Here we go.
More stuff about the beginnings of color TV.
We’re continuing from the last video so click up above if you got here somehow without
seeing those or find the link down in the description.
I’m back in a long sleeve shirt cause I’m about to go to work, so let’s get cracking.
NTSC often received the nickname “Never The Same Color” or similar due to its reliance
on the phase offset alone to determine hue.
Unless the television set was dead on the money with the way it handled the color burst,
it would be very likely that it decoded the chroma data slightly out of phase and the
color would be messed up.
The tint control on a television would allow for manually shifting the reference point
from the color burst to correct for errors, with incorrect skin tone usually being how
one identified a problem.
After vacuum tube circuitry was replaced with transistorized equivalents, most of these
problems went away, and automatic tint control eventually became standard on television sets.
By the mid 1970’s, broadcast equipment had progressed to the point that the color burst
was always transmitted with the exactly correct phase, pretty much removing the need for tint
control altogether.
PAL, the standard in most of Europe, reversed the phase of the color encoding on each alternate
scan line, hence its name Phase Alternating Line.
This made it such that a tint control was not needed as the television would automatically
find the correct phase offset through averaging the alternate lines, and thus PAL was generally
deemed superior.
Europe received color television more than a decade after the US, in part because of
the more challenging geography of Europe.
The NTSC system would drift color badly if transmission conditions weren’t more or
less ideal.
So Europe waited patiently for a better system, which PAL most certainly is.
Telefunken in Germany patented PAL, the work of Walter Bruch, in 1962.
The first broadcasts of this new system occurred in 1967 on BBC 2 in the UK.
Apparently this was of the Wimbledon Championships and let me just say that as an American, my
reaction to learning this fact was “Of course it was Wimbledon”.
ON THAT NOTE, I was rather annoyed by this sort of comment.
And I’ll tell you why.
Just pause for a minute as ask yourself, was NTSC a choice?
How could it have been a mistake?
It was the first broadcast black-and-white compatible color television transmission scheme
on the planet.
PAL is virtually identical to NTSC with the exception of the alternating phase.
Of course it would be better, it was developed later, specifically to address NTSC’s weaknesses.
We were stuck with it in the States because it was already there, and we weren’t about
to pull the plug on an existing standard.
That’s the whole reason we spent so much time making color TV compatible with black
and white sets.
I think many people appreciate PAL’s much higher image resolution of 625 lines verses
525 in the US, but that extra resolution came at the expense of a reduced frame rate.
And speaking of framerates,
One commenter on the last video was singing the praises of PAL because, with a framerate
of 25 FPS, movies running at 24 frames per second just need to be sped up by 4% to be
converted to a PAL broadcast.
I’m sorry, but I completely disagree with that being “better”.
I don’t want to just speed up the film!
We used Three-Two pull down, which sort of blended frames together by advancing the film
frame between television fields.
In effect some film frames were shown over two fields, and some three.
Most people, in fact I’d say virtually all people, can’t see this, since the fields
aren’t drawn together.
And since it leaves the runtime and audio as they should be within .1%, I’d much rather
do that!
And speaking of speaking of framerates, lets discuss the 29.97 frames per second nonsense
brought to you by NTSC.
Matt Parker of Standup Maths made a video about this very thing, which I shall link
to now.
Simply put, the carrier frequency of the audio signal could interfere with the chrominance
carrier and produce a visible dot pattern on the screen.
To keep this from happening, the audio carrier frequency needed to be an integer multiple
of the line rate.
Which it wasn’t.
So, something had to give.
You couldn’t just change the audio carrier, though, cause that would mess up existing
TVs.
But you could change the line rate, or frequency.
By reducing the line frequency from 15,750 Hz to 15,734 Hz the audio carrier was now
exactly 286 times the frequency of the line rate, rather than some nasty number.
This would minimize interference and prevent the dot pattern from occurring, and existing
television sets wouldn’t be bothered by the change as their vertical hold circuitry
was designed to compensate for slop in the vertical retrace frequency.
Of course, lowering the linerate lowered the frame rate, as it’s still 525 lines per
frame, so the frame rate was lowered to 29.97 frames per second entirely as a side-effect
of compatible color.
In PAL countries, this wasn’t ever an issue.
It turns out backward compatibility wasn’t ever on anyone’s mind in europe, or at least
those disinterested in it won out.
For example, in the UK, BBC2 started black and white 625 line broadcasts in 1964, and
owners of older 405 line televisions just wouldn’t get to see it.
This was about 10 years after NTSC had started broadcasting.
And PAL was based on the 625 line standard, and likely due to the known framerate debacle,
the audio carrier in this standard was specified to be an integer multiple of the linerate,
15,625 hertz.
Thus the frame rate could stay an even 25 frames per second once color broadcasts began
without the audio carrier affecting the image.
In the previous video, I said that because the chrominance carrier is suppressed during
transmission, most of the interference between chrominance and luminance is eliminated.
But not all of it is.
Black and white televisions made after the changeover to color were designed to filter
out this interference, but earlier televisions or cheaper ones without the filter circuit
would display a pattern of dots in highly colored areas of the screen.
The dots were a visible manifestation of the chrominance carrier’s interference.
Now, I’m going to make a speculative statement because I couldn’t find anything to confirm
or deny this after hours of poking about online, so here goes.
Because the luminance signal is used in calculating I and Q, it seems to me that the luminance
signal itself must be manipulated at precise times to actually create changes in the calculated
I and Q values, otherwise it would seem their calculated output would always be the same
for a given brightness.
I believe that the chroma dots are the visual manifestations of this happening.
I have read that the dots are most visible in highly colored areas, which makes sense
as the amplitude of the chroma carrier dictates the saturation of a color, and the phase difference
the hue.
It therefore sounds to me like the Y carrier is constantly being altered along with color
information, and that alteration appears as dots.
If that’s not at all why the dots appear please comment below.
ANYWAY, the dots would turn out to be useful in the 21st century.
Many older television programs were recorded onto videotape masters that were re-used to
lower production costs.
With these master tapes lost, the only copy of the TV shows that remained were on film,
transferred via telecine.
In many if not most cases, this film was black and white.
This had led to many of these early color television shows only being preserved in black
and white.
But some TV studios used a telecine to capture the output from a black and white monitor
that didn’t filter out the chroma dots.
Using modern software, these dots have been used to reconstruct the color.
By carefully examining the magnitude and position of these dots, the color information can be
extracted.
This wasn’t an easy task, mind you, particularly with the extra geometry component added by
the curved glass screens of the monitors, but it’s still an amazing thing.
I’ll link to some more info down below if you’d like to learn more.
Now let’s talk a bit more about Guillermo Gonzalez Camarena.
Two videos ago I briefly talked about him and his clever but ultimately inadequate color
wheel adapter for black and white televisions.
He’s also known for inventing a CRT with two electron guns rather than three.
This would supposedly make color televisions cheaper to produce.
However, there are two glaring problems with attributing him to “inventing” that.
First, if there were an individual who were to have experimented in two color TV long
before Gonzalez Camarena, who would you guess that to be?
Anyone?
I’ll give you a hint, he’s Scottish!
That’s right, it’s JOHN LOGIE BAIRD.
He’s a persistent little bugger, isn’t he?
Now I’m starting to see why people feel so strongly about his contributions to television.
So first, two-color “color” can be achieved using complementary colors.
In fact, the first Technicolor films were done with a red and green film strip all the
way back in 1916.
Baird used a really wonky looking picture tube called a Telechrome which instead used
cyan and red-orange phosphors.
These two colors can produce a realistic skin tone and a limited range of other colors.
He came upon the concept for the telechrome in 1942 and demonstrated it in 1944.
Gonzalez Camarena’s idea is dated to 1963, with one source saying 1962.
Links are below.
But a far more damning issue against Gonzales Camarena is the fact the the 1953 NTSC standard
includes support for two color receivers!
That’s right, that whole I and Q business?
It turns out, I on its own is a two color gamut.
A television could be built with cyan and red-orange phosphors and demodulate only the
I signal, and you would get a functional two color TV.
This may also help to explain why I is given three times the bandwidth of Q.
If it were meant to be able to produce a reasonable color image on its own, it would make sense
to prioritize bandwidth to I over Q.
But the fact of the matter is, two color “color” is never as good as three color.
Skin tone might look right, but not much else will.
Thus, since you’d need almost the same amount of manufacturing complexity to produce a two
color CRT as a three color--still need a shadow mask and phosphor grid, you’re really just
losing one electron gun--it was never deemed to be worth the significantly worse color
fidelity in exchange for a few pennies saved.
Many people correctly commented in previous videos that the color wheel from the CBS system
survived in single chip DLP projectors and televisions.
But you might not have known that for a brief time in the 1950s, you could purchase a kit,
called the Col-R-Tel, to convert your existing black and white TV into color.
By performing a few wiring modifications, you could add a device which would extract
the color data from an NTSC broadcast, alter the CRT’s output to a sequential field system,
and use a color wheel to reproduce the color sequentially.
Gonzalez Camerena’s work would actually be a thing after all.
There’s a great link down below, along with many many others, if you’d like to learn
more.
And for my last tid-bit, a brief word on shadow masks, aperture grilles, and Trinitron.
I’m still planning on making a separate video showcasing Trinitron, but some people
have correctly pointed out that the CRT set I’ve been using for demonstrations doesn’t
have the same type of shadow mask that CRTs of the time did.
I do have a device which has the original type CRT, but it doesn’t really fit well
into this discussion.
Well, here, I’ll show you.
♫ Macintosh Startup Chime ♫
Yep. That’s it.
Doesn’t really fit into the video, now does it?
Most CRT computer monitors--if not all that aren’t Trinitron--use a design similar to
what you’d find on the earlier color sets.
These CRTs don’t have the individual triads like you see here, instead it’s just a repeating
pattern of red, green, and blue circles.
Because of the high image resolution needed in a computer monitor, a very fine dot pitch,
the term used to describe how many dots appear over a given length, was required.
The CRT from the GE set uses a more modern phosphor and shadow mask design which increases
the phosphor-to-mask ratio, but at the expense of a coarser dot pitch.
This design was used in televisions to better compete with Trinitron displays.
But again, we’ll talk more about that later.
As always, thank you so much for watching!
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And, I’ll see you next time.
(Exasperated) Wooh!
Hoh, OK