# How Long is the interval between each frame of a movie?

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### #1 meurglys0

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Posted 09 June 2006 - 12:48 PM

Hi.

I'm new in this forum. I'm a cinema student. So maybe I should know the answer, but I don't.

I need an urgent answer to this question I need to ask for my thesis project...

You know every film is made up of separate still images projected in rapid succession to create the illusion of motion... I found only 1 source giving information on "the interval between the projection of each frame" and it says it is 6.95 miliseconds. Since it's only one source, I thought I need to ask to be sure...

So if you know, please tell me.

Regards.
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### #2 Jason Debus

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Posted 09 June 2006 - 01:22 PM

I'm under the impression it's 50% on 50% off, at least that's what they taught us at school. So your 'in the dark' half the time your watching the movie, 1/48th of a second dark then 1/48 of a film frame. Not sure if this is accurate though.
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### #3 John Pytlak RIP

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Posted 09 June 2006 - 02:36 PM

Hi.

I'm new in this forum. I'm a cinema student. So maybe I should know the answer, but I don't.

I need an urgent answer to this question I need to ask for my thesis project...

You know every film is made up of separate still images projected in rapid succession to create the illusion of motion... I found only 1 source giving information on "the interval between the projection of each frame" and it says it is 6.95 miliseconds. Since it's only one source, I thought I need to ask to be sure...

So if you know, please tell me.

Regards.

It really depends on the shutter angle being used.

The exposure time is calculated by:

( 1 / frame rate) X (shutter opening degrees / 360) = Exposure time in seconds

The "dark" time is calculated by:

(1 / frame rate) X ((360 - Shutter opening degrees) / 360) = dark time per frame in seconds

Cameras often use a shutter opening of 170 or 180 degrees.

Projectors normally use a two or three blade shutter to increase the "flicker" rate to minimize flicker perception. Most "intermittent" pulldowns in a projector require a shutter blade of about 90-degrees, although some high speed intermittent designs can be used with smaller shutter angles without having "travel ghost".
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### #4 James Steven Beverly

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Posted 09 June 2006 - 08:53 PM

Wouldn't also depend on FPS? At 18 frames oer second which is what silent films are projected at the rate at which the image of each frame was on screen would be longer than at 24fps and digital which scans at 29.97 for NTSC interlaced and 25 for PAL . Of course video set at 24 progressive would be the same

Edited by Capt.Video, 09 June 2006 - 08:56 PM.

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### #5 Luke Prendergast

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Posted 10 June 2006 - 04:35 PM

digital which scans at 29.97 for NTSC interlaced and 25 for PAL . Of course video set at 24 progressive would be the same

But there's no dark between the frames in video.

To the original question - are you wanting to know the time between one image and the next, or the dark time between their projection?
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