Crt effects list

RetroArch Additions Shaders
#1

01- Phosphor Blooming in Scanline (increase in thickness in areas where the scanlines are brighter)

02- Phosphor persistence (Afterglow or Phosphor decay)

03- Crt-breathing (raster-bloom)

04- Crushed blacks that happen side-by-side with “3- crt-breathing” when picture went bright

05- Some CRT geometry adaptively or temporarily changes with “3- crt-breathing” too

06- Glow (Halation), around bright areas of the screen (especially on dark backgrounds) as the light passes through the CRT glass

07- CRT Masks for Color Phosphor (shadow mask (dot phosphor delta gun), slot mask and aperture grille)

08- Overdriven electron guns (wearing electron guns smearing to the right)

09- Switching resolution glitch (or noise), out of sync v-hold?

10- Scanline effect

11- Convergence

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Koko-aio shader discussions and updates
#2

Examples for effects:-

01- reddit link

02- reddit link and youtube link

03- reddit link or youtube link #1 or youtube link #2

04- youtube link

05- youtube link or reddit link

06- effect similation and Real CRT example

07- imgur link (similation) and reddit link (Real CRT)

08- reddit link

09- libretro forum

10- wikipedia image

11- reddit link

Did I forget something? (the effects of connections such as composite video doesn’t count; this is a topic for CRT effects in general) also I would be grateful if you could provide a list of available shaders for each effect

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#3

For my shader specifically:

01- Phosphor Blooming in Scanline - Supported in Scanline Classic

02- Phosphor persistence - Supported in Scanline Classic

03- Crt-breathing - Not supported; adjusting geometry according to brightness is easy, however, the temporal breathing effect requires feedback and IMO is not worth the complexity.

04- Crushed blacks that happen side-by-side with “3- crt-breathing” when picture went bright - I’m skeptical if this is real and not just an optical illusion or something caused by ringing from filters.

05- Some CRT geometry adaptively or temporarily changes with “3- crt-breathing” too - Not supported; the trouble with this one is that it needs to work with 3 and requires looking at neighboring texels, so you have a complicated multipass 3-D shader on your hands.

06- Glow (Halation), around bright areas of the screen (especially on dark backgrounds) as the light passes through the CRT glass - I think you’re conflating multiple things here. There is the overall glow of the picture against the CRT bezel. There are also internal reflections from the glass. The internal reflections are, IMO, overstated and not that visible in real life. There are also other sources of blurriness that contribute more to the look of the picture: signal bandwidth (out of scope) and the focus of the electron beam. Electron beam focus is supported by Scanline Classic.

07- CRT Masks for Color Phosphor (shadow mask (dot phosphor delta gun), slot mask and aperture grille) - Supported by Scanline Classic (using already established subpixels masks, nothing innovative beyond that); I don’t think masks look convincing in SDR. It really benefits from HDR and 8K.

08- Overdriven electron guns (wearing electron guns smearing to the right) - Not supported

09- Switching resolution glitch (or noise), out of sync v-hold? - Not supported

10- Scanline effect - Supported

11- Convergence - Not supported, was more of an issue for projector-type screens IMO, but some error at the corners could happen.

Some additional effects:

12 - Vignette

13 - Color distortion due to proximity to magnetic fields (Gauss)

14 - Geometry and moire patterns (the two are related) - Supported by Scanline Classic

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#4

Excellent contribution @anikom15, although I may not agree with some of it

did you see this? https://youtu.be/zDvwfRGfZwQ?t=189 and I saw it back then myself

I think same feedback can be used for #03 and #04 and #05

I think that called “bezel reflection”? which is not directly related to CRT itself

and thanks for mentioning “additional effects” 12-14, I think we can also add “15- curved”

#5

These are related, are due to a poor-quality flyback.

One more thing. The glow effect itself is the same as the blooming effect, but some monitors have double glass (to make them look completely flat and create that striking glow effect). I don’t know of any TVs that do this, but I have seen it in arcades with double glass.

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Would it be possible to create an adaptive brightness shader?
#6

I also felt that they were, but for all CRTs (TVs and PC monitors) that I encountered in my life, I remember all of them has those effects but with varying degrees, also all cases in internet say so (including if you saw examples of these in the second post)

did you see the #06 in Examples?

I think most of old CRTs has double glass, see this https://youtu.be/JfZxOuc9Qwk?t=1682

#7

I’m not sure what the purpose of this list is exactly, but I might list a bunch that I don’t believe anyone has implemented yet:

  • Imperfect grayscale (red, green, blue out of sync)
  • Foldover (horizontal or vertical)
  • When something bright is in the overscan area, there is a larger, brighter glow with some barely-visible rainbow. (This is a lesser-known effect, so I doubt anyone has posted an example.)
  • Velocity modulation
  • Magnetized, uneven impurity (need to degauss) (already noted by anikom15)
  • Curvature (already noted by anikom15)
  • Adjustable h-hold and v-hold knobs on old 70s/80s TVs
  • Reflective screen. Older CRTs are more of a light gray, while later ones have deep black screens.
  • On-screen display for settings. (Isn’t there a way for shaders to detect mouse clicks or button presses, or did I dream this up?)

…and stuff that happens when the CRT is wrecked. These sound like fun to emulate, but I would keep this all in a separate list entirely for obvious reasons.

  • Flashing
  • EEPROM corruption, service menu settings changing randomly for no reason, whole screen going black and white (color killer circuit?), messed up color demodulation, other random screw-ups
  • Contrast so high that high RGB values clamp. THEN, if RGB values go even higher than that, then they start to bleed over to the right. (At least, I think it worked like this, but I’m not sure.)
  • Signs of a worn-out tube in general, like blurriness, I guess.
  • Random uneven burn-in blotches
  • Specific images burned in, like “Windows Server 2000”, an arcade game’s static background, or some “interesting” PC-9801 artwork
  • Dislodged aperture grille, funny rainbows of shame and despair

The whole list could go on for eternity. It would be even longer if we included video signal effects.

Side note: My Panasonic pictures are probably going to have to wait another week, sadly. Time is getting robbed from me.

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#8

Another Excellent contribution! thanks @PlainOldPants your list of additions is enriching

For educational purposes and as a reference for everyone, whether users or developers, and as a contribution to preservation, especially since CRTs are no longer being created.

However, the main goal is to better connect real CRTs with shaders and improve the realism of shaders simulations of CRTs in future

no problem, take your time :slight_smile:

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#9

The first two are due to low-quality flyback, and can happen right after purchase. The third effect occurs when the flyback starts to age.

Due to the nature of CRTs, they all suffer from this, but you may never notice it. I have a TV that is 28 years old and in constant use, and it doesn’t suffer from anything. I had two CRT monitors, a cheap Samsung until very recently, which didn’t suffer from the effect, and a high-end Viewsonic, which started to suffer from it after a couple of years.

Many CRTs had an extra anti-magnetic and anti-radiation film attached to the tube that was very difficult to remove. It is not there to protect the user from an implosion, because it implodes. lol
This film does not produce such an effect, but those apparently flat monitors/TVs do. Although literally, the effect would be called a ‘halo’. In order to create this effect, the glass must be sufficiently separated from the tube.

Glow is the incandescent effect produced by the entire screen when it is illuminated. But Glow is ‘standardized’, just to clarify, I don’t intend to change customs…

Halo <- -> Glow
image

What there are many of, however, are monitors and TVs with glass screens, to make them appear flat, like these ones.

image
image790×388 96.3 KB

If you look closely, you can see the gap.
image

Not an effect as such, but there is a feature of the tubes that would be like the hardScan of TV-out. A high value eliminates the scan lines. I don’t know if any of the ones you mentioned are related to this.

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#10

isnt the “Glow” in the right only seen in camera not eyes?

anyway, it (the left one in the image) has another name, “Halation”, and I guess there are no standard naming in many of these effects, see #02 in the list, it has at least 3 names:- “Phosphor persistence” and “Afterglow” and “Phosphor decay”

#11

“Halation is an optical effect in photography and celluloid film that creates a halo around bright areas of an image”

Actually, yes, these are photography terms.

“Phosphor persistence is the property of a phosphor material to continue emitting light after the excitation source is removed… Phosphor decay refers to the time it takes for the light emitted by a phosphorescent material to diminish.”

It is always good to know how to define concepts, even if they can be used for the same thing. The world of emulation is full of linguistic inconsistencies.

It is true that “digital” cameras have this property, but this is something you can perceive with your own eyes.

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#12

Does halation occur because of glow? At least, on CRTs. There are shaders whose glow effects cause halation, and there are ones whose halation do not cause glow. Or maybe the author bundled everything together and just called it “glow”. I just consider it an umbrella term nowadays.

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#13

Yes, the bright image creates radiation that is reflected in the glass and produces that glowing effect, which is more noticeable in high contrasts.

If it doesn’t have that glass, then it doesn’t produce that effect, but I wouldn’t bet my life on it. There may be CRTs without glass that have that effect. Perhaps the anti-static glass (I said magnetic before, lol) is very far from the tube and produces it, or maybe the tube is of such poor quality that it spreads internally.

Those parameters should be separate, to adapt to other CRTs or ambient lighting; the darker the room, the more noticeable it is.

The glow effect of CRTs can be seen with bezel shaders.

PS: An interesting fact: when the glass is flat, if you look at the CRT from an angle, the glare is shifted by the separation, and you can see the soft reflection of the image, as if repeated.

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#14

There is another effect that affects monochrome monitors: if it is green, the screen turns green, just like the other colors. I don’t know what this is called.

image

#15

maybe the type of phosphor? https://en.wikipedia.org/wiki/Phosphor#Standard_phosphor_types

#16

This is because the phosphors are all green. On a color CRT the background noise creates dark gray and normally you can only see it when you set the brightness too high.

Halation is visible on cameras because cameras have a glass lens. On a normal CRT it should not be visible. When there is a second glass panel, there still shouldn’t be a halation effect because the glass is flat. However, smudges, oil, and dirt on the second glass panel can create a sort of micro-curvature that will create halation (this why dirty glass looks cloudy). If the panel is acrylic instead, it will accumulate scartches and also become cloudy. I believe some arcade cabinets used acrylic panels as a safety measure.

#17

11 (de)convergence and defocus that increase near screen edges

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#18

uhm… warmup time?

My old cab has less contrast and smaller image at power-on time; needs a minute to fully reach intended “levels”

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#19

I remember it was visible, maybe not as obvious as how seen in cameras

BTW, it also did reflected to phosphor strips https://forums.libretro.com/uploads/default/original/3X/7/5/75fb1ce2b99acdd719a4118fd4bee938e0b71428.jpeg

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#20

Yeah, a little bit visible. Very subtle. Also depends how dirty the screen is :slight_smile:

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