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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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16th Nov 2017, 1:56 pm | #21 |
Dekatron
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Re: Colour Wheels etc.
Last edited by peter_scott; 16th Nov 2017 at 2:02 pm. |
16th Nov 2017, 2:05 pm | #22 |
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Re: Colour Wheels etc.
Marconi's 1954 public demonstration of 405 line NTSC TV included both RCA tri-colour tubes and three-tube projection tubes, the latter using modified Philips-Schmidt projector tubes: see pages 12 and 15 of the Marconi booklet here:
http://www.earlytelevision.org/pdf/M...and-slides.pdf Unfortunately no illustrations or details of the three tube apparatus are given. |
16th Nov 2017, 2:12 pm | #23 |
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Re: Colour Wheels etc.
I took a picture of such a device when I was at ETF.
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16th Nov 2017, 2:23 pm | #24 |
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Re: Colour Wheels etc.
I had assumed that the Marconi three tube apparatus would have been in a self-contained cabinet: the picture size was only 9" x 12" like some contemporaneous black and white projection TVs, but I suppose that would have required a beam splitter arrangement to ensure that the RGB images were in register.
Some time in I think the 1970's I recall reading in a photographic magazine that the only place you could get prints made directly from the original three-strip Technicolor negatives was China, most of the cameras, and all the processors, together with know-how, having been sold to the Chinese for use by their then-expanding film industry. A couple of years ago a poster on this forum observed that many modern film makers were having Technicolour-like RGB three-strip separation negatives made on conventional black and white film stock for future-proofed archiving purposes. The silver content of a B./W negative does not change with time, and it is easy to reproduce pure red green and blue filters to make projection prints, although nowadays the negatives would normally be used to make electronic copies. Last edited by emeritus; 16th Nov 2017 at 2:38 pm. |
16th Nov 2017, 5:11 pm | #25 |
Heptode
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Re: Colour Wheels etc.
Interesting that there were 'flirting' with offset I&Q axis as per NTSC, together with a modest pedestal. I suppose they had no reason to think differently at the time.
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16th Nov 2017, 9:38 pm | #26 | |
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Re: Colour Wheels etc.
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16th Nov 2017, 10:21 pm | #27 |
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Re: Colour Wheels etc.
This one?
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16th Nov 2017, 10:21 pm | #28 |
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Re: Colour Wheels etc.
As proven by J.L.Baird a colour TV system can be realised by using cyan and magenta.
A two carrier system which is not compatible with ordinary monochrome TV therefore unsuitable for normal broadcasting systems. DFWB. |
16th Nov 2017, 10:32 pm | #29 | |
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Re: Change your B/W TV into colour?
Quote:
https://youtu.be/i2aroixiuTc |
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16th Nov 2017, 11:03 pm | #30 |
Hexode
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Re: Colour Wheels etc.
I have memories of an article in "Television" in the early 1970's describing a mechanical triple sequential switch called the TRITCH to switch the "colour" images to the CRT, and to synchronise the filter disc.
Kevin |
16th Nov 2017, 11:32 pm | #31 |
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Re: Colour Wheels etc.
Info on the Tritch from ETF:
http://www.earlytelevision.org/pdf/c...tor_manual.pdf Also: http://www.earlytelevision.org/colordaptor.html Peter Last edited by peter_scott; 16th Nov 2017 at 11:40 pm. |
17th Nov 2017, 6:05 am | #32 |
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Re: Colour Wheels etc.
I have a book called something like 'Physical Science -- Man's Conquest of Matter and Space' which shows diagrams of some rather odd colour CRTs.
The simpler has a glass plate inside the envelope. One side of the plate is coated with red phosphor, the other with blue-green phosphor. The envelope is shaped rather like that of an iconoscope but with 2 necks, each containing an electron gun. One points fowwards (and down), the other backwards, and each electron beam scans the phosphor on one side of the glass plate. You viewed the pictur on the plate through the glass envelope, the picture did not appear on a screen that was part of the envelope as with most CRTs. The other had a similar glass plate with 'triangular wave' ridges on one side. The flat side of the plate was coated with red phosphor, the top edge of each ridge with green and the bottom edge with blue. Similar envelope with 3 necks and 3 electron guns. You guessed how it worked.. I have never seen such devices in any other book though. |
17th Nov 2017, 10:05 am | #33 |
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Re: Colour Wheels etc.
Hi Tony,
That sounds a bit like Baird's Telechrome. See: http://www.earlytelevision.org/baird...nic_color.html Peter |
17th Nov 2017, 10:34 am | #34 |
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Re: Colour Wheels etc.
Wasn't the colour camera flown on the Apollo programme a colour wheel type, by RCA if I remember?
David
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17th Nov 2017, 11:43 am | #35 |
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Re: Colour Wheels etc.
Hi David,
Apollo 8 used an RCA Field Sequential Camera. Apollo 9 used Westinghouse. Quoted from Wiki. "Lebar and his Westinghouse team wanted to add color to their camera as early as 1967, and they knew that the CBS system would likely be the best system to study.[36] The Westinghouse Lunar Color Camera used a modified version of CBS's field-sequential color system.[35] A color wheel, with six filter segments, was placed behind the lens mount. It rotated at 9.99 revolutions per second, producing a scan rate of 59.94 fields per second, the same as NTSC video. Synchronization between the color wheel and pickup tube's scan rate was provided by a magnet on the wheel, which controlled the sync pulse generator that governed the tube's timing." Apparently they didn't use colour wheels at the receiving end. Peter Last edited by peter_scott; 17th Nov 2017 at 12:04 pm. |
17th Nov 2017, 11:58 am | #36 |
Hexode
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Re: Colour Wheels etc.
The colour cameras used on the Apollo missions were definitely the field sequential type using a colour wheel. Ross
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17th Nov 2017, 12:31 pm | #37 |
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Re: Colour Wheels etc.
True, and RCA figures again Apollo 15 with yet another field sequential camera.
https://www.hq.nasa.gov/alsj/ApolloTV-Acrobat5.pdf https://www.hq.nasa.gov/office/pao/H...CTA-Report.pdf Peter |
17th Nov 2017, 5:15 pm | #38 |
Hexode
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Re: Colour Wheels etc.
Decades ago I remember seeing one of the cameras of the type that was used on these missions, I don't remember much of the detail except that the camera was quite small and that the shape of the filter segments on the colour wheel were not the regular shape that one might expect, the edges of the individual segments were much more of a sweeping curve rather than a straight line between the individual colour filter sections. I was told the reason for this distinctive shape, but unfortunately the explanation has faded into the mists of time passed.
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17th Nov 2017, 5:55 pm | #39 | |
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Re: Colour Wheels etc.
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18th Nov 2017, 8:12 pm | #40 |
Nonode
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Re: Colour Wheels etc.
I've just made this frame sequential RGB animated .gif. I can see it best in JASC 'Animation Shop' which I used to make it. It may run slow with little colour mixing if you just click on it here. Others may be able to suggest suitable software to view it, repeating endlessly, at a good speed. Or maybe re-save it into some movie format at your end...
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