30p vs. 24p

[Tim Dashwood]

I split off all of the DVD 24P questions into this new thread.

Let's stick to the original 24p vs 30p vs 60i aesthetics debate here.

[William Hohauser]

Originally Posted by Steve Mullen

I love the fact you have challanged this "theory" because it should be challanged. BUT, I'm afraid there is a frame-rate boundry between REAL and UNREAL. I'm not sure if it is 24fps or 26fps or 30fp, but I'm convinced it is real. The faster information is presented to our brain, the more REAL it looks. There's no doubt that 50fps looks fairly real.

However, I find it very odd that 24fps -- arrived at supposedly for audio quality -- just happens to be the only NON-REAL frame-rate. Which raises the question: was 24fps actually chosen because it DID work for viewing stories OR have we all learned that 24fps = NON-REAL? (OK -- PAL viewers also accept 25fps.)

Is it really possible that the move from 25 to 30 destroys the ability to be NON-REAL. If so -- what is the dividing line: 26, 27, 28, or 29fps?

I also suspect it is a matter of shutter-speed and shutter-efficiency. Haven't heard of the latter? It's a real term, not mine. But it's time to sleep so I can't explain it now. But, it could be more important than frame-rate.

I would really love to tell which issue of SMPTE journal explains all the perceptual issues regarding frame rate. Unfortunately that was twenty years ago or more, just when HD was starting. It was an excellent issue that deviated from the usual electro-techy stuff and got into a different scientific realm.

It boils down to this: 24 frames is the compromise between audio quality, motion acceptability and film stock economy. Frame rates were experimented with extensively in the silent era. Slower then 18 frames can be classified as Un-real. Music videos use slow frames rates to get a dreamy effect. Peter Jackson uses slow frame rates to give his film monsters (remember the Orcs) a nightmarish quality.

18 to 40 could be classified as "storybook reality". The frame rate is fast enough to convey a sense of reality but slow enough to mask motion and create a super-real storybook setting. 30p still gives a film-like motion quality.

40 to 60 starts to "imitate" reality. NTSC and PAL are really 50 and 60 frames a second. Action that looks fast at 24p looks slower at 60i even though the same amount of time passes. Faster then 60 frames becomes more and more life-like despite claims that the human eye can not detect really fast rates. Douglas Trumbell (sfx for 2001, Bladerunner, ect.) created his 60 frame ShowScan film system expressly for Las Vegas specialty rides where people sit in those motion rigged audience platforms and get shook around while films play 360 around them.
This was the maximum frame rate he could safely get the film to repeatedly run without shredding to bits in the projector. He would have prefered 75 to 100 fps for a more realistic, audience thrilling effect.

I don't remember the exact span of frame rates and now I'm thinking that it may have not been SMPTE journal but the theory is the same.

[David Ziegelheim]

How does shutter speed enter into this. Is there a difference shooting 24p or 30p at 1/48 vs 1/60 vs 1/100 vs 1/500?

[William Hohauser]

Originally Posted by David Ziegelheim

How does shutter speed enter into this. Is there a difference shooting 24p or 30p at 1/48 vs 1/60 vs 1/100 vs 1/500?

Shutter speed is another compromise between mechanics and motion capture. The closer the shutter speed to the actual frame rate the better the illusion of actual motion thru blur. You can experiment yourself and see how faster shutter speeds create an animated look to motion. Animators work hard to learn how to mimic motion blur for a good reason. Faster shutter speeds are helpful for footage you plan to slow down at a later stage.