phosphor range. I do not recall any cyan object that was outside the range. We then compared the two renditions side by side, including turning the monitor matrix adjustment on and off.“

So you saw NTSC green and presumably other NTSC colors on the Sylvania CRT. And no professional camera could capture NTSC colors and now I mean still camera's? Is it possible for you to reproduce as close as possible a 1953 NTSC green color sample based on your knowledge?

I know what your going to say, how can I see it on my monitor. I have DCI-P3 which has 26% wider gamut over sRGB. Not as wide as 1953 NTSC though.

Edit: You said “If you put color bars on your old set, take a picture with a digital camera set to Adobe RGB or prophoto RGB, and display it on a wide-gamut monitor (or the old TV), then you should see the NTSC primaries and secondaries reproduced, sort of.” Would that be reduced luminance/saturation?
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Old 06-20-2020, 05:26 PM
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[QUOTE=etype2;3224992]
Quote:
Originally Posted by old_tv_nut View Post

So you saw NTSC green and presumably other NTSC colors on the Sylvania CRT. And no professional camera could capture NTSC colors and now I mean still camera's? Is it possible for you to reproduce as close as possible a 1953 NTSC green color sample based on your knowledge?

I know what your going to say, how can I see it on my monitor. I have DCI-P3 which has 26% wider gamut over sRGB. Not as wide as 1953 NTSC though.

Edit: You said “If you put color bars on your old set, take a picture with a digital camera set to Adobe RGB or prophoto RGB, and display it on a wide-gamut monitor (or the old TV), then you should see the NTSC primaries and secondaries reproduced, sort of.” Would that be reduced luminance/saturation?
1) Current digital cameras can represent NTSC green in the raw file, or in a jpg file when the camera is set to AdobeRGB color space. Warning: really, you should only use raw files for this, as a jpg file with AdobeRGB is VERY likely to be misinterpreted as sRGB by practially all software out there. Although the camera can REPRESENT NTSC green, whether it will do so exactly if you take a picture of your NTSC CRT is iffy, for several reasons:
1) the spectral responses of the sensor are not linear combinations of the eye cone responses, so saturated colors are distorted to some extent. The good news is that the distortion tends to saturate very saturated colors more than reality, and move them towards the primaries. So, there is a good possibility the green bar will be recorded as fully saturated NTSC green.. Secondary colors (yellow, cyan, magenta) are more likely to give hue shifts.
2) Photographic cameras are not linear photometric/colorimetric devices. The programs that process raw files do not do linear photometric/colorimetric transforms of the raw data. They are trying to make a pretty picture of reality, so you when you take a picture off your NTSC tube, you end up with a picture of a picture, rather than a strict duplicate of what was on the screen.
3) If you have a monitor that reaches NTSC green, and it is properly profiled, Adobe products should do a decent job of showing the result of the camera response and the photographic processing. This should show the more saturated, less yellow green, but whether it will do so precisely is harder to say. For example, in Lightroom, you can choose multiple "camera profiles." None of these are labeled as colorimetric. From the sound of the titles, the closest might be Adobe Neutral, of for a Canon camera, Camera Matching "Faithful." But even these two are different from each other. Each of these profiles affects the hue, saturation, and luminance of the primary and secondary colors differently, not to mention image contrast, highlight and shadow compression, and on and on.

In the end, you have to ask yourself why go to all this effort. You can do it for your own gratification of viewing something on your wide-gamut monitor. You could perhaps share an image (in some format other than jpg) with someone else who has color-managed software and a calibrated and profiled wide-gamut monitor. But if your goal is to show pictures on the web to other TV restorers, the majority won't have all that, so the most reliable thing is still jpg and sRGB. If the viewer only has an sRGB monitor, that's the end of it.

So, yes, you can definitely go in the right direction to take a picture of, and then display, greens closer to NTSC (if your monitor has the capability), but you shouldn't expect precision.
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Old 06-20-2020, 06:57 PM
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“ In the end, you have to ask yourself why go to all this effort. You can do it for your own gratification of viewing something on your wide-gamut monitor. You could perhaps share an image (in some format other than jpg) with someone else who has color-managed software and a calibrated and profiled wide-gamut monitor. But if your goal is to show pictures on the web to other TV restorers, the majority won't have all that, so the most reliable thing is still jpg and sRGB. If the viewer only has an sRGB monitor, that's the end of it.”

Understood. Thank you. I do not have Photoshop or Lightroom. I’ve read about Lightroom. I think we reached a point to invest in these products. I want to experiment more.

Slightly off topic soapbox rant: I’ve spent a reasonable amount of money investing in equipment to get us as close to the “theater experience” as possible. I like movies, the classics and new if properly produced to my liking. So with the high res, WCG, HDR, object based sound equipment in place, Hollywood keeps sending out “color” movies that in my opinion, barely pass as “two color” gamut. There has been a trend over recent years, to bring out overly dark, non saturated color movies and TV shows. You know the ones, I’m talking about. The Producers/Directors say its for the “mood” of the movie. That’s a cop out in my opinion. They talk about the black levels all the time. Maybe if the average Joe (my self :-) ) had a 200K Christie projector we might see and appreciate the content in these recent movies.

I want three strip Technicolor back! They could do it in the 30’s and beyond. Here we are in 2020 watching inferior color. There are exceptions, but far and few between. We seek out the exceptions. We read the history of color movies. First no television, competition from film makers, loss of audience to television, the need to attract folks back to the movies. I guess it all cones down to the $.
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Old 06-20-2020, 08:05 PM
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I agree that the dull cyan and orange look has become an overdone fad. You notice that they don't do green and magenta, as that becomes completely implausible, especially skin tones. So, the restricted gamut is always pushed towards cyan and orange. After a while it's just a boring crutch, substituting for actually thought-out color design.
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Old 06-21-2020, 02:27 AM
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I said it before and say it again... The picture is insignificant compared to the quality of the subject. Both modern television and movies are, for the most part, pure trash. Ever seen pictures of later movies or television audited on televisions here? Damn few if any! Try watching the late '50's and early '60's monochrome westerns on the sub-channels. Wonder why they're still televised?

Movies with heavy CGI are lousy with blue-green scenes. Nothing like the headaches from watching the "Matrix" and "Riddick" movies. Are we too lazy to film properly?
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Old 09-05-2020, 11:39 AM
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The graphics in my paper are adjusted to be correct for an sRGB monitor. The colors on the MacBeth colorchecker chart are within sRGB, except for the cyan, which is only slightly outside. The MacBeth green is nowhere near NTSC green. This illustrates how the NTSC primaries do a very good job of covering the gamut of real surface colors, and sRGB does an adequate job.

When I was on the NTSC monitor committee at SMPTE, NBC/RCA set up a test with some brightly colored objects, which were displayed on two identical monitors, except that the CRTs had been made by Sylvania with one being essentially SMPTE C and the other having NTSC green. There was a skein of kelly-green yarn that had been found that was specifically outside the modern phosphor range. I do not recall any cyan object that was outside the range. We then compared the two renditions side by side, including turning the monitor matrix adjustment on and off. This work resulted in the adoption at the time of a standard for NTSC monitors using modern phosphors with a switchable matrix. By the way, the modern phosphors with corrective matrix in the receiver showed the correct flesh tones and red-yellow-green hue range, but produced the expected brightening of reds and darkening of cyans. The work of the committee included selecting the best compromise values for the corrective matrix, to get acceptable hues with "acceptible" brightness changes. There had been a paper published on matrices for color receivers to minimize the squared error for some selection of colors, although I seem to recall it looked only at hue and saturation and ignored brightness.

The precise phosphors adopted were called "SMPTE C." The "C" stood for one of of three formulations that were proposed, and also happened to be those used in Conrac monitors. This batch of phosphors was kept aside and used by whoever supplied CRTs to Conrac and maybe some others. Asian manufacturers were on their own to formulate phosphors that matched SMPTE C.

Later, SMPTE C, EBU and other slight variants were reconciled to the HDTV/sRGB values.
I went back and read some of your older posts on this complicated subject of NTSC/SMPTE-C matrix variations at the transmitter/camera and receiver, as you seem to be the only source of information on this subject on the internet, ha, but as you've mentioned it here, I thought I'd ask a couple questions as I'm still pretty confused.

I understand, because of the transition in the '60s to using dimmer, less saturated phosphors in monitors and TVs than those specified by the NTSC in 1953, receivers had to adjust Y'IQ decoding (or did they alter R'G'B' values after decoding?) to produce a more palatable image, and cameras made similar adjustments to the linear RGB values before Y'IQ encoding.

In today's world, where we're obviously not receiving NTSC transmissions directly from a TK-41, but at best, watching a VHS or LaserDisc that was probably seen/mastered on a P-22/SMPTE-C phosphor monitor from at least the '80s, is this still relevant? Was this ever an issue with home/consumer video or just with live broadcasts, where encoding for NTSC phosphors was required by the FCC? How can one tell whether their monitor or TV is altering NTSC signals with its own, subjective matrix, or is there even such a thing as unaltered, accurate NTSC in practice? It all just sounds so chaotic, haha.

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Old 09-05-2020, 02:31 PM
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...
I understand, because of the transition in the '60s to using dimmer, less saturated phosphors in monitors and TVs than those specified by the NTSC in 1953, receivers had to adjust Y'IQ decoding (or did they alter R'G'B' values after decoding?) to produce a more palatable image, and cameras made similar adjustments to the linear RGB values before Y'IQ encoding.

In today's world, where we're obviously not receiving NTSC transmissions directly from a TK-41, but at best, watching a VHS or LaserDisc that was probably seen/mastered on a P-22/SMPTE-C phosphor monitor from at least the '80s, is this still relevant? Was this ever an issue with home/consumer video or just with live broadcasts, where encoding for NTSC phosphors was required by the FCC? How can one tell whether their monitor or TV is altering NTSC signals with its own, subjective matrix, or is there even such a thing as unaltered, accurate NTSC in practice? It all just sounds so chaotic, haha.
1) "dimmer, less saturated" is not a good blanket description. Green became yellower. Blue became more violet and saturated. Red became brighter but more orange and less saturated for a few years when sulfide red was used, then was restored to close to NTSC with rare earth reds.

2) Receivers adjusted the R-Y, B-Y, G-Y decoding, but not right away when the phosphors first changed. You can see the difference in successive RCA chassis. Electrical coding of the chroma was always per FCC, even for PAL transmission, which matrixed the R,G,B linear signals differently before gamma correction to R',G',B'.

3)The CTC-100 with 15GP22 is the only set guaranteed to have both NTSC decoding and NTSC phosphors. CTC5 and some successive RCA chassis have NTSC decoding, but the phosphors may differ. 21AXP22 and 21CYP22 CRTS may have NTSC phosphors, but that needs to be measured to verify, because the introduction of sulfide blue is not clearly documented. Sets I saw at the Museum of Science and Industry in the late 50s had suspiciously violet blues and greenish yellows, which you would expect from a more-violet blue phosphor combined with NTSC decoding.

4) Yes it was very chaotic

5) I suspect that re-issued LIVE programs shot with TK-41 image orthicon cameras, such as the Dean Martin show, may not have been rematrixed in any way, and only had the chroma amplitude and phase adjusted.
Assuming no rematrixing:
The adjustments may have been made looking at a later non-NTSC monitor, but if there was no re-matrixing, receiver controls on a CT-100 could easily reverse any error. Later sets of the same vintage as the program or earlier will accurately reflect what those sets would have shown at the time.

6) Re-issued film programs, like Bonanza, that have been rescanned on later gear, are completely suspect as to whether they show the same color as the original broadcasts on the sets of the time. Subjectively, the color is probably much better because the newer scanners are much improved over the old Vidicon chains in terms of shading and color distortions caused by the Vidicon's nonlinearity.
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Old 09-05-2020, 03:17 PM
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1) "dimmer, less saturated" is not a good blanket description. Green became yellower. Blue became more violet and saturated. Red became brighter but more orange and less saturated for a few years when sulfide red was used, then was restored to close to NTSC with rare earth reds.

2) Receivers adjusted the R-Y, B-Y, G-Y decoding, but not right away when the phosphors first changed. You can see the difference in successive RCA chassis. Electrical coding of the chroma was always per FCC, even for PAL transmission, which matrixed the R,G,B linear signals differently before gamma correction to R',G',B'.

3)The CTC-100 with 15GP22 is the only set guaranteed to have both NTSC decoding and NTSC phosphors. CTC5 and some successive RCA chassis have NTSC coding, but the phosphors may differ. 21AXP22 and 21CYP22 CRTS may have NTSC phosphors, but that needs to be measured to verify, because the introduction of sulfide blue is not clearly documented. Sets I saw at the Museum of Science and Industry in the late 50s had suspiciously violet blues and greenish yellows, which you would expect from a more-violet blue phosphor combined with NTSC decoding.

4) Yes it was very chaotic

5) I suspect that re-issued LIVE programs shot with TK-41 image orthicon cameras, such as the Dean Martin show, may not have been rematrixed in any way, and only had the chroma amplitude and phase adjusted.
Assuming no rematrixing:
The adjustments may have been made looking at a later non-NTSC monitor, but if there was no re-matrixing, receiver controls on a CT-100 could easily reverse any error. Later sets of the same vintage as the program or earlier will accurately reflect what those sets would have shown at the time.

6) Re-issued film programs, like Bonanza, that have been rescanned on later gear, are completely suspect as to whether they show the same color as the original broadcasts on the sets of the time. Subjectively, the color is probably much better because the newer scanners are much improved over the old Vidicon chains in terms of shading and color distortions caused by the Vidicon's nonlinearity.
Thanks for the reply.

I think you may have answered this in your third point, but did receivers *always* adjust decoding of NTSC signals for newer phosphors after the '60s, even in the '90s or '00s, or was it ever designed out of the standard, i.e. encoding directly for SMPTE-C, receivers decoding without assuming 1953 NTSC? It seems nonsensical that they would continue encoding for, really, a dead standard decades after the last full NTSC sets were produced, but then if they did alter the target, that would probably wreak havoc with receivers that adjusted decoding.

Also, is "R-Y, B-Y, G-Y" just the decoded R'G'B' in the receiver?

Last edited by pidade; 09-05-2020 at 03:20 PM.
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