The year is 1954.
After much deliberation, confusion, and fussing
about, the FCC had, for the second time, settled
on the way color TV would be transmitted in
the United States, and Westinghouse would
release the first commercially produced color
television set using the new standard, the
Westinghouse H840CK15.
Ah, the H840CK15.
Really rolls off the tongue.
RCA would follow with the more famous CT-100
weeks later.
The reason for the fussing about had to do
with compatibility.
Most experimental color televisions used complicated
schemes to create a color image which would
not be compatible with existing black and
white televisions sets.
It seemed like this was an inevitability,
and the FCC did briefly approve simultaneous
transmission of both color and black and white
signals, creating a fragmented television
landscape.
But the National Television System Committee,
NTSC, having backed the work of RCA, would
save the day by introducing a new color system.
Their compatible color managed to, in a sense,
hide the color signal within the black-and-white
transmission.
The benefits of a single transmission for
both color and black and white television
sets were obvious, and though it took some
convincing, the FCC would later decide that
new NTSC color was the way to go.
To understand this story, we need to look
at how color images are made.
Our eyes actually only see three colors of
light--Red, green, and blue.
Our brains interpret other colors by comparing
the amount of each of the three colors we
see, for example yellow light will stimulate
both the red and green cells in your eyes
in close to equal amounts as yellow lies between
green and red on the color spectrum.
We knew this for a long time before television
was around, in fact this knowledge can be
traced back to 1802 with Thomas Young’s
pretty correct postulation.
This was further refined in 1850 by Hermann
von Helmholtz and thenceforth was known as
the Young-Helmholtz theory.
Experiments in color photography were done
almost as soon as we figured out photography,
and the three-color method, as suggested by
Scottish physicist James Clerk Maxwell based
on the Young-Helmholtz theory, worked perfectly.
Plenty of very old color photographs exist,
and this one is perhaps my favorite.
The only clue that this photograph is from
1912 is the moustache.
Anyway, with humans possessing the knowledge
of how to recreate an image in color using
an RGB system, it should be no surprise that
we threw our hats into the ring for color
television as soon as we figured out television.
The first color television demonstration was
done by none other than our friend John Logie
Baird,
who adapted his mechanical television system
to produce color all the way back in 1928.
But as we know, mechanical television was
not meant for this world.
CRT based electronic television was far superior.
So, we got to work figuring on out how to
adapt a CRT into a color display.
The most obvious thing would be to simultaneously
transmit three separate television images,
with each representing one of the RGB channels.
A special camera with a beam-splitting arrangement
behind the lens could send the image to three
separate iconoscope tubes, each with a colored
filter in front of it.
Later cameras would use dichroic glass to
simultaneously split the beam and filter color.
This would cause each tube to only detect
light of that color.
On the receiving end, three separate television
picture tubes could receive each of these
three signals.
RCA experimented with just such a system.
The three CRT displays were tinted either
red, green, or blue, to match the colors detected
by the tubes in the camera.
The trick was combining the images together.
An optical system similar to that of the camera
could re-combine the output of the three CRTs,
but this didn’t work too well.
Though CRT projection systems would use this
approach years later, at the time it wasn’t
a great option.
Besides the fact that each television set
using this system would cost at least three
times as much as an ordinary television, given
the fact it essentially is three TVs, the
resulting image had to be recombined onto
a frosted screen, and with the comparatively
dim tubes of the time, it just wasn’t great.
The real trick would be to figure out how
to use just one picture tube.
Once again, John Logie Baird appeared.
In 1940, he demonstrated a sequential color
system using CRT technology.
But, I’ve also found a source indicating
this was in 1939.
Also in 1940, CBS demonstrated their sequential
color system.
Regardless of who was first, both of these
systems are similar.
These work by placing a large disk in front
of a black and white picture tube.
This disc contained alternating sections tinted
red, green, and blue.
This disc was quite a bit larger than the
tube, so that only one color was in front
of the tube at one time.
The disc would tint the apparent color of
the picture tube, and by spinning the disc
quickly in front of it, it would rapidly produce
a red, then green, then blue image.
If you do this fast enough, persistence of
vision will kick in, and you won’t notice it.
A similar disc was placed in front of the
camera tube in the studio, so that it would
only see red, then green, the blue light.
So long as you can synchronize the camera
and TV, you could transmit a full color image.
But now is where we run into problems of compatibility.
You could in theory just slap one of these
discs in front of both a conventional camera
and conventional TV, and it would work, but
it would be painful to view.
With a framerate of 30 frames per second,
each color would only appear in front of the
tube 10 times per second.
This would be obvious.
In fact, avert your eyes if you suffer from
epilepsy, it would look like this.
This isn’t great, now is it?
Even if you spun the disc twice as fast and
tinted each consecutive field and not frame,
it would still be very visible.
And now,
I was pleasantly surprised to learn of Guillermo
González Camarena, a Mexican inventor who
applied for a patent detailing a system much
like we’ve just discussed in 1940.
Thanks to multiple commenters for letting
me know about him.
Information about him is very spotty.
For example, there is a Wikipedia entry on
him, but it’s pretty paltry and also somewhat
contradicts itself.
The actual patent is easily accessible, though,
and it’s worth taking a look at.
We’ll explore Camarena’s work in more
detail in the next video, including his work
on two-color TV, but first I need to address
a small issue.
His patent was to adapt an existing black-and-white
set to color.
This wouldn’t look too good, as we just discussed, as the color wouldn’t change fast enough.
It would technically work, but its practical
viewability would be questionable.
He had the idea fundamentally correct, but
the CBS system produced far and away better
results.
Also, CBS’s demonstration to the press of
their field-sequential color-system happened
just 9 days after Guillermo filed his patent.
So here we are again, with multiple people
who could be given credit as the inventor
of color TV.
So we’ll just say it was a group effort.
CBS actually brought their system to commercial
use.
However, the CBS system radically altered
the way television transmissions were done.
To get around the high flicker caused by the
color wheel, they elected to increase the
field rate from 60 hz to 144 hz, but in order
for each two-field frame to be completely
colored, the wheel needed to cycle through
the RGB pattern twice with each frame, reducing
the effective frame rate to 24 frames per
second.
This was very effective at making the color
wheel hard to notice since it changed colors
144 times per second, but it came at the huge
expense of wiping out any compatibility with
existing black and white televisions.
But, the color wheel was simple.
Aside from the extra circuitry required to
synchronize the wheel with the correct fields,
it was really a run-of-the-mill black and
white TV and camera, both modified with a
much higher scan frequency, and with a spinning
color wheel in front of each of them.
It was easy to produce and worked reasonably
well, and so the FCC decided they would allow
broadcasting of the CBS color system.
On June 25th, 1951, the first network color
television broadcast occurred.
But this whole time, RCA was trying to convince
the FCC of their “compatible color” system.
They understood that if would be really great
if you could broadcast a color transmission
that could still be viewed with the black
and white televisions already in service.
And to make that possible, they needed a whole
new type of picture tube.
Enter the shadow mask.
One simple way to make a color picture tube
would be to create a pattern of alternating
red, green, and blue dots on the inside surface.
From far enough away these dots would blend
into each other and wouldn’t be noticeable.
So, RCA used picture tubes which contained
just an arrangement, with each dot being filled
with either a red, green, or blue phosphor.
This tube could be scanned at the same field
and frame rate as an ordinary black and white
tube, but could produce a full color image.
But now you need a way to control which dots
are lit up.
If they all worked together, it would simply
appear as black and white.
You need a way to control where the electron
beam lands.
The shadow mask is just the solution.
The 1938 invention of German man Werner Flechsig
is a sheet of metal with a bunch of tiny holes
punched through it.
The shadow mask sits just behind the grid
of phosphors.
The holes work in conjunction with three separate
electron guns, one for each color of phosphor,
in the neck of the picture tube.
These guns are arranged in a triangular pattern,
and their beams converge right at the shadow
mask.
The mask prevents the beams from landing on
the wrong color, as the beam can only pass
through the mask at a certain angle, thus
ensuring there’s no accidental cross-over.
This is why placing a magnet near the face
of a color CRT makes such far-out patterns
appear.
The magnet bends the beam after the shadow mask, and thus the electron beams land where they shouldn't.
Now comes the time to explain the thumbnail
of this video.
It’s very important to understand that the
individual groupings of red, green, and blue
phosphors are NOT pixels.
The TV set isn’t even trying to line the
beam up with these triads, if you will, and
it has no way to address them individually.
In fact, the pattern of triads in this picture
tube doesn’t even form a grid, as each adjacent
column of triads is shifted up half way.
But that makes sense when you keep in mind
that the electron guns are arranged in a triangle--logically
the targets they aim to hit would be, too.
And before you bring up Trinitron, I’ll
be addressing that in another video.
Hold your commenting horses.
To form an image, the face of the tube is
scanned in horizontal lines just like a black
and white television set.
It’s these lines that make up the image,
not the dots on the screen.
This is the precise reason why I used a black and white TV in my video on how analog television works.
The lines are obvious on a black and white
set, but a color set makes them less so.
It’s tempting to imagine these groupings
as pixels, but in reality they are simply
a regular pattern of dots which, when combined
with the shadow mask, force each individual
electron beam into its respective color.
This is most easily demonstrated with white
text on a black background, so let’s pull
out the old PlayStation.
The text here doesn’t fall nicely in line
with the individual phosphor groupings.
All around the edges of the text, the phosphor
groupings are only partially lit.
That’s because the scan line isn’t landing
nicely within the center of the triads, and
it just barely grazes the bottom of these
triads.
But it doesn’t matter, as the position of
the shadow mask and phosphor triads is irrelevant
to the scanning beam--the beam can land anywhere
it wants.
But the shadow mask will always prevent each
individual color component of the beam from
hitting the incorrect phosphor.
The shadow mask worked really well, but it
required very powerful electron beams.
About 85 percent of the beam energy is lost
just in the shadow mask, so only 15 percent
gets through the tiny holes.
Without really powerful electron guns, a dim
image would result.
Even with suitable electron guns, early color
CRT displays were often less bright than their
black and white counterparts.
Nevertheless, it meant that the picture tube
could on its own produce a full color image.
The real challenge then was to find a way
to transmit color television in a way that
a color set could interpret but that would
still work for existing black and white TVs.
You could simultaneously transmit three separate
monochrome images and assign one to the green
electron gun, another to the red, and the
final to the blue.
But which one would you have the black and
white television receive?
Picking just one color would produce a very
unnatural image on the black and white set.
Also, this would triple the bandwidth needed,
which wasn’t really gonna fly with the FCC.
Stay tuned as in the next video, we’ll explore
how RCA managed the seemingly impossible task
of sending three times the data without needing more bandwidth--by hiding the color in plain sight.
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you enjoyed the video!
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