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I am wondering what were the color shades and brightness of the text appearing on classic monochrome terminals?

If I were to recreate approximately the green-text-on-black-screen or amber-text-on-black-screen in the user-interface of an app on modern computers, what color should I use for such text?

➥ Any idea of the RGB values of such text? Brightness?

Photographs of computer stations from that era seem to have very poor color fidelity. So I am left wondering… and asking.

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    Relevant: superuser.com/questions/361297/… – Joe Nov 21 at 4:29
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    Though there’s not quite the equivalent to CRT brightness and visible scan lines... – Joe Nov 21 at 4:29
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    Brightness was often controlled by a potentiometer: you could set brightness anywhere from completely off to glowing background with unreadable bright blobs of text – scruss Nov 21 at 10:58
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    NOTE: The green lines in Stephen Kitt's answer look brighter and yellower than anything that I remember. I don't know whether the image that he posted contains a color space profile, but it wouldn't matter for me anyway because I have not calibrated my computer monitor for any particular color space profile. Without that profile and with no calibration, there's no reason I should expect the colors that I see on my monitor to be any better than a rough approximation of the colors that the creator of that image saw on their monitor when they made it. – Solomon Slow Nov 21 at 16:05
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    @Vorsprung That's because there was some research showing that green or amber was better - less eye-strain, etc. I actually wrote a short paper on that (really a review, no original research) in college for Junior English Technical Writing. – manassehkatz-Reinstate Monica Nov 22 at 14:58
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Based on the phosphors used for green and amber screens, this answer on Super User gives the following values:

green/amber RGB values

i.e. #FFB000 for dark amber, #FFCC00 for light amber, and variations around #33FF33 or #66FF66 for green.

Additionally, colours vary with brightness adjustments and with the age of the phosphors.

It should be pointed out that reproduction of colours isn't consistent across current generation monitors. Thus, even if the values in this answer are used, what each person will see on their screen will be slightly different than what another person will see with different hardware. For applications where accurate color reproduction is important, there are monitors/software/systems/test hardware which can be used to calibrate the colour gamut of the monitor in order to more accurately reproduce colours.

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    I still tend to setup my IDE this way as my eyes get sore from the default black-on-white-background... – tum_ Nov 21 at 7:48
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    I remember how much more I liked amber than green text on black, back in the monochrome monitor days. I'm not sure why, but amber seemed to have better contrast and was not as annoying. – user8356 Nov 21 at 19:23
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    As an aside, you could also get red monochrome tubes, which were used in marine and other applications where operators needed to preserve their night vision. – Rich Nov 21 at 19:58
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    Am I misremembering, or were there light blue monitors as well? I seem to remember light blue text on a Data General monitor around 1985, but maybe it was just the monitor itself that was blue? – LAK Nov 21 at 22:12
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    The above colors look pretty close to what I remember, but I stared at it awhile 'cause it wasn't quite right. Then I realized - it is way too sharp. You need to mix this answer with the one below for the full effect (I feel these colors are good for amber and green). Most green-screen monitors were 640x480 at best in early days. – Robb Sadler Nov 22 at 16:10
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If your aim is to recreate more closely the effect of an old CRT (at the expense of readability), whatever color you choose based on the previous answer, you should consider using a very bright (almost white) color for the text itself, and then using the chosen color as a glowing neon-like effect around the outline of the text.

For example, here is what you can obtain based on the #00FF66 color:

Simulation of phosphor bleed

As a reference, here is the CSS style that corresponds to the above effect:

font-size: 30px;
color: #f0fff8; /* almost white */
text-shadow: 0 0 3px #80ffc0, 0 0 10px #00ff66, 0 0 20px #00ff66, 0 0 30px #00ff66;

Using multiple shadows with increasing radius makes for a better effect. Also note the first, small radius (3px) shadow is also chosen in a color closer to white.

And the font I used is Glass TTY VT220 (cool font by the way, and public domain).

Here is a real image of an old computer (I don't even know what it is, it looks like a french minitel) where you can see the text is actually very bright, and the general appearance looks very close from what I recreated above (maybe more cyan-ish than green-ish, but we clearly see the glow):

Computer showing phosphor bleed effect

This is also how graphs appeared on old analog oscilloscopes.

  • That is a nifty effect! I asked a Question on Stack Overflow where you can provide this info for CSS programmers to find. – Basil Bourque Nov 21 at 22:29
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    It's probably worth noting that, while the glow effect is indeed real to some extent, it tends to be exaggerated in photographs like yours above. It's mostly because the white (or amber or green, as it may be) pixels on a screen tend to be a lot brighter than, say, the plastic parts surrounding the screen, and because cameras have a narrower dynamic range than that human eye and can't correctly expose for both at the same time. So if the photo is exposed so that things around the screen look well lit, the bright parts of the screen itself will be overexposed and any glare will be amplified. – Ilmari Karonen Nov 22 at 7:10
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    The example display you're showing was using a "white" phosphor, one that had a blueish tinge to it as was common back then for black and white displays. Amber and green displays were a reaction to that, offering a purer colour that was supposed to be sharper and easier to read. They didn't look bright white with a green/amber halo like your first picture because they're weren't using phosphors that were supposed to be white. – Ross Ridge Nov 22 at 7:16
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    It "looks" like an old French Minitel but the keyboard had more special functions keys and of course was an Azerty layout (the one in the picture is a Qwerty...). – Hoki Nov 22 at 10:58
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    A bit of googling brings up the very similar Philips HCS80, which is indeed related to the french Minitel. This one's UI is in italian. – Quentin Nov 22 at 13:50
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I dimly recall these two specific hue frequencies were picked because the human eye focuses them the most accurately. Other colors would focus in front of or behind the retina.

A modern RGB green is pretty close to the right color of green, I believe so can be used as is.

Recreating the old amber on an RGB screen does not work because it generates not a single easy-to-focus amber wavelength, but two different wavelengths, one of green and one of red, that definitely do not focus at the same distance, and further won't be bent the same by the glasses of an eyeglass wearer, thus separating into separate red and green characters. You can create a color that seems to be the same, if you want, but it will lack the key property of the original of being easy on the eyes.

Outside the scope of your question, but since RGB's green channel is so sharply-focused on the retina, you can make equally easy-to-focus text with any foreground you want. The background should simply use the same R and B channels, and have the G channel be 0 or maximum, whichever is farther from the foreground's G channel.

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    As a human with eyes, I can confirm that I'm easily able to focus on objects of any color, not just green and amber objects. You might be thinking of the fact that it's easier to focus the CRT itself if a single phosphor material is used, compared to mixing phosphors. – Sneftel Nov 22 at 12:10
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    I've searched without success for P1 and P3 phosphor spectral curves. I'm not sure how narrow their emission is. Unlike laser emitters, many phosphors have a broader emission spectrum. Was P3 really a narrowband emitter peaking at yellow/orange, or did it contain significant green and red energy? (I've got a P3 monitor boxed up in the garage, wonder if it would power up, and if I could find something to drive it...) – jeffB Nov 22 at 14:03
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    @Sneftel Your brain does the correction and the whole point is to relieve this duty: physics.stackexchange.com/questions/12602/… – Agent_L Nov 22 at 14:16
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    @Sneftel focus in a CRT has nothing whatsoever to do with the phosphor(s). – rackandboneman Nov 22 at 16:36
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    @jeffB: Even if it was somewhat broader, a single peak will focus much better than two separate peaks. It shows up as a slight to moderate blur with fringing rather than as offset copies of the shape in different colors. I say this as someone plagued by extreme chromatic aberration. – R.. Nov 23 at 2:32
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I have never seen an amber display, but I have seen a whole lot of different hues of green - yellow-ish, blue-ish, cyan-ish, white-ish, deep green, probably whatever the tube maker had left for the mix. And I am even not sure that the "deep green" I remember is at all possible to represent by all-positive RGB values.

An important aspect to represent is the phosphor persistence - the pixels fading in slow fashion (1/10..1/2s) after being illuminated. Some of them even faded to warmer color before going completely dark.

  • I guess amber covers quite well, what you call 'yellow-ish'. I would somehow doubt that 'whatever was left'' was used, as they required specific processes, some rather costly. Emitting light also couldn't fade to warmer colour, as colour is fix defined by the energy levels of the material used. It just got less. – Raffzahn Nov 22 at 18:00
  • I mean green that is yellow-ish. Amber is a different thing, in RGB it contains way more red than green. – fraxinus Nov 22 at 18:05
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    @Raffzahn sure it could, if you had a bluer emitter with a short decay and a redder emitter with a longer decay. I don't have my search results from earlier in the day, but I remember one of the green phosphor formulas had two distinct emission peaks, and I believe it was composed of two different emitters. I believe one of the use cases was for radar in the presence of jitter-inducing jamming; adding a gel filter knocked out the fast-response image, leaving the slower "averaged" long-decay image. For sharper images in the absence of jamming, you'd filter in the opposite direction. – jeffB Nov 23 at 5:31
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Green screens are still used today, in bank environments IBM iSeries systems are still popular. These terminals are not monochrome anymore, are software based (emulated), but basically they are just old green screens. If you do image search for 'iseries green screen' you can find this colorfull example:

iSeries green screen

Now if I look into terminal settings, green color is RGB 00FF00. I do not see amber color, but there is mustard color RGB A0A000

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    The point of the question is to determine how to reproduce the colour produced by the phosphors coating old monochrome screens; the screen you’re showing is a multi-colour mono-spaced text screen, which just happens to be showing a lot of green text... – Stephen Kitt Nov 24 at 10:42
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    This is software emulation, not an actual display. They just picked some default values for the settings. – Thorbjørn Ravn Andersen Nov 26 at 6:21
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It's kind of an impossible question, since (as others have mentioned), it is entirely dependent on the monitor that you are trying to recreate it on. In fact, I have two identical monitors, HP Compaq LA2306x, side-by-side, with identical settings. If I drag any image/window/text to where I can see part on one monitor and part on the other, there is a clear difference in appearance, even if viewed from the same angle. One is older than the other, so maybe that is the reason, but that just points out another variable to color perception. One uses Thunderbolt conversion to VGA, and the other uses HDMI converted to DisplayPort, so that could be the cause, but again, that only points out more variables.

  • It is basically impossible to answer precisely, because "classic monochrome terminals" and "modern computers" are both vague categories, with a lot of variance within each category. And even if you could nail down exactly which classic monochrome terminal and which modern computer, there would still be variances in display. So, make a stab at it and call it good. No one can really tell you you're wrong :) – CTrese Nov 26 at 16:25
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    Mind to inccoperate additional thoughts into your Answer? Commenting it is less than ideal. – Raffzahn Nov 26 at 16:41

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