3 ms·

It is easy to prove that humans can perceive more than 60 frames per second: wave your hand in front of a fluorescent light. They flicker at the same speed as y

by po 17y ago

It is easy to prove that humans can perceive more than 60 frames per second: wave your hand in front of a fluorescent light. They flicker at the same speed as your electricity (in the US it's 60Hz) and you can easily see the motion break down.

notaddicted 17y ago
They flicker at 120, because the top and bottom of the sine wave both "flick".
csbrooks 17y ago
Side note: If you have florescent lighting running at 60hz, and a UK tv running at 50hz, you get a horrendous flicker effect on the tv. (I got this working on the EU version of a console game, in the US, on an imported UK tv.)
ajross 17y ago
That's not "perceiving" at 60Hz though. The eye is seeing an integrated image, which happens to be of several "frames" of your hand lit mixed with gaps of darkness. Effectively, you're seeing multiple strobes "at the same time". You do get aliasing effects with strong strobing though, where your eyes can see beating patterns in the image intensity. That's why some people get eye strain looking at 60Hz displays; moving to ~70Hz or so generally fixes it. But again, our visual systems do not have the ability to distinguish between individual events separated by 1/60th of a second. We just can't do it, and trying to animate at that speed is purely wasted effort.
- csbrooks 17y ago
  >But again, our visual systems do not have the ability to distinguish between individual events separated by 1/60th of a second. We just can't do it, and trying to animate at that speed is purely wasted effort. And yet, there's a very clear perceivable difference between a game running at 30hz and 60hz. How does that work?
  - ajross 17y ago
    I don't buy it. Until someone shows me a real study (or even a demo where I can verify the frame rate and see the effect for myself), I'm not going to believe this "effect" exists. Almost certainly, you're not seeing a 30Hz game. You're seeing a game running at 30Hz typically and being annoyed by a handful of frames that take longer than ~100ms. It's the outliers that are doing it, not the frame rate.
    - DarkShikari 17y ago
      Then watch a 60fps video. Then decimate it to 30fps, and watch that. Or will you claim that there are "outliers" in a constant framerate video, too? The visual difference is so significant that television broadcasters have kept interlacing solely for the greater temporal resolution, despite the tens of billions of dollars in inefficiencies that the legacy technology creates.
      - ajross 17y ago
        If the decimation does anything but average frames, then it's a lossy process and of course there will be detectable differences. And if it does average frames, it's susceptible to the aliasing issues I mentioned above (lighning flashes become gray blurs, etc...) The question was if there's a single game (or video) you can point me to that (1) has a solid 30Hz frame rate and (2) looks perceptibly "not smooth" for some obvious definition thereof.
        DarkShikari 17y ago
        Sure. Here, I'll give an example that doesn't even rely on high motion, flashing, or other such tricks: a simple video game clip. This particular game engine has its display locked to 60fps: the in-game time between two frames is absolutely constant, so even if your computer is too slow to display in realtime, it will simply output frames slower. As a result, the FRAPS'd capture of the game is a perfect smooth 60fps no matter what. Additionally, it doesn't have any single-frame effects that would be visually aliased (e.g. lightning), nor does it have any sort of motion blur. http://mirror05.x264.nl/Dark/testfps1.mkv http://mirror05.x264.nl/Dark/testfps1.mkv http://mirror05.x264.nl/Dark/testfps2.mkv http://mirror05.x264.nl/Dark/testfps2.mkv Don't look at the filesizes (obviously, 60fps will be larger), and don't go checking the file info or whatever. Just play them in your favorite media player. I'm pretty sure you'll be able to tell which is 60fps.
- fhars 17y ago
  Your conclusion is a non sequitur. While people cannot discern individual events a 60Hz, most will perceive a CRT monitor as slightly but disconcertingly flickering, an effect that only vanishes at 70Hz or more (I once had a co-worker who didn't notice that 60Hz flicker and opted for more pixels over higher frequency in his XF86Config, nobody else could look at his monitor for extended periods of time...). So there definitely is some room for quality improvements above 30Hz, but the amount depends on the viewer and the technology (flat screens do not flicker even at 60Hz, and it is almost always preferable if you animation frame rate is the same as you video refresh rate [edit: or an integer fraction thereof. From which premise we can mathematically prove that there is only one acceptable frame rate for TV sets: the least common multiple of 30Hz (NTSC video), 25Hz (PAL and SECAM video) and 24Hz (movies), which happens to be 600Hz. Way to go, my dear marketing departments.] ).
fhars 17y ago
That is not percieving, that is aliasing and conclusively demonstrates that you cannot percieve 60fps. If you could, you would see only one image, not a superposition of several illumination states.

by po 17y ago

notaddicted 17y ago

They flicker at 120, because the top and bottom of the sine wave both "flick".

csbrooks 17y ago

Side note: If you have florescent lighting running at 60hz, and a UK tv running at 50hz, you get a horrendous flicker effect on the tv. (I got this working on the EU version of a console game, in the US, on an imported UK tv.)

ajross 17y ago

That's not "perceiving" at 60Hz though. The eye is seeing an integrated image, which happens to be of several "frames" of your hand lit mixed with gaps of darkness. Effectively, you're seeing multiple strobes "at the same time". You do get aliasing effects with strong strobing though, where your eyes can see beating patterns in the image intensity. That's why some people get eye strain looking at 60Hz displays; moving to ~70Hz or so generally fixes it. But again, our visual systems do not have the ability to distinguish between individual events separated by 1/60th of a second. We just can't do it, and trying to animate at that speed is purely wasted effort.

csbrooks 17y ago
>But again, our visual systems do not have the ability to distinguish between individual events separated by 1/60th of a second. We just can't do it, and trying to animate at that speed is purely wasted effort. And yet, there's a very clear perceivable difference between a game running at 30hz and 60hz. How does that work?
- ajross 17y ago
  I don't buy it. Until someone shows me a real study (or even a demo where I can verify the frame rate and see the effect for myself), I'm not going to believe this "effect" exists. Almost certainly, you're not seeing a 30Hz game. You're seeing a game running at 30Hz typically and being annoyed by a handful of frames that take longer than ~100ms. It's the outliers that are doing it, not the frame rate.
  - DarkShikari 17y ago
    Then watch a 60fps video. Then decimate it to 30fps, and watch that. Or will you claim that there are "outliers" in a constant framerate video, too? The visual difference is so significant that television broadcasters have kept interlacing solely for the greater temporal resolution, despite the tens of billions of dollars in inefficiencies that the legacy technology creates.
    - ajross 17y ago
      If the decimation does anything but average frames, then it's a lossy process and of course there will be detectable differences. And if it does average frames, it's susceptible to the aliasing issues I mentioned above (lighning flashes become gray blurs, etc...) The question was if there's a single game (or video) you can point me to that (1) has a solid 30Hz frame rate and (2) looks perceptibly "not smooth" for some obvious definition thereof.
      - DarkShikari 17y ago
        Sure. Here, I'll give an example that doesn't even rely on high motion, flashing, or other such tricks: a simple video game clip. This particular game engine has its display locked to 60fps: the in-game time between two frames is absolutely constant, so even if your computer is too slow to display in realtime, it will simply output frames slower. As a result, the FRAPS'd capture of the game is a perfect smooth 60fps no matter what. Additionally, it doesn't have any single-frame effects that would be visually aliased (e.g. lightning), nor does it have any sort of motion blur. http://mirror05.x264.nl/Dark/testfps1.mkv http://mirror05.x264.nl/Dark/testfps1.mkv http://mirror05.x264.nl/Dark/testfps2.mkv http://mirror05.x264.nl/Dark/testfps2.mkv Don't look at the filesizes (obviously, 60fps will be larger), and don't go checking the file info or whatever. Just play them in your favorite media player. I'm pretty sure you'll be able to tell which is 60fps.
fhars 17y ago
Your conclusion is a non sequitur. While people cannot discern individual events a 60Hz, most will perceive a CRT monitor as slightly but disconcertingly flickering, an effect that only vanishes at 70Hz or more (I once had a co-worker who didn't notice that 60Hz flicker and opted for more pixels over higher frequency in his XF86Config, nobody else could look at his monitor for extended periods of time...). So there definitely is some room for quality improvements above 30Hz, but the amount depends on the viewer and the technology (flat screens do not flicker even at 60Hz, and it is almost always preferable if you animation frame rate is the same as you video refresh rate [edit: or an integer fraction thereof. From which premise we can mathematically prove that there is only one acceptable frame rate for TV sets: the least common multiple of 30Hz (NTSC video), 25Hz (PAL and SECAM video) and 24Hz (movies), which happens to be 600Hz. Way to go, my dear marketing departments.] ).

fhars 17y ago

That is not percieving, that is aliasing and conclusively demonstrates that you cannot percieve 60fps. If you could, you would see only one image, not a superposition of several illumination states.