Interesting post. From my work on 1980s micros that used CRT TVs for display, the phosphor response described here seems to be a bit oversimplified.
In my purely subjective experience, rise time seems to be shorter than fall time - pixels will usually be visibly blurred on the trailing (right) edge, but sharper on the leading (left) edge. Another thing I noticed is that a longer horizontal row of pixels will leave a longer decay on the trailing edge than a single pixel. For example, the Ts will usually have their horizontal line visibly stretched on the trailing edge, even when the vertical line seemed sharp.
Of course, purpose-built terminals might have used different phosphors than cheap TVs of the time. It might also have to do with video amp bandwidth, or something else electrical.
Without disagreeing with you, the diagrams from the linked page are pretty much reproductions of the ones from an official VT100 technical manual, https://vt100.net/docs/vt100-tm/
It appears to me that the rise/fall graphs are just graphs of ideal RC networks, while the whole true CRT system will have lots of other factors such as inductance going on.
When it comes to comparing what you might recall of CRT TVs and 80s micros to what a dedicated monochrome CRT would show, well, the dedicated CRT was much better and sharper, particularly if your color display technology involved a "composite" system like NTSC or PAL, where horizontal luminance (Y) bandwidth was SEVERELY limited to "make room for" the color information (I/Q).
To get an idea of how much Composite video encoding degraded picture information, take a look at modern videos of "RGB-modded" classic consoles such as https://www.youtube.com/watch?v=kpdpAxzjmA8 -- As far as I understand from the video explanation, both signals are video-captured, so this is not a "CRT effect", it's a "composite video effect" that makes the right-side image so smeared. There's also the palette difference, but that's more a matter of preference.
I'm not sure this is a consequence of the phosphors. It looks to me like this is an effect of how quickly the electron gun turns on and off. I would expect the horizontal sweep rate to be unaffected by whether pixels are supposed to be on or off, so the blurring at the left edge is determined by how quickly the beam ramps up to full current when turned on, and the blurring at the right edge is determined by how quickly the beam current is switched off.
The slow decay of the phosphors is on an entirely different timescale: more on the order of the time taken to refresh the entire screen, rather than the time taken for the e-beam to sweep across a single pixel. The asymmetry in the phosphor's activation vs decay is vastly greater than the asymmetry in the electron gun's switching on and off.
TVs had their sub-pixels arranged differently to the CRTs on many computer displays. This lead to a lot of “fuzzing” beyond that phosphor response when computers were hooked up to TVs.
A classic example of this is when you play retro consoles on an authentic household TV verses VGA.
Some systems actually used this technique as an additional rendering trick. For example having a foreground sprite where every other pixel was invisible and those pixels would be blurred by the TV to give a more authentic looking transparency effect.
(OP here). There are actually no pixels on a monochrome screen, rather, there's just an even phosphor coating. What we may assume to be a pixel is just an effect of the signal generating the pattern. Color TV changed this radically, as there was now a shadow mask and (usually) vertical strips of phosphor. However, pixels were still determined rather by the generating signal than by the subpixels of the shadow mask. (So a pixel may illuminate any number of phosphor regions exposed to the cathode ray at this very moment.) Moreover, a TV usually included some kind of sharpening circuitry, which was more tuned to moving images and didn't perform that well with static content. And, of course, various color systems (NTSC/PAL/SECAM) generated different effects and artefacts of their own.
Yes I know. My point was the arrangement of the RGB dots that made up a region was different on CRT TVs to that of colour CRT monitors (ignoring the old terminals for now because they’re a different era of device entirely). That did have an effect on the sharpness of the image.
What I didn’t mention but is also worth noting is the quality of the input signal would have mattered as well. 8bit micro monitors, even in the 80s, generally took RGB input. Whereas any micro that output to a TV would often do so via a the antenna, ie the computer would have to be tuned in like a TV station. This means you then have all of your prime colour “wires” as well as audio mixed into one analogue signal. Which obviously degrades the overall image and sound quality. Plus TV tuning isn’t nearly as precise as having a proper dedicated cable. The devices from the 80s (and 90s) which supported both ANT and RGB really show just how significant the difference between the two is. Which is also why you often see a lot of retro gear being sold as “RGB modded”.
Basically what I’m saying is comparing a budget micro on an 80s home TV to a raster CRT terminal is rather pointless. Different tech, different target audience, different eras.
My post wasn't meant as a critique, rather as an expansion on yours. We are so used to thinking in pixels that we often forget there weren't any hardware pixels in B&W. It was whatever the circuitry could produce. You observations on color TV are certainly right. From what I remember, the most obvious distortion came from the sharpening (which is seldom mentioned today), resulting in hard, double vertical edges. This may have been more prominent in PAL than NTSC. – How I did long for a legit RGB monitor, but it was just a color TV for my C64 anyway. :-)
In my purely subjective experience, rise time seems to be shorter than fall time - pixels will usually be visibly blurred on the trailing (right) edge, but sharper on the leading (left) edge. Another thing I noticed is that a longer horizontal row of pixels will leave a longer decay on the trailing edge than a single pixel. For example, the Ts will usually have their horizontal line visibly stretched on the trailing edge, even when the vertical line seemed sharp.
Of course, purpose-built terminals might have used different phosphors than cheap TVs of the time. It might also have to do with video amp bandwidth, or something else electrical.