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Shutter times during filming in a green screen studio?

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Lennart Holterman
Shutter times during filming in a green screen studio?
on Sep 11, 2017 at 5:40:50 am

Hello there,

I am filming in a green screen studio, i film with 25fps. Now most people advise me to shoot either with a shutter speed of 50 or 100, when you shoot with 25fps.

So this is what i do, but i do not really understand why? My camera also has a 60 and 80 shutter option.

Maybe there is somebody who can explain to me why i shouldn't use the 60 or 80 shutter possibility on my camera?

Or maybe i could use it? Cause it would be very handy if i could use the 60 or 80 shutter.

I film with a:

-Panasonic Lumix G7 with an Atomos Ninja Flame recorder (prores HQ 422 8 bit)

-Samyang 12mm fix lens MFT

-I mostly use F-stop 2.4 or F-stop 2.8 (with both settings the whole Frame, where my subject is standing is in focus, from top to bottom and from left to right)

I hope somebody can explain me a bit more about the shutter times ☺

Thanx in front

greetz Lenny


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Todd Terry
Re: Shutter times during filming in a green screen studio?
on Sep 11, 2017 at 3:57:23 pm

People are always confusing shutter speed with frame rate (which is an easy mistake to make), but you seem to have a handle on that fortunately...

There has been tons of discussion here about shutter speeds in the past... if you do a search you'll probably find lots of useful threads, but I'll try to quickly explain it.

Traditionally, a "normal" shutter speed is considered "One over twice the frame rate." That is, if you are shooting 24fps, a "normal" shutter speed is 1/48th of a second. Shooting at 25fps, as you are, would be almost the same... 1/50th of a second.

Ok, so what is "normal," and why is it "normal"? Well, going by that equation (1/2xFPS), that emulates the same shutter speed as a film camera shooting with a 180° shutter. If you have a still or slow-moving subject, images are pretty darn crisp. If you have a fast-moving subject, then individual frames have motion blur in them... the more (and faster) the motion, the more the blur. Some people might think "Why don't I just shoot with a faster shutter speed, so images are really sharp and crisp? Isn't that better?" Well, no. The thing is, your brain needs that motion blur in order to perceive the action as smooth. Crank up the speed and you get the "narrow shutter look," where the action looks very staccato and choppy. Sometimes that is desirable and done for effect. See "Saving Private Ryan" for that effect used very well. See almost every action movie out today to see that effect overdone. It has become a staple effect these days for action sequences, car chases, and fight scenes. And yes it does make action scenes look more "action-y." But for everyday shooting and common action, that's usually not the effect you'll be wanting.

So... yes, you can shoot with higher shutter speeds, as you suggested. But the higher you go, and the farther away from something in the "normal" range, the more your action will get that "narrow shutter look," and become choppy.

There is one advantage to higher-than-normal shutter speeds with greenscreen work... it can make compositing cleaner when there is lots of movement, because your keyer will be dealing with sharper images and cleaner edges (since there is less motion blur) that make eliminating green fringing around the edges easier. So sometimes, that can be beneficial, but you'll likely want to add some motion blur back in post after your compositing in order to help make the motion look smooth.

That's a rudimentary explanation, but hope it helps.....

T2

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



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Lennart Holterman
Re: Shutter times during filming in a green screen studio?
on Sep 12, 2017 at 7:41:15 am

He Tod,

Thanx for your great reply and explanation ☺

I filmed my character with a shutter speed of 100. I have rendered out an example and i am
curious if you think it is to staccato and choppy when he moves? i don't have enough experience to judge on this.

here is the google drive link:

https://drive.google.com/open?id=0B8MudY1Ib6d9NENNRERGeFRqanc

I hope you can find some time to have a quick look at it?

Thanx in front
greetz lenny


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