These Are Not Pixels: Revisited

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When I first made a video on analog color television, the thumbnail I created (and its explanation) caused nearly endless debate. I thought I'd try and clear this up a bit.

Here's the video on how analog television works (you may notice I recycled some footage from it)

And the larger Television playlist:

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[TechnologyConnections]

Howdy!
Just to make a clarification, the three electron beams inside the tube are all the same--they are not actually colored, Red, Green, and Blue. It's the phosphors at the front of the tube that glow when they are hit with their corresponding beam--it's not like the picture tube is actually projecting three different colors of light. The principle is the same, though. You just need to substitute light for an electron beam for any sort of practical demonstration to be possible.
Hope that makes sense!

[MattMcIrvin]

The thing that really brings the distinction home for me is that with the closeup of the slot-mask CRT, you can see clearly that the brightness of the image can vary within a single phosphor dot, in a nontrivial way depending on the shape of the image (rather than the color or brightness data at a single spot). That would not be the case if they were truly pixels.

Of course, the issue gets confused somewhat by the way that systems with LCD screens can do "subpixel rendering" by tweaking the color data in a manner that exploits the spatial arrangement of the red, green and blue elements to provide a bit more spatial resolution. But from the physical LCD's perspective, it's just rendering color data as usual.

[overloader]

"Theres no regularity in this noise" yt compression: allow me to introduce myself

[onedeadsaint]

Dude! your production value on this is amazing! that editing on the B&W TV was just 😙👌

[JohnMichaelson]

If you're a really old school PC gamer, you might remember that early high resolution color CRT monitors used to have the dot pitch heavily touted as one of their key attributes in advertising. Smaller was always better because it meant more phosphors being lit per sweep and thus a sharper image with more detail in areas of rapidly changing pixel values.

[WolfCoder]

"In this video I'd like to revisit a concept from my television series"


Many people can have a television series, but there's only one person who can have a series ON televisions

[smallmoneysalvia]

Wow! Nice practical demonstration of a shadow mask, super simple but it gets the point across really well. I’m impressed.

[staudinga]

12:27 "I mean, you can't really blame it. It only has 5 inches to work with."

That's what I keep saying!

[reggiebenes]

Excellent explanation. I've worked with arcade games for 30 years, and have tried to explain to my 9 year old the difference between analog and digital video signals. I finally had her watch your video series on it, because you are much better at explaining it, now she understands. I know it's just semantics to call it a pixel, but no matter how it looks you can't change the mechanics of how a CRT works. Great videos.

[asleeperj]

Youtube compression HATED that snow on the CRT

[macronencer]

I learned about how colour TV works when I was 10 (that was 1975), and was quite obsessed with it for a while. I remember explaining it to other kids in my class at school. This is an absolutely perfect educational essay - thank you! Younger people now won't remember the older tech, but if I had to choose something to go into an archive for future generations to understand how things used to work, I'd choose this video. 10/10.

[FinlayDaGk]

"for those of us with normal trichromatic color vision anyways"
Goddammit, I almost wanted to write: "*laughs in colorblind*"

[fragalot]

Also keep in mind the electron gun in the back of the tube isn't emitting any color. The color comes from the phosphorus panel just behind the face of the screen that get lit up as it's hit by electrons.

[alexatkin]

This is great, for the first time I can understand where the huge difference in CRT quality, especially multi-sync monitors comes from. The higher the feed resolution, the finer the shadow mask needs to be in order to avoid pixels of data effectively being lost because whole pixels worth of data are hitting the shadow mask instead of the phosphors.

[fwiffo]

One detail which I'm sure you sensibly omitted for time: you *can't* reproduce all visible colors with three primaries. You can only produce those inside the gamut of those primaries (a cube-ish shaped subset of all visible colors.)

Some high-purity colors lie outside the gamut. E.g. high saturation cyan can't be reproduced because the green phosphor stimulates the "red" cones somewhat, producing a less saturated color.

These colors are less common in natural images, so it doesn't matter much.

This is why a lot of modern displays have an oversaturated image; they have higher purity color elements, which increase the coverage of the gamut. The most common color standards are based on older tech, so new displays require color correction, which is usually not present because most people don't care if the color is wrong.

[iivarimokelainen]

I think the nail in the coffin would have been you sending a BW Kingdom Hearts image to the small CRT TV, showing the (now visible) numbers and letters. Or even sliding the saturation of the signal from BW to color.

[djp_video]

I think you missed a point to help convey your message...

If you pause at 13:58, you can very clearly see that each phosphor dot is actually displaying information from more than one scanline. Sure, some dots are fully lit equally from top to bottom, but many are not -- the top of the dot might be one scanline, and the bottom another. If you look closely enough, you can even see that there are changes in the intensity horizontally within a single dot. The bottom line is that if you were to try to correlate a phosphor dot to a "picture element" the dots are actually displaying multiple elements of the picture simultaneously, and are thus not a single picture element, or "pixel" as we have come to know them.

Similarly, (and you did sort of cover this) any detail in the image which doesn't fall within the area of the corresponding color of phosphor dot just isn't going to be visible. So, in theory, if you had a high resolution image made up entirely of very thin red vertical stripes on a TV with a particularly low dot pitch, it might be possible that you don't see anything at all if those stripes happen to line up in the shadow area of the screen. Also, if you have an RGB stripe TV (like a Trinitron) and a white edge of the picture happens to start on the blue dot and spill over into the red and green dots to its right, it will still appear as white, even though that edge is split across dot groupings. As mentioned, the TV just doesn't care where those dots actually are or how they are arranged -- it just displays what it can where it can and that's good enough.

[HuskyNET]

I’m a computer science student and I never understood how color CRTs with their dot masks worked. Thank you sir! That was a wonderful explanation!

[kjpmi]

I just want to say that you are amazing. I've learned so much from you. There are a lot of "good" YouTube channels, to be sure, but I'd label only a dozen or so as "great." Your videos are, without any reservations, right at the top of that list. You have a really nice way of presenting and it's clear that you aren't just reciting facts. You clearly have a deep intrinsic familiarity with what you talk about and that makes it so easy to learn from you. It would really be a sad day if you ever stopped making these videos. I sincerely just wanted to say thank you!

[garydunken]

Anlaog B&W technology without any microprocessor, software and importantly no software bugs! That was amazing. The color tech was later introduced to back backward compatible with B&W sets, like you said they use the same signal with added chroma signal. Again amazing thinking by our predecessors.