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Of the 1977 trinity, the PET and TRS-80 came with monitors built around black-and-white TV tubes, and the Apple II was commonly used with a black-and-white TV set.

According to https://en.wikipedia.org/wiki/TRS-80

The color of the 12 in (300 mm) KCS 172 RCA monitor's[13] text is faintly blue (the standard P4 phosphor used in black-and-white televisions). Green and amber filters, or replacement tubes to reduce eye fatigue were popular aftermarket items. Later models came with a green-on-black display.

Complaints about the video display quality were common. As Green wrote, "hells bells, [the monitor] is a cheap black and white television set with a bit of conversion for computer use".[50] (The computer could be purchased without the Radio Shack monitor.)[25] CPU access to the screen memory causes visible flicker...

Setting aside the part about flicker, which was unique to the TRS-80, it seems many people also had issues with the P4 phosphor. But the latter was not unique to that machine; it was common to all three. Why did people only object to it in the case of the TRS-80? Was it because 64 columns (as opposed to 40 for the other machines) exacerbated the problem? Or did people also have a problem with it on the other machines, and that just didn't get recorded for posterity? I note the PET did use a green monitor in subsequent models.

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    I picked up a TRS-80 Model 1 at an estate sale a few years ago and I didn't see anything obviously strange about the monitor's image quality. The case is cheap plastic, but the picture seemed OK. imgur.com/a/cXf4pnk
    – Darren
    Commented Mar 13 at 23:41
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    The higher horizontal resolution could have made the image fuzzier than the Commodore PET or Apple II image, increasing eye strain. Even though it was monochrome, 384 pixels (64x6) is a lot for a TV screen compared to 320 (40x8) on the PET and 280 (40x7) on the Apple II. Combined with the flicker, the eye strain might have been a lot worse than the other systems. Another issue could be the blue in the pixels as blue is harder on the eyes, which is why green (without blue) was preferred. This would explain why people bought filters.
    – Tim Locke
    Commented Mar 14 at 1:53
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    An expedition to a computer museum to do field tests may be in order 🙂 Commented Mar 14 at 22:35
  • The fact that the video output was momentarily blanked when accessing the frame buffer could be described as a kind of "flicker" that wouldn't be present on competing computers, and wouldn't be as noticeable on longer-persistence displays.
    – supercat
    Commented Mar 16 at 20:28
  • The article linked from the Wikipedia page is about how every piece of the TRS-80 in general is extremely cheap, but of good value for the price. It is not specific to that component and probably a bad choice of citation for their being particular problems unique to the TRS-80 screen. It may just be that this monitor was literally constructed cheaper and simpler than most competitors.
    – davolfman
    Commented Mar 22 at 0:32

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