Dale Kelly wrote:
flyback1 wrote:I started working in commercial broadcasting in 1967. I know what NTSClooks like in the studio.I was in London in 1982 and 1984 and my firsthand observations werethat at that time the PALtelevision system displayed on sets in people's homes made better,more detailed, more deeplyYes, I've also been there and done that and do agree that the video is superior. My point is that PAL does not define the number of scan lines nor the video bandwidth, which are responsible for much of the superior picture that we both observed.saturated color pictures than I have ever seen in any NTSC studio
I never said PAL defined the number of scan lines, and I know that PAL in Brazil and a few other places has only 525 lines, just like NTSC. When I said PAL, I meant the TV system in the UK that has always made better looking pictures than NTSC, and almost as good pictures as ATSC.
PAL only defines the 180 degree alternating color reference phase shift and the bandwidth available for the color signal, otherwise PAL and NTSC are identical. PAL design accomplished two things: 1. It resolved color phase error problems and also made the Hue control unnecessary. That was of more value in the early days but later broadcast and receiver equipment improvements minimized it's value.
The first early 'Simple' PAL receivers didn't have a delay line to do simultaneous decoding of the U and V color phases, so if you looked at the screen with a magnifying glass you could see a field of B-Y and a field of R-Y interlaced as alternating lines. Do you know what words U and V stand for and which component color value each represents?
Did you know that when RCA was inventing color in 1950, they tried an alternating color field scheme? Their version was called CPA, Color Phase Alternation, and Hazeltine's version of exactly the same idea was called OCS, Oscillating Color Sequence.
These schemes were used with the early RCA 'color sampler' circuitry, which was abandoned in favor of ??Philco's?? quadrature amplitude modulation scheme.
2. PAL's two color subcarriers have equal bandwidth while NTSC has different bandwidths for it's two color subcarriers ( I and Q). The Q subcarrier transmits colors on the blue end of the visual spectrum where the human eye perceives far less detail than it does at the Red/green end.
The Q subcarrier represents colors along the green-violet axis of the vectorscope, and Plus I was chosen because it represents fleshtone. The engineers at RCA felt there needed to be something readily identifiable in the picture, so they made the I vector fall on the point of the vectorscope where fleshtone is found.
Minus I represents cyan.An NTSC picture missing the I modulation component looks far worse than one missing Q.
Therefore NTSC designers reduced the bandwidth available to the Q signal so as to its reduce cross talk into the video signal, but they did provide full bandwidth for the more detailed I signal .
There were only two consumer TV sets that were built with full I & Q demodulation, the very first Westinghouse color set [the very first set to be introduced in 1954 beating RCA to the punch by ??a few weeks??] and the very first RCA set, the CT-100.
No color sets built from 1955 on, until around the late 1980s had I & Q demods. I think also the only TV studio monitor that had I&Q demods was the RCA round tube TM-21. Most NTSC TVsets were cheap and used narrowband X and Z demods.
In reality, there should have been no noticeable difference between the colors produced by the two systems (other than the phase issues).
On a 32 inch NTSC TV set, with FULL I & Q Demodulation all objects down to about 1 inch in diameter will be reproduced in all three colors, R,B,G. Objects between 1 inch and 3/16ths of an inch, will be reproduced only in Orange and Cyan through the I demodulator, if the set really has one. Objects in the picture less than 3/16ths of an inch in diameter will be reproduced in B&W.
However, along came the receiver manufactures, who in their zeal to minimize manufacturing costs, decided to filter both color signals at the lower Q bandwidth and thereby saved the cost of a delay line (maybe a dollar, if that). The receiver implementation is actually responsible for the superior color detail seen in the PAL system.
I think someone at RCA was quoted as having said the use of narrowband demodulation in their TV sets saved a lot of alignment headaches and one 1/2 watt resistor. This does not make sense to me because with narrowband demods you only need one dalay line as you said, the second delay line being needed to get the wider bandwidth I signal back in time with the slower, narrowband Q.
I believe that the designers of PAL, who had the benefit of hind sight, correctly made the decision to transmit equal color bandwidth to circumvent the NTSC receiver manufacturing issue.
There is always a penalty for being first.Someone else will come along later and improve on all your efforts without having had to do the 99% of the inventing you did, and they will badmouth you for not having done as good a job as they have. Such is the penalty for being a pioneer, and paving the way and making it easier and smoother for everything and everyone else that follows.
The NTSC Television System is still the most efficient in terms of bandwith conservation and the best overall compromise design of all the color systems in the world. If you want to read a comprehensive Color Television History, go here: http://novia.net/~ereitan