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  #1  
Old 11-06-2018, 03:37 PM
kfbkfb kfbkfb is offline
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Total Automatic Color - 1969

Might be a little OT:

Magnavox marketed their Total Automatic Color
("automatic" Tint/Hue and Color control system)
starting in 1969.

Other TV makers followed with similar systems.

I think it'd be interesting to create images representing
how these auto tint/color systems actually distorted
the pictures, all the while making the pictures more
appealing to the average viewer.

IIRC, the Magnavox system had 2 settings (I guess if
the local station had sloppy engineering, the more
extreme setting could be used).

Kirk Bayne
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  #2  
Old 11-06-2018, 05:05 PM
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I don't think this is off-topic, although it's been discussed on VideoKarma before (and also has some relation to video color encoding, because, after all, they both affect the result).

The most often used technique (and used by Magnavox even before "TAC") was to spread the demodulation angles between R-Y and B-Y. This had the equivalent effect of reducing Q axis (green-purple) gain (color saturation). Early Maggies also had a switch that set the crt tracking to sepia tones (the tradename escapes me). Both of these changes moved colors on the orange side of the circle toward flesh tone. Sets that did this very strongly gave rise to "the tan cowboy on the brown horse riding into the orange sunset" look.

RCA had a unique hue correction system that actually worked on the phase of the reference subcarrier. It moved hues that were close to flesh hue even closer, without affecting the amplitude or phase of greens, blues, or purples.

Some Motorola tube sets with the single-tube chroma oscillator/demod had three color controls - the usual hue and saturation, plus a red/blue balance. This third control affected the color tracking towards either sepia or blue. It was actually needed for accurate tracking, as the demod outputs were DC coupled to the crt grids, but in the cheaper models, fixed resistors were used and the third control was eliminated. This single tube chroma circuit also had week greens to begin with, as they were taken off the cathode of the single demod tube and were too low in amplitude and not quite the right phase for correct color. So, that helped eliminate greenish flesh tones.

Trade names like "TAC" or "Instamatic" often arrived with solid state sets that had a single button to actuate the color "correction" along with AFC and preset hue and saturation controls, plus often some sort of automatic saturation adjustment, and sometimes a light sensor to adjust contrast and brightness according to room lighting.

RCA used an average chroma signal sensing adjustment. I hated it, but consumers seemed to prefer it, even though it could produce some over-saturated "calendar art" results if the customer preference was set too high, and on the other hand could have noticeable fading of color due to bright red clothing if the preference was set lower. Zenith used a peak chroma compression that prevented reds from blooming if the chroma in a transmission was too high. It could still result in noticeable errors such as oversaturated skin tones, especially if the preference controls were set wrong, but on the other hand did not have the saturation "breathing" with content change that the RCA sets could present.

Much of the need for "automatic color" went away gradually as the TV manufacturers and broadcasters cooperated on controlling variations in transmission, but analog cable systems introduced hue, saturation, and black level errors all over again, as they had many more proc amps to manage in their systems.
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Old 11-06-2018, 05:18 PM
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Of course this is the whole point of PAL and Secam ... would CPA have avoided successfully phase error???

Phase error in PAL theoretically result sin slight reduction in chroma saturation ... but in the 30 years of analog broadcasting here in Australia I was never aware of the deficiencies of PAL ... and never had any phase errors apparent.
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Old 11-07-2018, 07:49 AM
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Quote:
Originally Posted by ceebee23 View Post
PAL [D].. results in .. reduction in .. saturation ..
NTSC+VIR gave superior picture to PAL - none of the drawbacks.
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Old 11-07-2018, 08:09 AM
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We called Maggys switch the "brownilator" switch. IIRC
TAC came later in the early solid state years. Everybody had a
auto color switch & plugged it. I dont think any did any good,
I always watched with it off. Old TV Nut summed it up well.
IMHO the only "auto color" that worked was VIR. Used first in
top line GE's ( of all people ! ) then Panasonic had some.

https://ieeexplore.ieee.org/document/4043073

Maggy gets credit for one huge step, the intro of comb filters.
When that came out people would ask "why is that so much better
picture ?" It stepped most up to the top of line sets easily where
we had a better margin.

73 Zeno
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Old 11-07-2018, 10:36 AM
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I've never cared for any of the numerous auto color, or other picture enhancement features that have come and gone over the years. I always turn them off. On Sony sets from the 70's that have a single button for AFT and auto color, I disable the auto color part so I can still use the AFT. I find that their auto color always results in excessive saturation. VIR was a good idea, but it was never well implemented. Fortunately, modern broadcasts and signal sources are stable enough not to need constant adjustment of the set's controls.

The is off topic, but this extends even to modern flat panels. Turning off all of the image enhancement features invariably results in a better picture. They just try to make the picture look different so it stands out in the store. That usually means more (too much) of everything. The worst offenders are frame interpolation, sharpness enhancement, and noise reduction. Combine those with the default saturation and contrast settings (which are always too high) and everything looks like a cartoon.
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Old 11-07-2018, 01:11 PM
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Quote:
Originally Posted by zeno View Post
IMHO the only "auto color" that worked was VIR. Used first in
top line GE's ( of all people ! ) then Panasonic had some.
We had one of the first GE sets when I was a kid. The station never got it set right so when it was activated you'd get bright blue faces, etc. We just turned it off after a few days.

Quasar also sold some VIR sets in that era, probably around 1979-1980. I worked in a shop that sold and serviced Quasar sets and one year on family vacation I pestered my dad to drop by the Quasar factory in Franklin Park since we had to pass through Chicago anyway. Somehow (I'll always love my dad for this), he got off the highway, went to a pay phone, called up the factory and explained that he had a 15-year-old son in the car who wouldn't shut up about Quasars. Eventually he got connected to...someone in a suit who said sure, come on by. So that morning my precocious 15-year-old self and my extremely bored family got to spend an hour or so touring the assembly line, watching workers stick components in DynaModules as they headed for a wave-soldering line, and pestering the guy in the suit with awkward questions about whether the new DynaColor with VIR could correct a bad color signal from the station, and why Audio Spectrum Sound didn't sound any better than the regular speakers.

Anyway. Quasar had VIR for a year or two.
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Old 11-07-2018, 04:48 PM
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"Philcomatic" and Zenith's "chromatic" and RCA's ACM just seemed to switch in a second set of preset color pots. Great if you cant adjust color, you can return to "factory settings" despite the fact your set is aging and they wont be spot-on for long.

I think Magnavox used the "chromatone" switch as a selling feature in 1965-68 when many monochrome programs were still being broadcast. Maybe gray scale was harder on the eyes than a brown-red sepia tone.
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Old 11-08-2018, 11:28 AM
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Right from the start, the PAL system had to be hacked by adding an expensive delay-line that introduced more problems:
It cut chroma resolution and messed with saturation. Only NTSC/VIR could offer true original-reference saturation.
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Old 11-08-2018, 08:20 PM
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My '65 Magnavox had large wide deluxe stereo cabinet with 12" woofers oriented outward and exponential horn speakers firing at 45 deg angles - inspired by JBL 'Paragon'?

It had a 23" rounded corner picture tube with green tinted escutcheon (like roundies) to make picture seem larger. It featured auto-color that could be selected with a slide-switch, along with thumbwheel controls (along upper back of TV) that allowed presets, that could be locked in with second slide-switch. Its chromatic signature - phosphors & matrixing - gave the picture a felicitous, warm red/yellow character.

It said made in Indianapolis. Their manufacturing plant must have had a rail siding like Zenith's Chicago plant to ship the big consoles cheaply! Maybe the same facility Philips later took over with the buyout? Philips wanting to really learn the meaning of pain competing directly with the Japanese!
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