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How does a screen work?

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572 points chkhd | 2 comments | 13 Jul 25 14:09 UTC | HN request time: 0.454s | source
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retrac ◴[13 Jul 25 16:39 UTC] No.44551618[source]▶
CRTs are still slightly magical to me. The image doesn't really exist. It's an illusion. If your eyes operated at electronic speeds, you would see a single incredibly bright dot-point drawing the raster pattern over and over. This YouTube video by "The Slow Mo Guys" shows this in action: https://youtu.be/3BJU2drrtCM?t=190
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hinterlands ◴[13 Jul 25 16:59 UTC] No.44551773[source]▶
That slo-mo video is somewhat misleading, though. The phosphor glows for a good while, so there is a reasonable chunk of the image that's visible at any given time.

The problem in that video is that the exact location the beam is hitting is momentarily very bright, so they calibrated the exposure to that and everything else looks really dark.

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layer8 ◴[13 Jul 25 18:31 UTC] No.44552411[source]▶
The phosphor still drops off very quickly [0][1][2], roughly within a millisecond. That’s why you would need a 1000 Hz LCD/OLED screen with really high brightness (and strobing logic) to approximate CRT motion clarity. On a traditional NTSC/PAL CRT, 1 ms is just under 16 lines, but the latest line is already much brighter than the rest. The slow-motion recording showing roughly one line at a time therefore seems accurate.

[0] https://blurbusters.com/wp-content/uploads/2018/01/crt-phosp...

[1] https://www.researchgate.net/figure/Phosphor-persistence-of-...

[2] https://www.researchgate.net/figure/Stimulus-succession-on-C...

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wincy ◴[13 Jul 25 18:41 UTC] No.44552480[source]▶
I definitely like my new 240hz 4k oled HDR monitor, though. They're getting there! The data rate it's pushing through the displayport cable for uncompressed 4k HDR is something 80gb/s though. Absolutely mind boggling. Huge upgrade from my 1440p 165hz IPS monitor that had huge amounts of smearing when playing games.
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1. BenjiWiebe ◴[13 Jul 25 20:53 UTC] No.44553640[source]▶
What model is your new monitor?
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2. wincy ◴[14 Jul 25 13:50 UTC] No.44560252[source]▶
The ASUS PG27UCDM 26.5" 4K UHD (3840 x 2160) 240Hz Gaming Monitor [0] paired with an RTX 5090 for my home desktop, but I got a USB switcher (for peripherals), and keep it on my standing desk that I plug in my work laptop too with a USB-C to DisplayPort cable. Only 60hz on the work laptop but I really like having a quad monitor setup in a T shape (3 27” monitors and the laptop plugged in with screen open below the central monitor, which is the OLED). It’s great for both productivity and for gaming. I turned off HDR for work, though.

The only annoying thing is every couple hours it asks me to run a 7 minute pixel refresh cycle to avoid burn in, but according to the dashboard I run it every 2.5 hours or so when I go on breaks, so I think I’m good.

Overall the monitor is just fantastic, my LAN party buddies and I dreamed about OLEDs like this back in 2003 and kept saying it was “just around the corner”. The biggest thing is in dark scenes in games there’s absolutely zero noticeable smearing.

[0] https://www.microcenter.com/product/689939/asus-pg27ucdm-265...