#1
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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 |
#2
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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. |
#3
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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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____________________________ ........RGBRGBRGB ...colour my world |
#4
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NTSC+VIR gave superior picture to PAL - none of the drawbacks.
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#5
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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 LFOD ! |
Audiokarma |
#6
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...
Last edited by andy; 11-18-2021 at 04:51 PM. |
#7
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Quote:
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. |
#8
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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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"When resistors increase in value, they're worthless" -Dave G |
#9
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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. |
#10
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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! |
Audiokarma |
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