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Comment by mgiampapa | Hacker News Reader

Those Sony Trinitron's were literally were made of lead. My back still hurts, but the 20" was worth it!

Was that the one with the demagnitize button? I used to slap the monitor while pushing the button so my coworkers would think I hit it so hard the image bounced around

All the better ones had that button, usually named "degauss". My 22" flat CRT (it was flat on the front, like LCDs today, which was a great feature at the time, but made the thing extremely expensive and extremely heavy) had a degauss function that was apparently so powerful it visibly distorted the image on other monitors right next to it when I degaussed mine. I made a joke of doing that in the middle of games on LAN parties ;-) didn't work repeatedly though, after degaussing once I had to wait for some time until degaussing again would actually do something.

I made the mistake of pressing Degauss on a monitor while holding a magnet next to it.

This basically calibrated the thing to look normal... with the magnet there. It took quite a while to restore to normal.

Numerous monitors had degaussing features, Sony's among them.

And if they didn't, and somehow you managed to magnetize it, you needed to use a degaussing coil, moving it away from the screen in a spiralling motion... ah, the memories.

https://www.youtube.com/watch?v=3pVLizAHby4

I assume that by "somehow managed to magnetize it" you mean "had crappy detachable boom box speakers sitting on top of it in college, causing the TV to eventually display distorted blobs at the top edge of the image".

No? Huh, guess it was just me ;)

I honestly don't know. I picked up a Compaq monitor with a magnetized grille from the trash in 2002 or so, and used for my secondary pc (a venerable P200 MMX that took a LONG time to recompile the 2.4 kernel on a then-unstable Debian Sarge).

No idea how the previous owner managed to magnetize it, it never happened to me.

I did that, and figured out if you flipped the speaker around, you could "paint" the distortion away.

I finally replaced my aging CRT at work (3rd screen for unimportant stuff) after it finally died after 20 years of service. I still miss pressing the degauss button, which (perhaps relatedly) needed to be pressed after powering on and sometimes multiple times during the day.

And 120hz refresh rates... almost 20 years ago!

I never noticed a benefit over 70 or so. The flicker of 60 made my eyes bleed though. Then with LCDs 60 was fine.

I still don't know what it is about 60 Hz that made me see the flicker plainly as a strobing light. TVs at 50 Hz—nothing (other than being generally bleh back then). Had to use 800x600 instead of 1024x768 just to have 85 Hz instead.

On LCDs, I still can see faint flicker on some static backgrounds, and I think 60 Hz might play a role here too—though it seems to also depend on the brightness and Flux being on or off. E.g. on https://marctenbosch.com/news/

The LCDs you see this on are 6-bit color displays using temporal dithering to pretend to be 8-bit color.

That's why drop shadows look horrible when I'm looking at my screen at the wrong angle... I knew it was a dithering thing, forgot LCDs were 6-bit.

Only cheap/low-end LCDs are 6 bit. Most are 8 bit with no dithering.

Should this be the case with a Macbook, even if a sorta old one? Because that's the machine I've seen the flicker on, for the past bunch of years.

The reason for flickering on specific patterns is independent of temporal dithering. This is caused by cyclic polarity inversion: http://www.lagom.nl/lcd-test/inversion.php

(temporal dithering usually is visible as slight noise on darker shades)

AC power is 60hz so room lighting (especially florescent) also flickers at 60hz. It’s a sort of wagon wheel effect.

I dropped a hint right there that the AC frequency is definitely not 60 Hz where I am.

Actually you didn't. There were many countries that used PAL for TV broadcasts but have 60hz AC.

Hmm, afaik the framerates were chosen to be equal to the AC freq so that there are no glitches in the image. Do those countries have converters or something in the TVs, or did they watch jumpy image?

They didn't say PAL, they said "50 Hz TV."

PAL and 50 Hz TV are not synonymous. Brazil has 60 Hz AC and uses PAL-M which is 60 Hz TV. AC=TV even in these odd cases.

Old CRTs couldn't possibly clock their flyback to anything but mains.

Fluorescent lighting, assuming it's not starting to fail, flickers at 120 Hz because each half cycle lights it up equally (+ or - doesn't matter). Incandescent also has 120 Hz flicker but the valleys are almost as bright as the peaks (slow response) so it's essentially imperceptible.

Cheap LEDs like some holiday minilights are rectified so they'll flicker at 60 Hz and I can't stand them.

Three reasons: You sit much closer to a computer screen compared to a TV, so your peripheral vision has a better chance with the computer screen to see flicker. Computer CRTs supported higher refresh rates, so they used phosphors with shorter afterglow (otherwise you'd get ghosting/S&H-like artifacts like TFTs produce). You can notice this one when you photograph a computer CRT vs. photographing a TV with the same shutter speed. And at the end of CRT TVs a lot of them were 100 Hz.

Interesting hypotheses, though I still can't quite accept them as final. I seem to recall that the effect was much more noticeable, not only when sitting in front of the screen—basically enter the room and there it is. And I think that I've experimented with lower refresh rates too, at least I definitely had the time and inclination—but can't remember if the monitor allowed them with the available resolutions. It's stuck in my memory that only 60 Hz does this.

When I get rich and have lots of free time, I'll probably buy a bunch of old CRTs just to dig to the roots of this.

Btw, I count only two reasons there.

(1) You sit much closer ... (2) Computer CRTs supported ... (3) And at the end ...

Yeah, and I had 3d shutter glasses that worked great with the trinitron... In 2000 or so. Nvidia 3d Vision came along later but now sadly those product lines are abandoned, I guess due to VR which is just not what I want at all

Wow, such memories with the 3D Vision. Was quite visionary. And indeed I had to buy a Sony Trinitron with 120Hz refresh otherwise it wouldn't work.

I remember playing MoH:AA, the play experience was quite out of this world.

Coincidentally, my whole team still uses Nvidia 3d Vision 2 at work, despite lack of support from Nvidia. One of the reasons I took the job is because I saw they were using it. Not having access to those systems is one of the hardships of working at home. https://www.jpl.nasa.gov/news/news.php?feature=7638&fbclid=I...

Still the nicest displays I've ever used.

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