Why 24hz?

[beachball8]

Why is there a preference for 24Hz? Isn't faster better (eg the native 60Hz)?

someone tried to explain this to me this morning but I am confused. either he doesn't know what he's talking about or i'm dense.

 

[Macadamianut]

From my understanding 24hz(frames per second) is the slowest speed you can get while maintaining a smooth picture. Slowest speed = cheapest costs to make a movie. Its all about money.

 

[erikt]

Movies are filmed at 24fps so if you display a 24fps film on a 60Hz display, you get judder due to 3:2 pull-down (basically, taking two frames of the film, the 1st is displayed 3 times and the 2nd is displayed twice to multiply 24Hz up to 60Hz). If you display at 24Hz movies look good, but 60Hz video material (for e.g. a lot of DVD bonus material) doesn't work.
ET

 

[damnskippy]

Of course this is a film thing and the digital captures are not limited in this way but have to be compatible.

I would like to see them move to shooting everything at 60 fps

 

[beachball8]

And so TV's that are refreshing at 100Hz or 200Hz are actually moving away from the ideal rate of 24Hz???

What kind of pulldown does it do for a 100Hz/200Hz TV?

 

[erikt]

120Hz is great as it's a multiple both of 24Hz and 60Hz. I don't know of any reason for 240Hz and I haven't heard of 100Hz/200Hz (though I don't really keep up with all that).
ET

 

[damnskippy]

I really don't like the 240Hz and don't much care for 120Hz. It is just too perfect as far as motion goes and it looks fake to me. I mean in real life it does not look that good, especially 240Hz.

 

[DigiMagic]

120Hz is great as it's a multiple both of 24Hz and 60Hz. I don't know of any reason for 240Hz and I haven't heard of 100Hz/200Hz (though I don't really keep up with all that).
ET

100Hz was popular in Europe because 50Hz interlaced CRT displays flickered way too much for comfortable viewing (IMHO). I guess 200Hz is an improvement over that.

24Hz is converted into 100Hz by speeding it up few percent to get 25Hz (as a side effect, some viewers notice "chipmunk" voices), then displaying odd-even-odd-even frames (on interlaced display), or 4 progressive frames on non-interlaced.

 

[Haplo]

It's all about the frames per second of the source compared to the refresh rate of your display device.

So, 23.976fps or 24fps will look best when the refresh rate has an even multiple of that value, so 24Hz, 48Hz, 72Hz and so forth. The 23.976fps is very close to 24fps so with e.g. Reclock that little difference isn't a big deal.
If your display device can do it then a multiple of 23.976 is even more accurate, e.g. CRT monitors and projectors can do this.

Likewise if the source is 25fps as in most PAL DVD's (BD's are usually 23.976 or 24fps even in PAL-land) then a multiple of 25 is often more accurate to avoid microstutters. 50Hz or 75Hz and so forth.

If it's NTSC material that have already had the 3:2 pulldown process done on the source then it's a multiple of 29.97 or 30 that is more accurate. Bonus material or were the source was simple done direct to TV in NTSC land.

Regarding "chipmunk" voices on PAL releases, in movies with a bigger budget when released in PAL-land the sound is pitch-corrected. So basicly turning the pitch down by 4% since that is the speedup from 24->25fps.

 

[James]

Regarding "chipmunk" voices on PAL releases, in movies with a bigger budget when released in PAL-land the sound is pitch-corrected.

Name a single one, which isn't "Lord of the Rings".

 

[Haplo]

I got the impression that it was done on the bigger releases but maybe I'm wrong. On the other hand I haven't A/B'ed it so maybe it just a rare few that is actually "fixed".