by Klaas Robers » Mon Apr 23, 2007 11:56 pm
I doubt that a field sequential system could ever give reasonable colour rendering, when you use a normal black and white picture tube and a colour filter wheel. What only a few people know is that black and white picture tubes use two phosphors to simulate white, it is blue and yellow. If you have a black and white TV still operative and a magnifying glass, please look very carefully to the screen of the TV in a dark environment and you will see blue and yellow grains of phosphor on the "white" screen. A "snowing" screen is good enough, analogue transmissions are not needed for the observation.
With only yellow and blue you will never get red and green from the screen. This is the problem with our eyes that don't SEE the difference between a mixture of blue and yellow, a mixture of green and magenta, a mixture of red and cyan or a mixture of red, green and blue . All four can show us the same impression of white.
Of course white picture tubes could be made that synthesise white from red, green and blue, just like the better TL-tubes nowaday do, but as far as I know this has never been done. The need for better colour rendering initiated around 1960 an enormeous research effort to get an efficient and good red giving phosphor. This resulted in the Europium (strange earth metal from the range La-Lu, the so called Lantaniden) doped red phosphor.