Paul_L
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Telecine with an old super8 proiector and raspberry pi

Sun Jul 07, 2013 5:46 am

Hi everybody,

I don't have a Raspi camera yet but I am reading about. My application will be a telecine for digitizing my old super 8 an 8mm movies. My idea is to replace on my old projector lamp with a led , to install a Raspi camera in front of the movie plane and synchronize the projector shutter with the camera by a GPIO pin . The framerate will be between 16 to 2 fps.

For the gurus of Raspi camera :

It is a possibility to synchronize the movie with the projector shutter or I will be obliged to take numerous still pictures and convert after to a movie ?

Can I adapt the optical system of the camera to a macro so I can capture directly the film ?

Thank you

Paul

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DeeJay
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Re: Telecine with an old super8 proiector and raspberry pi

Sun Jul 07, 2013 6:59 am

Have you seen this article? http://www.raspberrypi.org/archives/4214 There are some feedback comments that might be useful.

The details of the project are not online yet, but the link to them is http://mepler.com/Kinograph
How To Ask Questions The Smart Way: http://www.catb.org/~esr/faqs/smart-questions.html
How to Report Bugs Effectively: http://www.chiark.greenend.org.uk/~sgtatham/bugs.html

Paul_L
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Re: Telecine with an old super8 proiector and raspberry pi

Sun Jul 07, 2013 10:37 am

Thank you . I haven't seen the topic you sent me. Is interesting but even I own a good DSLR I don't think that is a good solution due to the limited number of shutter operations. It will be killed for a few hours of movie digitising. That is the reason that I was thinking of using a Raspi camera. For super8 i think that 5MP is more than enough. the issue is the synchronization of the camera with the movie.

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Burngate
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Re: Telecine with an old super8 proiector and raspberry pi

Sun Jul 07, 2013 11:30 am

Wikipedia http://en.wikipedia.org/wiki/Telecine

Synchronization to video is probably a no-no. Even if there develops a way to either synchronise the camera to an external signal, or output a frame-rate signal to external equipment, there's the problem of the camera's rolling shutter. The film will have to be kept still during the active TV frame, then moved rather rapidly to the next frame during TV frame blanking.
That was done in some telecines using mechanics, but could destroy the sprocket holes. Another way was to use a rotating prism to keep the image stationary while the film moved.

Paul_L
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Re: Telecine with an old super8 proiector and raspberry pi

Sun Jul 07, 2013 11:56 am

In my case the mechanics of the projector is doing the film moving. It is true that it is a bit stressing for the film but it will work for a few times. The projector has also a shutter. The image capture should be syncronized with this shutter.

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Burngate
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Re: Telecine with an old super8 proiector and raspberry pi

Sun Jul 07, 2013 3:05 pm

As I understand it, the Pi camera's rolling shutter is exposing a bit of the image at a time, throughout the active TV frame. This means the projector has to be projecting the film throughout that TV frame, so the projector shutter has to be open and the film stationary throughout the active TV frame.
The only time the Pi camera's sensor isn't actively gathering light is during frame blanking. Quite a short time to close the projector shutter and move the film.

If it's a normal (old) 8mm projector, then the shutter will be closed most of the time, so the film has plenty of time to move.
But the Pi camera will only see the image for that short time, and will only give you the part of the image it's looking at while the projector shutter is open.
So you'll get a band across the picture, with black above and below.

But I could be wrong. It won't be the first or last time.

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mad-hatter
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Re: Telecine with an old super8 proiector and raspberry pi

Sun Jul 07, 2013 4:36 pm

Hello,

Most projectors and cine/movie cameras have a revolving shutter, with appox. a 170/175 degree cut out. The film is stationary
while the image is exposed (camera) or projected (projector). Film transportation occurs when the shutter is closed. Its a
mechanism called fast pull down and been working well for over 100 years. Film goes through the projector/camera at 24 fps.
so the exposure or projection time is approx. 1/50th. of a second and the transportation is approx.1/50th. of a second. Synching
the shutter to an external device is quite common. (opto, reed, led, many ways). If 1/50th. second is too fast a time for the Pi
camera, run the projector slower, 1/2 - 1/4 - 1/8 speed, whatever suits. For the UK TV the film is normally transported at 25 fps. to
allow easy synching (so you are seeing a shorter movie).

Regards

Paul_L
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Re: Telecine with an old super8 proiector and raspberry pi

Sun Jul 07, 2013 5:44 pm

It is not a problem to run the projector slower. Mine has an potentiometer powering the motor so I can adjust continuously. The Raspi camera does not have a mechanical shutter. so it is not a problem for wearing as it will be in case of a DSLR . The time for acquiring a frame ( it is possible to acquire 30fps in full hd ) is much shorter than the time when a frame is stable and the shutter open even my projector has double rate shutter. I don't see here a problem. The problem is that the software ( driver ) allows me to use a external signal for synchronizing the frame acquisition. If not in a movie I can still make still image acquisition and assemble them in a movie later . I will order a raspi camera to make tests

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mad-hatter
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Re: Telecine with an old super8 proiector and raspberry pi

Sun Jul 07, 2013 6:29 pm

Hello,

You have got to modify the projector slightly, to get a signal when the shutter begins to open.
(opto, reed, led, many ways)
Regards

Paul_L
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Re: Telecine with an old super8 proiector and raspberry pi

Sun Jul 07, 2013 6:43 pm

This should be no problem , an optocoupler on the revolving shutter will solve this . The main problem that I am not able to evaluate now is the modification of optical system. The projector has a 18 mm focal objective with 1:1.4 apperture. how can I place the image on the sensor is the problem that troubles me now.

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mad-hatter
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Re: Telecine with an old super8 proiector and raspberry pi

Sun Jul 07, 2013 7:54 pm

Hello,

I'll give you some hints.
Look up the technique of aerial image animation.
Look up the technique of aerial image optical printing.
When you've a basic understanding of the principles come back.
This technique involves optical condensers and lenses and can get quite complicated
and expensive compared to the cost of the Pi.
I think you idea of a led light source is a no go, not enough light.

Regards

Paul_L
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Re: Telecine with an old super8 proiector and raspberry pi

Sun Jul 07, 2013 8:09 pm

I was thinking at a 3W led from avago. The idea is not to heat the film al a low fps setting.

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mad-hatter
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Re: Telecine with an old super8 proiector and raspberry pi

Sun Jul 07, 2013 8:52 pm

Hello,

I still don't think a led light source will have the amount of light output you will need.
Consider a fan on the lamp and a glass heat filter.
The other thing to think about is the colour temperature of the light source.

http://www.lightbulbs-direct.com/articl ... emperature
http://www.theprojectorpros.com/learn-s ... rature.htm

I'm not trying to dampen your project, its quite a good use for the camera module,
but it does need a little more thinking about to get acceptable results.

Regards

poing
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Re: Telecine with an old super8 proiector and raspberry pi

Sun Jul 07, 2013 9:39 pm

I'd try to film the normal projection on a sheet of paper. Digitizing photographic slides this way gives quite good results.

Paul_L
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Re: Telecine with an old super8 proiector and raspberry pi

Mon Jul 08, 2013 7:52 am

I intent to use a LED that will have around 100 lm luminous flux , cool white ( 4500-10000K ) . You can see the datashii from the atached link . The projector already has a fan and a heat filter that falls automaticaly when the framerate is low but this filter is made from two glass sheets and a perforated metal sheet and is reducing much the light. For the spectral structure of the light in the first stage I don't see a problem since 95% of may films are B/W

http://www.avagotech.com/docs/AV02-2428EN

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mad-hatter
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Re: Telecine with an old super8 proiector and raspberry pi

Mon Jul 08, 2013 8:37 am

Hello,

I was wrong about the shutter, I'm used to dealing with a different system of professional equipment.
Most projectors and cine/movie cameras have a revolving shutter, with appox. a 170/175 degree cut out.
It would seem the standard revolving shutter has two opposite cutouts of approx. 85 degrees, to improve out of balance
forces and cut down vibration. The shutter runs at half speed. I apologize for my error.
It is quite probable that what you are suggesting will work fine with B/W film. With low light, just run slower.
The only problems left I think, will be to get an even illumination across the frame. You may need a field lens in the light path
to collect enough light. The other problem will be to get the camera to pickup the projected image. One way is an aerial
image system (my previous post mentions this). You could also try a semi-translucent screen between the projector and
the Pi camera. Its going to need a bit of experimenting. I wish you luck.

Regards

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cyrano
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Re: Telecine with an old super8 proiector and raspberry pi

Mon Jul 08, 2013 9:58 am

I'd expect black and white movies to be more of a problem with a led. That's why I would use a 12V 20W halogen bulb. Led's have several peaks in their output spectrum and with a color video camera that would produce a slightly degraded video signal.

The halogen bulb is bright white, powerful and has an even spectrum. You will end up with less pixels that are between black and white.

I've never tried it. Still waiting for a couple of camera's... :lol:

Paul_L
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Re: Telecine with an old super8 proiector and raspberry pi

Mon Jul 08, 2013 10:00 am

Thank you for your suggestions. My projector has three blades in the shutter if I remember well . It is a russian projector from the '80. I think I will use it at 2..5 FPS. My ideea is to have a single optic system to project directly the image on the Raspi camera sensor. I am not sure if this is possible since I will have a reduction from 8 mm diagonal on film to 4 mm diagonal sensor dimension.

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mad-hatter
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Re: Telecine with an old super8 proiector and raspberry pi

Mon Jul 08, 2013 12:31 pm

Hello,

I don't think so. You need to get appox. 2:1 reduction on the projected image. 8mm film to 4mm camera sensor.

Regards

centaur0rpi
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Re: Telecine with an old super8 proiector and raspberry pi

Sun Aug 04, 2013 4:01 pm

I've just come to this subject and what is concerning me is the conversion from 16>25fr/sec. I am thinking that if alternate frames were taken and morphed over three frames that would give 16>24, so only an extra frame each second would be requires. The Rank machine for converting feature films at 24f/s to 25 used a continually moving film so that it could be moved faster, and some scanning mode to transfer to 25fr.sec film; I did see it in detail but I've long forgotten. Electronics should do it fine today.

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mad-hatter
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Re: Telecine with an old super8 proiector and raspberry pi

Sun Aug 04, 2013 5:54 pm

Hello,

The OP doesn't have a scanner and the precision projection equipment required or probably the money that Rank had to
make/build such a system. He has a projector and a Pi.
There are systems (that have been around for donkey's years) for stretching the film time, where selected frames are duplicated.
To correct 18fps. to 24fps. you would double frame as shown. Each x shows a double frame of the one above.
- --- --- --- --- --- -- 18 Fps
xx--xx--xx--xx--xx--xx-- 24 Fps

You could do the same for 16fps. to 24fps. You would never notice the slight speed up.
You will never notice if this has been done (persistence of vision and all that). The double frames will will not be seen, it will
appear as continuous motion as the brain normally only sees what it expects to see. A similar system applies when you want to
speed things up. You would skip frames rather than duplicating.

Regards

konton
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Re: Telecine with an old super8 proiector and raspberry pi

Fri Feb 14, 2014 10:10 pm

I haven't seen any forward movement on this post, but I am doing something similar. My questions is, can I execute the raspistill command 5 times a second? Will that work or must it be executed at much slower speeds?

My plan is similar to time lapse video, only at a much faster rate. I'm using a projector that can run a 5fps, with a trigger that sends a signal each time the pulldown claw places the frame into the gate. I have removed the shutter on the projector for this process. My hope was to take a still of every film frame, and then when the process is over, compile the photos into an 18fps video.

Thanks for any help on this!

Jae

gcraig102
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Re: Telecine with an old super8 proiector and raspberry pi

Fri Mar 21, 2014 10:35 pm

I'm working on telecine with the pi and camera. I have the Eumig mk8 projector fully controlled, advancing one frame at a time giving the camera a chance to capture each frame. If you search the web for diy telecine you can see what kind of mods are needed. I have a geared DC motor fitted. power by a 12V transformer, rectifier and L6203 motor controller chip. The pi gpio connects to this and with pwm can run slow enough for single frame and at full speed for winding or in reverse for rewinding film. I also have pwm to control the led lamp (no you don't use any form of filament lamp). The lens on the camera is not suitable. If you unscrew the lens (difficult), you can focus on the film, but it is too wide angle. You need a longer focal length. The standard one is 2.8mm. There is a much better range of lenses available in s-mount m12 size. I've ordered a new 3.6mm lens and board mount, though my calculations show the focal length may need to be between 4mm and 12mm.

BerryPicker
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Re: Telecine with an old super8 proiector and raspberry pi

Sat Mar 29, 2014 6:23 pm

To avoid flicker or strobing, and to keep motion smooth, the recorded frame rate must be synchronised with the projector shutter. I use a photodiode to sense the projector shutter. My projector shutter has 3 blades, so there should be 3 x18 = 54 or 3 x 16 = 48 shutter pulses per second. Synchronising the projector shutter to a recording rate of 50 fps does slightly change the speed of motion but the effect is not noticeable. If recording at 25 fps first divide shutter pulses by 2 before comparing them with the recording fps. With this technique some of the recorded frames will expose over 2 adjacent film frames, and this might be noticed, but there is no picture judder when viewing recordings on N x 100Hz TVs.

gcraig102
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Re: Telecine with an old super8 proiector and raspberry pi

Wed Apr 02, 2014 12:18 pm

I don't think you can run raspistill at anything like 5 fps, mine is much slower. You can use the Pi to run a projector at one frame at a time. There are plenty of examples on the web of changing the motor for a 12V DC geared one and fitting a sensor to mark each frame. You can change the Pi camera lens for a more suitable one. 8mm focal length seems minimum.

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