Strictly speaking, because the signal is continuous, analog video doesn't really have horizontal resolution, does it?
CRTs additionally impose their own limit on how sharp the picture can get horizontally. Confusingly, these are called "television lines", even though you'd think that refers to the horizontal scanlines that do discretely divide up the picture vertically. Color CRTs further limit the amount of color resolution independent of luminance resolution, and how they do that depends on what specific phosphor pattern they use, how they separate electrons from each color gun, etc.
[0] And one that's just as misleading as sample-and-hold diagrams of digital audio that make people go out and buy really expensive DACs for reproducing ultrasonics they can't hear
The colour was created by different phosphors on the inside of the screen, there was nothing different about the electron beams. The number and pitch, the resolution, of these different phosphor dots determined the resolution of the screen.
The shadow masking was to prevent the beam for, say, the red phosphors sweeping blue/green subpixels when moving from one pixel to another, since it wasn't practical to turn the beam off and then back on once the steering coils had been changed. Steering was continuous, so without shadowmasks, you would illuminate on the neighbour subpixels you pass on the way.
You could have done it all with a single beam, if you really wanted, but it's not very practical - you'd need to sweep slower since you could only illuminate 1 subpixel at a time, it'd take much longer to to steer, illuminate at the right level, and move to the next with the right beam power selected.
I think he described exactly what you did (in fewer words) in the second half of his post. ("Your typical color TV ..."
The first half discusses that some projection screens had 3 different tubes. ("Very few broadcast TVs ...")
Either that or he edited his post.
> Your typical color TV effectively created "pixels" by their use of shadow masks and three separate beams.
It's true that almost all colour TVs are pixelated and have shadow masks and three separate beams, but it's got the cause and consequence the wrong way around.
The pixels are created by the phosphor dots, not the mask/tube design. It's possible to use this design without three tubes or the screen, strictly, but a consequence of this design suggests the optional addition of a shadow mask and additional tubes as a natural, later progression for improved performance.
Without shadow masks or an aperture grille seems pretty dang hard. Even ignoring the alignment concerns, it requires a much, much higher bandwidth.
The shadow mask and aperture grille approaches were the only approaches that ever really worked for color CRTs.
Phosphors and some kind of masking is how you make different colors on a single tube. Indeed, the shadow mask or aperture grille was offset 3 times and used to etch for the phosphor coatings in most manufacturing processes.
> l addition of a shadow mask and additional tubes as a natural, later progression for improved performance.
There's just one tube-- multiple guns/beams, though.
Let's say you're displaying a 640x480 screen on a TV. Your chroma information is sampled from an area about 2.1 pixels wide. So even if the signal is continuous, your color information is the result of sampling a boxed area centered on that pixel.
And because you don't want the wave pattern to be displayed as luma, you also take the average luma of that area. Now you have a blurred fat color pixel, but it can be positioned anywhere continuously.
Furthermore, even when using NTSC video timings, the 3.58 MHz subcarrier is specific to transmission of composite video (carrying brightness and color combined in the same signal). A DVD player for instance with a component or SVideo output produces NTSC timing but there is no subcarrier because the color signal is discrete.
To the number of horizontal pixels is essentially limitless (if you ignore the bandwidth limit and the CRT scan raster) while the number of vertical pixels/lines is always discrete.