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PAL vs NTSC and frame rates

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Mike Tyler
PAL vs NTSC and frame rates
on Apr 6, 2017 at 8:08:20 am

Hey people,

so after a recent shoot with my Sony a6000 a few questions came to my mind...

I've shot at 50 fps PAL at 1/60 shutter speed... (now I know it should've been 1/100th - but to me, the video looks normal anyway).
just did some research and realised it's probably not optimal to shoot at above 25 fps when I don't intend to slow down the footage.

Now my question is.. if I am shooting only with natural light, would 25 fps PAL or 24 fps NTSC be 'better' ?

I honestly can't think of how this would make a difference.. that's why I am asking you more technically experienced guys.

I also mention the natural light, as I've read about issues with flickering when using NTSC in Europe / PAL in USA with artificial lighting..


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Todd Terry
Re: PAL vs NTSC and frame rates
on Apr 6, 2017 at 3:10:15 pm

[Mike Tyler] "it's probably not optimal to shoot at above 25 fps when I don't intend to slow down the footage."

Correct, you should really not overcrank unless you intend (or think that it is fairly likely that you will) end up slo-mo'ing the footage. A lot of people say "Why?... I can just play it all at 'normal' speed in post, and then if I need slow motion, then I've got it." It is because when you use your overcranked footage at "normal" speed, then you are effectively shooting at too-high a shutter speed. If you are in the 24fps world and you shoot 24fps footage, your optimal shutter speed will be 1/48th of a second. The easy formula is "One over twice the frame rate." This emulates a 180° shutter in a film camera, and gives you the amount of motion blur that you need for your brain to interpret the footage as smooth. But... lets say you overcranked by 2x, and shot at 48fps. Then you likely would have had a shutter speed of 1/96th of a second. For easy math, let's say 1/100th. Well, when you use that footage as slow-mo, everything looks great. But if you speed up the footage 2x so that you have normal non-slow mo speed, the speed looks right but it is as if you shot 24fps footage but with a 1/100th shutter speed... which is much higher than normal. You'll have half as much motion blur compared to normal footage, and your motion might appear jittery and choppy with sort of a staccato look. Now, you MIGHT not see it that much (except with very fast motion) if you are only overcranking 2x, but higher than that and you'll definitely see it.

[Mike Tyler] " if I am shooting only with natural light, would 25 fps PAL or 24 fps NTSC be 'better' ?"

You'll typically want to do a project in whatever the native framerate is in the part of the world that you are... or will be distributing. In the US films are invariably shot at 24fps, and converted to 60i for our NTSC television systems (3:2 pulldown). In the UK and parts of Europe the PAL format of 25fps is the norm, so you'd likely want to shoot 25fps there.

[Mike Tyler] "I've read about issues with flickering when using NTSC in Europe / PAL in USA with artificial lighting.."

That can be true, with non-continuous sources like fluorescents, HMIs, etc. But flickering is just as much (if not moreso) a function of shutter speed as it is frame rate. Usually cameras in clearscan mode can dial in a flicker-free exact shutter speed (which isn't measured in fractions of a second, but rather in hertz) that eliminates that. If not, then it is acceptable to shoot in the frame rate that is normal for whatever country you are in. Then, you can conform to your "usual" frame rate in post. If you go from 24fps to 25fps (or vice versa), it's only a 4% difference so visually that is usually not noticeable (you might have to make a slight pitch correction for sound, though).

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



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