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Movies look reasonably smooth at 24 frames per second; unless the screen is huge and you use your peripheral vision, you usually can't see each frame individually. This has lead to a large amount of textbooks claiming that the visual response time of the retina is slower than 1/24 seconds.

However, games at 24 frames per second absolutely suck. The motion is so choppy it is unplayable. For a game, you seem to need at least 40 frames per second, and even at that rate you still see individual frames if the objects are moving quickly.

Why is this so? Is this related to the fact that movies have motion blur due to a non-zero shutter speed? Is "jerkiness" mostly perceived in terms of "gap between object in frame 1 and frame 2" rather than visual response time (the gap is smaller in films due to blurred objects "connecting" across frames)? If so, doesn't this prove that our visual response time is much faster than 1/24 seconds?

To make the question more precise: is this response determined by physical mechanisms, such as the relaxation times of pigments in the eye or the firing times of neurons? If so, which ones? Or is it mostly due some sort of postprocessing done by the brain, i.e. more to do with the cognitive than the physical side of perception?

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closed as off-topic by dmckee Dec 3 '13 at 20:52

  • This question does not appear to be about physics within the scope defined in the help center.
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Frankly, this is not a physics question. It is purely a questions about the human visual system that does not even pretend to be about physics anywhere. –  dmckee Dec 3 '13 at 20:52
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@dmckee Can you suggest an alternative venue for this excellent question? In the absence of one, I would argue that this is also a question about the capabilities of our own optical equipment. Or is any question about the physical response of human senses off-topic? –  Emilio Pisanty Dec 3 '13 at 21:02
    
He could try biology or cognitive sciences, but I don't know enough about either one to suggest migration myself. We have tended to allow questions that can be answered at the level of "the pigments in the eye respond to photons of ### wavelengths" as having some physics content. –  dmckee Dec 3 '13 at 21:09
    
I think this question would much more fit to games-related SE site, or maybe even to a programmers one (general, not Stack Overflow). –  trejder Dec 3 '13 at 21:25
    
@dmckee So if this had an answer along the lines of "the relaxation times for the pigments in the eye are of the order of ..." it wouldn't be a physics question? –  Emilio Pisanty Dec 4 '13 at 16:24

1 Answer 1

Movies don't get away with 24 frames per second. In old 35mm film movies, 24 new frames are shown every second, but each frame is actually flashed onto the screen twice. The flicker is therefore at 48 Hz, even though the data update rate is 24 Hz.

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This is totally the wrong answer. I'm not asking about flicker on CRTs etc. I'm asking about frame rates on flickerless media such as LCDs and modern projectors. Data update rate is what I'm interested in; on modern screens the flicker is infinity Hz but with a too low data update rate you get a jerky feeling. My question is about why this minimum rate is so much lower for movies than for games. –  user54609 Dec 4 '13 at 16:28

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