alt Hacker NewsA lot of those CRT screens had a pretty low refresh frequency, you were basically sitting in front of a giant stroboscope. That was particular bad for computer screens where you were sitting right in front of them. I think they pretty much all displayed at 30Hz. I can imagine how a gigantic screen can get pretty uncomfortable.
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all CRTs televisions were either 60Hz or 50Hz depending on where you are in the world
Except CRT televisions weren't like that at all.
The only time the electron gun was not involved in producing visible light was during overscan, horizontal retrace, and the vertical blanking interval. They spent the entire rest of their time (the very vast majority of their time) busily drawing rasterized images onto phosphors (with their own persistence!) for display.
This resulted in a behavior that was ridiculously dissimilar to a 30Hz strobe light.
The limiting factor is the horizontal refresh frequency. TVs and older monitors were around 15.75kHz, so the maximum number of horizontal lines you could draw per second is around 15750. Divide that by 60 and you get 262.5, which is therefore the maximum vertical resolution (real world is lower for various reasons). CGA ran at 200 lines, so was safely possible with a 60Hz refresh rate.
If you wanted more vertical resolution then you needed either a monitor with a higher horizontal refresh rate or you needed to reduce the effective vertical refresh rate. The former involved more expensive monitors, the latter was typically implemented by still having the CRT refresh at 60Hz but drawing alternate lines each refresh. This meant that the effective refresh rate was 30Hz, which is what you're alluding to.
But the reason you're being downvoted is that at no point was the CRT running with a low refresh rate, and best practice was to use a mode that your monitor could display without interlace anyway. Even in the 80s, using interlace was rare.
Did they really do that, or did the tubes just ran at 2x vertically stretched 640x240 with vertical pixel shift? A lot of technical descriptions of CRTs seem to be adapted from pixel addressed LCDs/OLEDs, and they don't always seem to capture the design well
I recall a lot of people playing counterstrike at 640x480 to get at 100+hz refresh rates. The lower the resolution, the faster you can refresh. I don't recall the absolute limit but it would give the latest LCD gaming panels a serious run for their money.