One very strange assumption here is the notion of 8-bit games running at 30fps. Since most of them were tied to the raster, the vast majority ran at 60fps update speed, with their main game loop running every frame.

The platforms that were purely framebuffer, like the Apple II of ZX spectrum, would be the exceptions. They'd usually run slower but wouldn't be consistent, either. Most weren't double buffered, so the screen partially updated instead of slamming all pixels at once.

I occasionally have similar discussions about this with PCMR folks, where the object is to properly explain why modern 144Hz gaming monitors are superior to 60Hz office monitors, and even more so than 30fps game consoles. My approach is to talk about motion tracking, not retinal persistence. That's also the measurement approach taken by testufo.com.

It helps that I've finally managed to get a 144Hz Freesync monitor of my own...

Let's suppose you have an object (a small ball, perhaps, or a mouse cursor) crossing the screen in 1 second. At 30fps and with 8-bit standard graphics, that's about 10 pixels per frame; on a modern PC at 60fps, it would be about 35 pixels per frame. If you simply stare at the background while that object crosses in front of your eyes, you'll see it occupy those discrete positions in rapid succession; with persistence of vision, you'll perceive multiple copies of the object spaced at regular intervals. This effect actually increases with higher framerates, such that you'll see a larger number of copies of the object, spaced more closely together. Such effects are countered in the movie industry by applying motion blur, so that you see a continuous smear of the object instead of discrete copies.

But let's suppose that the ball is actually a target important to gameplay - an enemy vehicle, perhaps, or the more common use of a mouse cursor - so that you need to track its position by eye and predict its future motion both precisely and accurately. The more accurately you hold the computing gunsight over the MiG, the more of your shots are likely to hit it, even though it's desperately trying to turn out of your line of fire. In such a case, ideally your eye would always point towards the target and you would see a perfectly sharp image of it, with no duplicates and no blur, while the background scenery gets equivalent effects to the above. Applying motion blur to the ball would be counter-productive!

Late-model CRTs approached this ideal when driven at high refresh rates and with a newly rendered frame per refresh, because they had very short persistence phosphors, usually less than a millisecond, and relied on retinal PoV to give the impression of a steady image. That's why 60Hz was slightly flickery on later CRT monitors; TVs often had longer persistence to reduce flicker on typical broadcast signals (60fps NTSC, 50fps PAL). At 75Hz most people stopped noticing the flicker; many monitors could be driven as high as 120Hz at lower resolutions, limited mainly by horizontal scan frequencies and pixel bandwidth, and that was taken advantage of by competitive gamers.

LCD panels work differently; they tend to hold each pixel with a steady colour and require active work to change it. The latest LCD panels can change a pixel very quickly (less than 5ms), but that only occurs in response to a refresh cycle passing it, which even on a 144Hz display happens only every 7ms. So a game console producing 30fps will have the ball in the same place for 33ms at a time, during which it should have moved as much as 70 pixels to simulate smooth motion across the screen in 1 second. If your eyes are trying to follow that, you won't see a sharp (if flickery) image of the ball, but a 70-pixel-long smear that seems to jump rapidly forwards and slide backwards.

At 30fps, a standard 60Hz monitor is refreshing twice per frame. On a CRT, that results in the ball being briefly displayed twice in the same place before moving to the next position. This effect is not noticeable if you stare at the background, but you will see a double image of the ball if you're tracking it - which one is real? Black frame insertion effectively removes the second image, at the cost of increasing flicker and reducing brightness. On an LCD, it effectively reduces the inherent persistence time to 16ms, so the image you see is smeared across only 35 pixels and doesn't jump quite as far within your field of view.

Blur reduction technology for LCDs mostly revolves around strobing the backlight, which is similar in principle to black frame insertion on a CRT. Essentially, the backlight is pulsed very briefly during the vertical blanking interval, when the panel has settled to the contents of a particular frame, thereby simulating the short-persistence phosphor of a CRT and removing the smear on eye-tracked objects. The downside is that it re-introduces flicker to the display - and because it's the whole display pulsing simultaneously, not a scan, it's even more noticeable - so it can only be used safely on high refresh rates, about 75Hz upward. Many monitors with this technology restrict it to 100Hz or higher.

Possibly useful to understand Phi, Beta, and Persistence...
http://mesosyn.com/mental8-14.html

(If there's a hard white ball moving against a hard black background, I'd only want to refer to blur if there are some grey pixels being displayed. Possibly in the community of gamers who discuss such things, my preferred terminology would be non-standard, and only give rise to confusion.)

Well, you could interpret "fps" as "fields per second" where appropriate.

However, a standard CRT-based TV can be driven in non-interlaced mode by removing the half-line shift in the horizontal sync timing; it is then capable of displaying 50 or 60 frames per second with half the vertical resolution. Frequently, 8-bit micros actually did this, or at least behaved as though they had even if they actually left the interlaced timing in. The latter could be seen as a slight shimmer in the vertical position.

Signals from 60fps game consoles and video cameras can also be generating 60 half-frame fields per second, which isn't 30 frames per second. Each frame is only half the visual information for a new 16ms snapshot; the other half is simply lost.

Great example - yes the other half is lost if you take a snapshot of it. But when we look at it, it's maintained on the retina and we are able to assemble it into the full image.

It's interesting that our eyes have what amounts to a variable shutter speed on a camera.

Try looking directly at the City in STARBLITZ (press space to start the game) and then look directly ath the Ship and the City will go from clear to flickery because we can't track it fast enough if we're not focused on it.

Then flip the BW switch (lower left) and look directly at the City and you will see motion blur, our eyes creates visual artifacts that can't be photographed.

http://javatari.org/?ROM=http://relationalframework.com/StarBlitz_double_fun.bin