[dirGames-L] Frame Rates - weekendoftopic

[Colin Holgate]

>I had an instructor that said they did tests ("they" being the people who do
>tests) and they found that most people can see the flicker in a monitor
>refresh rate below 75Hz, but no flicker is visible at 75+Hz.  "They" also
>found that people don't get headaches from looking at a monitor at 120+Hz.


'They' are being misunderstood. Here's the rules I heard, long ago: 
more than 10 fps seems like something that's animating, over 100 fps 
and you can't tell that it's not continuous. Monitors below 100 Hz 
should have detectable flicker, especially if you avert your eyes 
(I'm guessing that if Roger said something about us being sensitive 
to movement, he knows that it's movement to the side that is most 
noticeable, which indirectly argues for not needing such a high frame 
rate for something in front of you). I'm not sure what the thinking 
is behind the 120 Hz/headaches statement?

Anyway, the misunderstanding part is that there's a big difference 
between flicker and low frame rate animation. A 12 fps cartoon shown 
on TV is being updated 60 times a second (half a frame at a time), 
and so although it's only 12 fps animation (made on 24 fps film by 
the way), it doesn't seem to flicker, not counting the flicker you 
can see by averting your eyes.

You may have noticed that movies seem more solid on TV than in a 
theater, because in a theater the frames are played at 24 fps, and 
perhaps half of the time is spent moving the film along, during which 
there's blackness. On TV the 24 fps is telecine'd into 60 field NTSC, 
and with no film to shuffle along the overall effect works well.

I was disillusioned a bit when I heard that IMAX is 24 fps. I was 
sure that it had a higher frame rate, and that was why it's so solid 
looking. It turns out that the film gets shuffled along from frame to 
frame in maybe 1000th of a second, This means that almost all of the 
time you are seeing an image, and if the image isn't moving too 
quickly, the effect is the same as 1000 fps.