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Film Look, Frame Rate & Shutter Speed

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eric dole
Film Look, Frame Rate & Shutter Speed
on Apr 8, 2011 at 8:44:24 pm

I'm still not 100% clear on the relationship between the frame rate and the shutter speed, if I am going for the "film look."

If I am shooting 24p, then I shouldn't use a shutter speed over 1/40th? Correct?

Eric


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Steve Crow
Re: Film Look, Frame Rate & Shutter Speed
on Apr 8, 2011 at 9:25:25 pm

I'm not sure there is a direct relationship:

Frame Rate: the number of frames that make up one second of the video - traditionally set a 24

Shutter Speed: how fast the shutter on the camera physically opens and closes - 1/50th of a second for a 24fps frame rate

Both contribute to the "film look" but in different ways - one is just more tied directly to the camera and the other is more of an editing/software kind of issue.

Perhaps you are thinking of the 180 degree rule that says your shutter speed should be twice that of the frame rate - that ratio best emulates the operating characteristics of traditional movie film cameras. You can deviate from this rule to give you either a more staccato or softer/blended look to the video.


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Phil Balsdon
Re: Film Look, Frame Rate & Shutter Speed
on Apr 8, 2011 at 10:14:57 pm

Film cameras have a shutter like a disc that spins through 360º. Half this shutter is covered and shields the light from getting to the film plane for half of its rotation. The purpose of this is for the film to move on to its next frame for exposure during the dark phase and put the next frame statically in place for its exposure. This effectively gives each frame a 180º exposure, in other words half the frame rate. (On more complex film cameras this can be changed).

Translated in DSLR or video this means you need to use an exposure (shutter speed) of half your frame rate (fps). So at 24p (fps) you ideally need a shutter speed of 1/48sec. This is not normally possible so 1/50th will be best and at 30fps you should use 1/60th. This is a very subtle effect, almost subliminal.

Choosing a shutter speed much faster than frame rate won't necessarily give you smoother video, in fact if you are panning with a moving subject and have a lot of sharp background detail its likely the image will get a strobe like effect if the shutter speed is 1/400th or faster.

Another thing to consider is your frame rate when shooting under fluorescent lighting. If you're in a country that normally transmits television in the NTSC system its likely fluorescent lights will have a cycle rate of approximately 1/60th second, you should look carefully at your image to see if there is any "flicker", its likely 1/60th of a second shutter speed will be preferable to 1/48 even if you are shooting at 24fps. I'm lucky, I live in country were its PAL and everything syncs with 25fps and 1/50th sec. (except CRT computer screens, but lets not go there)

Cinematographer, Steadicam Operator, Final Cut Pro Post Production.
http://philming.com.au
http://www.steadi-onfilms.com.au/


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Clarke Smith
Re: Film Look, Frame Rate & Shutter Speed
on Jan 15, 2012 at 12:29:43 am

a very good reply is posted on Vimeo.com -



Clarke L. Smith
Camera Operator
CBS Evening News with Scott Pelley
New York City, USA


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