#16
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PAL/NTSC why wait?
I think us Brits were probably right to wait; the problem with any standard is that once adopted, research into better ways of doing whatever it is become stifled by having to be compatable with `the standard'. One thing that's always puzzled me (wildly off topic but it's night time, maybe no-one will notice). VCR manufacturers extended recording time by halving the tape speed and accepted the trade off of lower definition in favour of extended recording times. Why did they not make machines that would record at double speed; a 4 hour standard speed tape would contain 2 hours of higher definition video for special recordings. Was there some technical reason why this could not have been done?
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#17
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Although I am no expert in this field, the primary limitation with standard domestic VCRs, was and is the luminence under chroma recording method.
This limits the luminence ie monochrome resolution to around 240 (VHS) 270 Beta) lines. Both SVHS and Beta ED extended the resolution to around 350-400 lines for SVHS and up to 500 lines with Beta ED. Buth this required metal tapes and substanitally revised electronics. Of course from the early days of vcrs there was always the option of Laserdisc and in even CED disks which offered superior images. Both formats had issues (CED didn't survive for very long in the NTSC market let alone the PAL market). But back to NTSC 405 line which was an option for the UK ....in many cases 625 line tv sets both colour and black and white, especially early colour sets would not have been much "sharper" than their 405 line cousins so waiting 15 years or more to go to colour didn't really add much. The sad part of the UK not adopting colour in the 50s is that all those great BBC dramas from the 50s and 60s are only black and white!
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____________________________ ........RGBRGBRGB ...colour my world |
#18
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Last edited by andy; 12-07-2021 at 02:21 PM. |
#19
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The development of slant azimuth recording made it possible for Beta and VHS to to use much less tape than previously needed.
"Slant azimuth recording" means that the recording heads are not in line with each other but are offset by a small amount ...again apologies if I am a little inaccurate here..but with VHS I think it 6 degrees and beta 7 degrees ..or something similar. This enabled Beta and VHS to do away with guard bands betweens each head pass over the tape effectively doubling the capacity of the tape. The main difference between recording speeds is not resolution so much as signal to noise response. Hence LP and EP etc for VHS and BIII on Beta resulted in less saturated colour and noisier images with increased delta gain. This is also why the improvements in tape were so important and made it possible to introduce the lower speeds. (And also the introduction multi head recorders with the different heads optimised for the different speeds resulting in much better low speed recording). The introduction of HiFi recording for vcrs is whole 'nuther story since the spec for NTSC Beta enabled the sound to recorded in a "gap" in the signal, whilst with VHS this was not possible and resulted in the so called depth multiplex system with the sound signal recorded under the video signal. The PAL Betas uses the same system as VHS to record HiFi as the signal spec does not have the "gap" utilised by the NTSC variant. (In fact NTSC Beta introduced HiFi stereo some time before it was available for VHS or for PAL Beta). Of course the other significant tape development was the new bases which were thinner but capable of handling the stresses imposed in the recorders without stretching. If you can remember the dim dark ages (ie the early 80s) VCR tapes came in basically one length L500 (two hours as NTSC BII or 2hours 10 minutes for PAL) and L750 (3 hours for BII and 3 hours 15 minutes for PAL Beta), and T120 NTSC or E180 for PAL VHS. PAL Beta never adopted slower recording speeds.. there was no BIII for PAL Beta. VHS T120 cassettes gives 2 hours at SP on NTSC but 3 hours on PAL ...this is due to the different frame/line rates. 625x50 does not equal 525x30 ...the heads spin more slowly (1500 as opposed to 1800 rpm) so PAL recorders use less tape. The T160 (E240) tapes arrived by about 1984 and the L830 by '85. T200 tapes (E300) arrived in the early 90s...but were intially very expensive.
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____________________________ ........RGBRGBRGB ...colour my world |
#20
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Last edited by andy; 12-07-2021 at 02:21 PM. |
Audiokarma |
#21
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There were also Color TVs that used a Color Drum instead of a wheel around
a 17 or 20 inch B/W CRT. |
#22
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Drum or Cone? Direct View or Projection?
Quote:
However, I have also seen the same set in pictures with front and rear shots, described as a projection set, and indeed the rear photo shows a small CRT and a Schmidt optical system but the color filters are built into the shape of a cone such that the light from the optics passes through one side while it spins, bounces off a large mirror on the rear wall and onto the screen. The optical system is nothing I have seen before or since. It is not anything familiar, like the RCA KRK1-1, or the Philips Protelgram or the systen used by Philco with their TP-400 CRT. Not only this, but I have also seen this picture ascribed to more than a CBS prototype, but I can't remember the name of the other manufacturer. Could CBS have given the cabinet to someone else to build a different system into? Does anyone have a definitive answer to this mystery? |
#23
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Backside photo I have
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#24
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RCA, in their book "TELEVISION VOLUME 4 1942-1946", has a color camera with a color wheel and color wheel, color drum TVs. They also had a projection color TV using three 2 inch CRTs each with its own color, with lens from overhead projectors.
CBS or RCA working with PYE? Someone else? |
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