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High speed PROJECTORS


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#1 Refah Seyed Mahmoud

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Posted 11 November 2014 - 11:44 AM

I need a system capable of projecting an image at 120fps+. I understand that certain 3D cinema projectors can reach these speeds if you combine the left and right eyes at 60fps each, but afaik these are all oversize units designed to be hard-mounted into a theater.

 

Would I be able to modify a film projector to run at such a speed? 


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#2 Phil Rhodes

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Posted 11 November 2014 - 02:15 PM

I doubt it. The fastest film projection system of which I'm aware was Showscan, which had to use elaborate measures to achieve 60fps with a 70mm print.

 

P


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#3 Refah Seyed Mahmoud

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Posted 14 November 2014 - 05:32 PM

From what I understand the main issue is the intermittent mechanism - stopping the film in the gate long enough to project it. For my application I'm fine with a continuous pull through the gate. If I wanted to modify a 16 or 35mm projector, how could I get started? I'd need to project only about 30 seconds worth of footage at a time, albeit at 240+ fps.


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#4 Simon Wyss

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Posted 15 November 2014 - 06:45 AM

Which format are we talking? 35? 16?

 

Some flatbed editors allow to remove the screen holder (Steenbeck) and project in the dark. Later Steenbeck models can reach 200 f. p. s. (http://www.steenbeck...mm_01_serie.pdf)

 

Studio synchronizing projectors are an option although probably rather difficult to dig up.


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#5 Mark Dunn

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Posted 15 November 2014 - 08:50 AM

From what I understand the main issue is the intermittent mechanism - stopping the film in the gate long enough to project it. For my application I'm fine with a continuous pull through the gate. If I wanted to modify a 16 or 35mm projector, how could I get started? I'd need to project only about 30 seconds worth of footage at a time, albeit at 240+ fps.

In a projector the film must be stationary when projected. If the film were moving continuously you wouldn't get an image.

The alternative, as Simon suggests, is a Steenbeck with the screen housing off. It uses a rotating prism to compensate for image movement.

The specs claim you can project to about a 32" screen diagonal, but in practice it isn't very bright.


Edited by Mark Dunn, 15 November 2014 - 08:54 AM.

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#6 Dennis Couzin

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Posted 15 November 2014 - 01:58 PM

I need a system capable of projecting an image at 120fps+. .. Would I be able to modify a film projector to run at such a speed? 

 

From what I understand the main issue is the intermittent mechanism - stopping the film in the gate long enough to project it. For my application I'm fine with a continuous pull through the gate. If I wanted to modify a 16 or 35mm projector, how could I get started?

 

@Refah: Do you mean this?  Must someone look at the projection and make out fast action, or do you merely wish to get all the information in 120 frames of film onto the screen in 1 second in such a way that at every instant no more than two frames appear?  Perhaps describe your application.

 

@others: Another kind of high speed projector moves the film continuously and uses a strobe lamp, very accurately synched to the movement.  For 120 fps, a 10 microsecond flash introduces a blur of just 1/833 of the frame height, probably better image quality than a rotating prism system.


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#7 Refah Seyed Mahmoud

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Posted 16 November 2014 - 11:39 PM

So I've dreamed up an effect that I've never seen before and which works in theory, but, of course, the devil is in the details...

 

Imagine a music video:

1. Film the artist performing in regular time, let's say 24fps.

2. Project that 24fps performance at 240 fps onto something moving quickly... dancers, blowing smoke, shattering ice, flowing fabric, etc.

3. Film the interaction of the projection with the objects using a high-speed camera at a matching frame rate of 240fps..

4. Play back the finished shot at 24fps to produce a mix of realtime footage projected onto slow-motion objects.

 

If you let your imagination run freely for a bit, you can come up with all kinds of interesting "time blended" shots, where cigarette smoke blowing from a model's mouth reveals the singer's face, or where the guitar solo is stretched and wrapped across the slowly turning body of a dancer. 

 

The reason I think I can get away without the intermittent mechanism in the projection is that the only shutter that really matters is the one in the high speed camera. Even if the film is moving continuously through the gate at 240fps, a fast enough shutter speed and frame rate in the highspeed camera would eliminate motion blur in the projected image just as it does any other moving object. Synchronizing the camera and the projector would be difficult (maybe even impossible?) but since this would be a very expressive technique anyways, it would be fine to see a bit of the gaps between frames, or even a "film roll" effect as the camera and projector go in and out of phase. A certain amount of trial and error would be in order. 

 

Using a strobe in the projector would certainly do much to remove any remaining blur...


Edited by Refah Seyed Mahmoud, 16 November 2014 - 11:43 PM.

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#8 Dennis Couzin

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Posted 17 November 2014 - 12:00 AM

Expecting the 240 fps camera shutter to freeze the 240 fps non-intermittant projection fails for two reasons.  1. In my example, you need a strobe flash of about 10 microseconds to sufficiently freeze a 120 fps flow, so 5 microseconds for your 240 fps flow.  That's a 0.43 degree shutter.  You'd have to fabricate such a camera shutter and then ... 2. The exposure will be insufficient under any practical continuous lighting with the 0.43 degree shutter.

 

Strobe makes the special shutter unnecessary and provides the necessary exposure.


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#9 Dennis Couzin

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Posted 17 November 2014 - 12:18 AM

Oops!  My analysis of the shutter requirement was wrong.  The 0.43 degree slit would be travelling in an ordinary camera shutter so it would move at only about twice the speed of the flowing image: hence big blur.  If you could set up the camera so its shutter travelled horizontally while the projection flowed vertically, or vice versa, then you could get sharp, but badly sheared, images from the slit shutter. 

 

Go strobe.


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#10 Dennis Couzin

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Posted 17 November 2014 - 12:49 AM

Oops again, although this won't change much.  The slit might be travelling about four times -- it depends on the shutter's cut-off angle -- the speed of the flowing image.  Still big blur. 


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#11 Dennis Couzin

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Posted 17 November 2014 - 08:19 AM

To recapitulate:  One way to film the 240 fps projection at 240 fps is with a 240 fps intermittant motion projector and a 240 intermittant camera.  They are just barely mechanically possible.  Not just the mechanism but the film perfs must withstand the accelerations.  Wheeler estimates the maximum fps for the film at 300 fps.  He wrote pre-polyester based film, but while the poly might not tear it might deform.  If you can find a 240 fps intermittant camera you can probably buy a second one to convert to a projector.

 

The second way is with a 240 fps projector that uses continuous film motion with optical intermittancy.  This is the rotating prism projector, e.g. the Steenbeck movement suggested by Simon Wyss.  The image quality is poor.  You must also find a 240 fps camera.

 

The third way is with a 240 fps projector that uses continuous film motion so the image streams up the screen, but a strobe light to freeze it in midframe every frame.  Building a good projector of that kind isn't easy.  If you start with a basic sproket-loop-claw-loop-sprocket projector, and remove the claw mechanism while installing a roller to keep the bottom loop it can run very fast.  But the streaming isn't well governed.  Those drive sprockets aren't cut precisely and also gate pressure will introduce perturbations.  You're better off using the continuous film transport system from a film scanner of that type.  Some are even stroboscopic but you'd need a much stronger strobe


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#12 David Mullen ASC

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Posted 17 November 2014 - 11:29 AM

I think he should find a digital projector with the fastest refresh rate and make that the frame rate.


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#13 Dennis Couzin

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Posted 17 November 2014 - 02:47 PM

David Mullen's suggestion is the practical way to go.  It's funny that the topic starter and the first three responders thought only in terms of film. 

 

For extremely high speed recording, video cameras can now surpass the Fastax's 10,000 fps. However, the Fastax technique of a rotating prism is equally applicable for camera and projector.  With video, recording and projection are two completely different technologies, and there are not ultrafast video projectors, so far as I know.  Even the sought 240 fps might be impossible today.  Extremely fast video projection should be possible with a DLP chip by sacrificing tonality and color: one-bit video.  That is probably not the effect Refah wants.


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#14 Igor Trajkovski

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Posted 19 November 2014 - 07:06 AM

What about shooting your 240fps footage of dancers, blowing smoke, shattering ice, flowing fabric, etc.
with 2 sync'd cameras, one as the main, the other as reference at some offset angle and distance from main,

and then using the footage from both cameras to extrapolate 3d geometry, depth maps to use

for projecting your artist  24 fps footage in post?

 

The projection would be 1 on 1 frame, with the benefits of adjusting intensity, color, falloff, etc. of the projected footage at your discretion.

 

 

 

Best

 

Igor


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#15 cole t parzenn

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Posted 19 November 2014 - 04:49 PM

Could you use a high speed camera as a projector?


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#16 Simon Wyss

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Posted 20 November 2014 - 04:40 AM

It's funny that the topic starter and the first three responders thought only in terms of film.

 

Why? We’re film people. Video is dreary.


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#17 Dennis Couzin

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Posted 20 November 2014 - 07:09 AM

I miscounted. "first three responders" should be "first four responders".  I meant to include myself, since I also responded in terms of film and I do find that funny.

 

The topic was how to project 120+ images per second.  How to get the light out there, to shine images onto "dancers, blowing smoke, shattering ice, flowing fabric, etc." as Refah later revealed.  It's an engineering question far from the nature of photographic imagery versus video imagery.  Video projectors can shine images onto things, so we should have thought of using them.  David was the first to.

 

Full disclosure: I devoted 16 years to film, then despaired over its future and left image making altogether for 13 years, then took up video (9 years ago).  I thought I'd made the transition from film to video, but I answered in this strand in terms of film because sprockets and genevas are so cute.  You never can forget them.  But cute does not imply profound and cute can even become dreary.  We need to honestly ask what was irreplaceably special about film.  My hunch is that it was not so much the film and equipment as the technological culture surrounding it. Film developed in a whirl of invention and science.  Video is developing in the grip of engineers.


Edited by Dennis Couzin, 20 November 2014 - 07:11 AM.

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#18 Bill DiPietra

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Posted 25 April 2015 - 06:13 PM

 

Free raw footage for editing (action) download http://adf.ly/1FiGq6

 

 

Stop spamming the forum.  That's four of the same post in about 5 minutes.


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