question about early color tv

[old_tv_nut]

There's some confusion in the discussion of phosphors above.
Original NTSC tubes (15GP22) used non-rare earth red (very inefficient), P1 (Willemite, oscilloscope tube) green (which was less yellowish than modern green), and a blue that was not so deep violet-blue as today's tubes.

21AXP22 still did not have rare earth red. At some point the blue moved more towards modern blue. The green was still P1.

Later, all-sulfide tubes were introduced, with better efficiency of the red and green, but the red was slightly more orange and the green was definitely more yellowish. The blue also had moved to the modern blue. The yellower green eventually caused a change to be made to the color demodulators to get good fleshtone hues, by increasing R-Y gain - but this tended to overdrive the reds, making them overly bright as well as slightly more orange than NTSC. This effect tended to mask subtle differences in red objects, especially if the color was turned up.

The eventual use of rare-earth red made the tubes even brighter and more efficient, but did nothing to change the flesh-tone correction and overly bright reds. This situation continued forever in NTSC. Meanwhile, in Europe, PAL decided to matrix their cameras for the modern green phosphor instead of increasing R-Y gain in the receivers. This results in proper reproduction of both pale (skin) and saturated reds, and is essentially the same tack taken in HDTV (and digital still cameras and computer monitors, where it is called sRGB) today.

In summary, a lot of the complaints about the orangy reds, etc., of certain vintages of CRTs are not so much from the phosphor differences as from the chroma demod / matrix differences as manufacturers tried to get acceptable flesh tones. The reds in HDTV and PAL look much better than in NTSC even though the tubes use essentially the same phosphors. The ultimate greens and reds, of course, are NTSC on a 15GP22 - but its magentas and purples are paler because of the more cyan blue phosphor.