> 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
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.
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.
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.
Wow, and that ruler on the right side, even with the sound.
One of the nicest pages I have been on.
And the landing page... https://www.makingsoftware.com/
It just keeps on giving.
Each individual pixel is driven by a transistor and capacitor that actively maintain the pixel state? Insane manufacturing magic.
Dead pixels used to be a big problem with LCD displays. Haven’t thought about that in at least twenty years.
Everyone knows the obvious reasons we don't use crts any more.
It's true but it's a most uninteresting observation that only cares about practical aspects. Practical aspects matter, none of my own desks has a crt, but they do not define life itself.
Those facts do not at all invalidate the point about the desirable aspects which have been lost, or the fact that the merely interesting and remarkable aspects are interesting and remarkable.
The desirable and/or interesting and remarkable features of a crt are still cool, impressive, fun, desirable, even though we all voluntarily choose to use something else basically everywhere we want a screen because of the practical reasons that just happen to overwhelm.
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.
[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...
So yes, any image was extremely ephemeral at the time.
PS: Apparently it’s called a Noddy, it’s a video camera controlled by a servomotor to pan and tilt (or 'nod', hence the name Noddy): https://en.wikipedia.org/wiki/Noddy_(camera)
I read something interesting recent but I'm not sure if it's true or not. That as you age your integration frame rate decreases.
The exact sizes, shapes, and positions of the pigment dot triples (and/or the mask holes) are presumably chosen so that this holds even away from the main axis. Also, the shape of the deflecting field is probably tuned to keep the rays as well-focused as possible. Similarly to how photographic lenses are carefully designed to minimize aberrations and softness even far from the optical axis.
(*) Simplifying a bit by assuming that the beam gets deflected immediately as it leaves the gun, which is of course inaccurate.
[0] https://antiqueradio.org/art/RCACTC-11ConvergBoardNewRC.jpg
As a result monochrome terminal text has this surprising sharpness to it.(surprising if you are used to color displays). But the real visual treat are the long persistence phosphor radar scopes.
In a sense, all vision is.
Even "digital RGB" isn't digital in terms of the CRT. It's only "digital" because each color channel has a nominal on and off voltage, with no in-between (outside of the separate intensity pin). However, the electron gun still has a rise and fall time that is not instant.
Displays didn't truly become digital for the masses until the LCD era, with DVI and HDMI signals. Even analog HD CRTs could accept these digital signals and display them.
Monochromatic CRTs were well and truly resolution agnostic, there were legitimately no pixels or subpixels or anything similar to speak of. That said, the driving signal still had to be modulated to produce an image, and so it's not magic either. You can conceivably represent [0] all the available information in them using just 720 samples per line, which is exactly why DVDs had that as their horizontal resolution (720 pixels).
This story changes a bit though with color CRTs, where you did have discrete sets of patches of different phosphor chemistries called triads. There was absolutely a fixed number of them on a glass, so you could conceivably consider that as the native resolution for that given display, with each triad being a pixel, and each patch being a subpixel. The distance between these was the aperture pitch, much like how you have a pixel pitch on a typical flatpanel display.
The kicker then is that as you say, there's no strict addressing. From what I understand there were multiple electron guns scanning across the screen simultaneously, only being able to hit the specific color they were assigned, but the patch they were hitting wasn't addressed, they just scanned across the screen like the single electron gun did in monochromatic CRTs. You'd then get resolution invariance by just the natural emission spread providing you with oversampling / undersampling without any kind of digital computational effort. It's not really true resolution independence like with the monochrome ones, I'd say. I even recall articles where they were testing freshly released CRT monitors, and discussing how sharp the beam was, resulting in what kind of resolution adherence.
[0] an earlier version of this comment said "extract from" here; for various reasons you might already know, that's a different thing, and would not actually be true.
I was thrilled when my computer let me choose a resolution of 848x480, and it worked perfectly.
Back in those days, the web was usable at that resolution.
Even apart from that, a lot of laptops still have 1280x800 as the default resolution, and that's only double the width of 640x480. Honestly, I'd actually be more worried about OS and browser chrome eating up the space than websites themselves being unusable.
The input is roughly serial, so it takes a massive serial to parallel conversion.
Look at the connector pinout of the panel itself. There's only 50 pins or so, and a lot of them are grounds. Whether the scaler-to-panel format is eDP, or LVDS (FPD-Link), or V-by-One, it's all still differential serial lanes at that point.
Around the perimeter of the panel, then, are the actual TCON and row/column driver chips, bonded right to the ITO traces on the glass, flip-chip-on-glass style. These have an outrageous number of pins, and directly connect to the gate (row) and source (column) traces. It's here that the serial becomes parallel, and the next stop is the transistors themselves (hence the MOSFET signal terminology of gate and source) in the individual pixels.
Older displays would have basically a bunch of serial-to-parallel register chips with each one's SO connected to the next one's SI. I ran across a fasincating video of replacing a bad chip in such a display, which happens to be gas plasma so the voltages involved are also pretty high too:
DVI (and thus older HDMI) being essentially "VGA that skipped Digital to Analog conversion" you're riding the beam, including porches.
A CRT - to name one - is a device whose actual understanding will challenge people in profound ways. To ask “how does a screen even work?” and to begin to answer this question will require a bit more than a summary form of “thing goes from point A to point B”. The history of this discovery is a stack of books and in and of itself is fascinating - the experiments and expectations and failures and theories as to why and how. I suppose I just expect more of the site. The illustrations are nice. Oh and my moniker is just a coincidence.
Phosphorescent blue OLEDs should reduce current OLED display energy usage by 20-30%. But it still seems to be way off for phones and mass usage.
But OLEDs just have too many advantages where it actually matters. Much lower power consumption, physically more compact (no need for backlight layers), etc.
YES, OLEDs consume less power, offer truer color reproduction, and are physically more compact.
BUT, they are prone to CRT-like burn-in.
SSDs, the same thing.
YES, SSDs are much faster and immune to mechanical failure.
BUT, they tend not to last as long as HDDs due to limited write cycles, and their price per GiB is still much higher.
In terms of TV. LCD have higher peak brightness. The Sony Bravia 10 will be out soon, hopefully it will showcase the world what LCD could be.
Not to mention cheaper at larger size panel.
Would be nice if you could give a hint on all the disabled chapters. Either a tooltip or even just a title attribute. Are they paid? Do I have to login? Not ready yet?
A few decades ago I worked on a huge machine that made LCD color filters.
> How do you make the illustrations?
> By hand, in Figma. There's no secret - it's as complicated as it look
What is astonishing about LCDs? I don't mean to diminish the difficulty of scaling up the process, but if you think of early LCD displays they don't seem farfetched to be shipped to consumers.
It's all engineering but it's surprisingly hard to move things from the lab to manufacturing at scale. Years and years and lots of problem solving. Some efforts/approaches fail and you never hear of them.
It’s late and time for bed! LoL.
Wonderful content and website otherwise!
