How does a screen work?

There are some sentences in this that are technically vague enough to pass, but I don't think are strictly speaking correct, and I believe will likely lead to a mistaken understanding:

> modern displays don't paint the image line-by-line (...) They light up each pixel simultaneously, refreshing the entire display at once.

The entire screen area is lit all the time now, yes, but refresh still typically happens line by line, top to bottom [0], left to right [0], for both LCDs and OLEDs. It's a scanning refresh, not a global refresh (sadly).

You can experimentally confirm this using a typical smartphone. Assuming a 60 Hz screen refresh, recording in slow motion will give you enough extra frames that the smartphone camera also likely operating in a scanning fashion (rolling shutter) won't impact the experiment. On the recording, you should see your screen refreshing in the aforementioned fashion.

[0] actual refresh direction depends on the display, this is for a typical desktop monitor

I was glad they at least mentioned how IPS (PLS) and VA differ from older TN.

But you're right both LCD and OLED refresh a stored voltage on the cell (or caps) on a roughly line by line (OLED can easily be 5 clocks on the GIP to cancel internal transistor offset voltages).

I was mostly annoyed that they didn't mention the circular polarizer on OLEDs. Although there is discussion of going to color filters with Quantum Dot OLED, the circular polarizer is what makes the blacks so black on mobile OLED devices.

Also, didn't really mention pentile RGGB sub-pixel pattern which is dominant in mobile OLED (which is more than 50% of devices). Now they're moving to "tandem" stacked OLED for higher brightness and lower current density, but no latteral sub-pixel pattern.

There were a few things I personally found lacking as well, albeit they're fairly minor.

Regarding CRTs, at the vector CRTs section, they mention "they were mostly monochrome and so the phosphor dots could be tightly packed" - this is not true either I believe, monochrome CRTs had a uniform phosphor coat on the inside, no subpixel patches. I'd have also liked if they delved a bit into the decay times of the various phosphor chemistries used for color CRTs, and how they compare to LCDs and OLEDs. It's an entertaining comparison, grounds motion performance related discussions really well.

Regarding LCDs, I missed the mention of multi-layer LCDs, especially since they bring up tandem OLEDs.

Regarding OLEDs, now that you mention, the subpixel layouts were left unaddressed.

Regarding quantum dots, I missed both the mention of QDEL as a somewhat promising future contender, and the mentioning of the drawback of their typical implementation. External light also provides them with energy to activate, which I believe is at least partially the cause behind the relatively poor black levels of QD-OLEDs in environments with significant ambient light (+ something about it not being possible to put a polarizer in front of them?)

I was also generally expecting a more in-depth look by the title, would have loved to learn about the driving electronics, maybe learn about why OLEDs aren't ran anywhere near as fast as their full potential (I'd assume throughput limitations), etc. Overall, it basically only covers as much as my own enthusiast but not in-the-area self gathered over the years too.

Indeed, one feature of active-matrix (and even passive-matrix) displays is that it needs only m + n signal lines to address a pixel in an m + n display. To change the color of a pixel, a signal goes out over the lines corresponding to the row and column of the addressed pixel, selecting it; and then another signal is transmitted over another line to actually change the value of that pixel. In this scheme, it would be impossible to address all pixels simultaneously. Nor would you actually want to, as this would require millions of control lines to drive the display!

> Regarding CRTs, at the vector CRTs section, they mention "they were mostly monochrome and so the phosphor dots could be tightly packed" - this is not true either I believe, monochrome CRTs had a uniform phosphor coat on the inside, no pixel patches.

This is one of the reasons why emulated versions of Asteroids (arcade game) can never match the real thing: the razor-sharp, perfectly straight lines with zero aliasing used to paint the display. The computer also has fine-grained control of how bright to make the electron beam that raster displays typically don't allow (this is perhaps as simple as holding the beam in place, or drawing back and forth over the same line segment), meaning that your ship's projectiles and enemy shots appear as super-bright points with a phosphor bloom around them, glittering in the dark. Most emulators simply draw them as nondescript pixels. I suppose with some effort a CRT simulator can be hooked up to the emulator... but it still wouldn't be the same.

I'm glad I got to play an authentic Asteroids before I died. Working machines are getting rarer. Some of those who come after me may not get that chance.

My first and only time playing Asteroids in its original vector CRT glory was a bit shocking to me. I remember the evolution of CRTs in the 80s and 90s. My family had a small B&W CRT that fascinated me with its image quality, in that it always reminded me more of a b&w photo than color CRTs reminded me of color photos.

Still, that vector CRT that I saw perhaps a dozen years ago was quite a surprise. Lack of rastering and the utterly insane brightness sent me down a rabbit hole. I ultimately concluded I'm not ever likely to own a basement Asteroids cabinet.

The article also assumes all LCDs are transmissive, and the bulk are, but reflective (and transflective) LCDs are a thing.

I don't know how common it is now, but a lot of high-resolution LCDs with dual LVDS interfaces were essentially two separate panels, with one lane feeding the top half and the other the bottom half.

Assuming a 60Hz refresh rate, does it take ~16ms (± the vblank inteval) for a complete cycle from top-left to bottom-right? Or does the scan happen faster than that (with something else being the limiting factor on overall refresh rate)?

Yes, the refresh cycle takes ~16.6 ms. There's another "point" chasing behind the refresh "point", that will be where the panel's response time has finished catching up with the refresh. In between these points, the pixels are slowly morphing from one color to the next. On LCDs, the area between these two points is quite sizeable, definitely more than a few lines, sometimes even hundreds of lines. On a 1080p 60 Hz display, just 1 ms of response time corresponds to 64.8 lines (6% of the screen) being constantly in flux, for example.

The difference between LCDs and CRTs in this regard then, is that on a CRT you only ever got light during that chase section. The initial state is full darkness, and the final state is full darkness too. It's a pulse.

Maybe slightly off topic but I was surprised to discover that my glasses with photoreactive lenses (SpecSavers ‘Reactions’) are actually circularly polarised but only when they go dark. I originally thought they didn’t work because they didn’t interact with another pair of polarised sunglasses (no changing brightness as I rotated one lens in front of the other) but later noticed that my phone screen with its circularly polarised IPS screen was almost black in bright sunlight… until I took my glasses off.

I had similar reactions, only it all happened while I was in grade school!

Oh yes! The bright projectiles really add to the game impact. And on some cabinets, the lines were not perfectly straight. It looked for all the world like the phosphor coating had a bit of texture to it. Now being older, I realize an effect like that could just be a marginal DAC too.

IMHO the best vector experiences, in order are:

STAR WARS

This is a color vector display cranked up to the nines! The processor handling the vector drawing is fast! Tons of vectors are possible with only subtle impact on display refresh speed and overall quality. There is some global image size artifacts that happen when some of the brightest objects occupy a significant percentage of the display.

And that is a feature! Love it. Get into a sit down cabinet if you ever get the chance.

TEMPEST

This game is not for everyone. Most of these drive people to their limits, but TEMPEST ramps up and beyond normal human limits! Not everyone can play this game at its peak. Same can be said of nearly everything on this list, but without that aggressive ramp up.

ASTEROIDS

I prefer the original cabinet with the somewhat slower object motion. That one is a bit easier to play. Depending on the operator and how hard they drive the CRT, image brightness ranges from a bit old, washed out and tired looking to WOW! How do those tiny projectiles not just carve a line right into the phosphors.

Cinematronics games: TAIL GUNNER, STAR CASTLE, RIP OFF.

These use overlays for a bit of color. Oh, I forgot ARMOR ATTACK, which uses large ones like STAR CASTLE.

The quality of the vectors is not quite as good as the ATARI displays and this too is a feature. That gives Cinematronics a bit of charm I find quite enjoyable

And sound! Hoo boy! STAR CASTLE has great, loud --> I mean loud sounds with full bass notes able to rumble you and the cabinet!

OTHER COLOR VECTOR GAMES

I like playing all of these, but they simply were not peak experiences. Still damn good, if you ask me:

MAJOR HAVOC, GRAVITAR, A Two Player tandem Asteroids game I cannot recall. Fun though!

And last place: QUANTUM played with the Trackball. You circle atoms over and over. This game looks cool and is hard.

GRAVITAR uses the Asteroids movement dynamics to great effect! A fun thing in this game is massive changes in scale happen often. Rare to see.

Vector gaming delivered many of my very highly cherished arcade gaming experiences for sure.

ATARI and Tektronix deserve special mention in this context:

Atari made color vector games work! Did anyone else? Those look amazing! And hold up today in my view.

Tektronix invented both a pure storage tube CRT. Their graphics terminals often doubled as Minicomputers programmable in Tek Basic. The large ones offered a 4K vector space! Crazy good detail for the 70's. And one in good condition, operating in a reduced light room is beautiful to use.

My first manufacturing CAM software experience was on one of these. Used a fixed record length cassette so that many "files" could be accessed almost like a floppy disk drive. User data went right to the paper tape puncher / reader. 1200 baud punch, reads could be faster, up to 9600, if one had a good reader unit.

One ran applications from that cassette and stored and used user data from the paper tape.

But I digress!

Right near the end, Tek managed to get both storage graphics and dynamic refresh capable graphics, both in a different color. I only got to use one of those one time. I loved it because many different work flows were possible.

Man, for the chance to code a UI on one today!

One last thought: in my view vector displays are best on a CRT, mostly because of the image contrast and speed possible, but great vector experiences can also be had on a wall, or perhaps a screen with some coating to bring out the best possible.

We may yet see vectors appear from time to time in these and other ways simply because of how great they are. Hope so, and building a small, color capable one using a low power laser and screen with coatings sure to deliver motion trails is on ky bucket list.

> My family had a small B&W CRT that fascinated me with its image quality, in that it always reminded me more of a b&w photo than color CRTs reminded me of color photos.

The problem of a finite dot pitch interfering with image quality, especially on small displays where the dots were necessarily larger relative to the image size, is what motivated Tektronix to develop field-sequential color CRTs which they used in their digital oscilloscopes in the 80s and 90s. JVC also used the technology in some professional broadcast video monitors. Basically it was a B&W CRT with a changeable (liquid crystal) color filter in front of it. The R, G, and B channels would be shown one after another with the corresponding filter activated, in a similar manner to a color wheel DLP projector.