I am building a telecine machine from a standard 8 projector.
I have a small analogue video camera with a macro lens taking images directly from the film.
I have the vertical sync output from the camera, and I need to syncronize the motor speed to the to the camera. . I have a sensor on the shutter providing a pulse so if the motor can be controlled and locked then transfering would be much easier. if anyone can help please.
Ps the motor is a free running motor. and eddy current brake can be used or a dc motor can be fitted. thanks Pete m
I think you get to the problem from the wrong side. Adjusting a mechanical machine to an electronic signal is by factors harder than adjusting the electronics to a signal the mechanical part provides.
So let the motor drive the film and generate a signal when the shutter opens the image. Let that trigger the camera to save the current image.
The camera is a video camera PAl. system which has a 50hz field rate, the film shutter shows 1 frame with a 3 blade shutter giving 48 frames per second and can be adjusted to 50 frames per second.
A video recorder works on the same principle. by syncronizing the head position with the 50 hz field rate of the incoming signal or the control pulse off the tape, and a sensor on the head drum sends pulses back to the servo. so the head position is at the correct point at the start of each frame.
this must be able to be done with an arduino these days. I have looked into the Philips n1500 control servo, If the head moves to fast the eddy current brake is applied, the motor always would run slightly faster for this to happen, the two pulses are then locked together.
There are a lot of transistors involved in the circuit so it must be possible to achieve the same with an arduino. kr Pete
I’ve done this in a production studio settin - both directions…
The go to path is to control the film speed incrementally, either in the film projector or film camera.
The next step is to not use a standard raster scan style of camera - the reason broadcast film scanners aren’t cheap. The ‘flying spot’, scanners are synchronised to the video frame & line rate - there’s no shutter involved.
I doubt this is possible/practical unless you can synchronize both sides. An old-time projector probably has a synchronous motor, which is locked-into the power line frequency. But, I don't know how you'd lock-in the video-camera side. Power line frequency is very precise and very stable.
If the camera has an analog-PAL output (for monitoring) you can build a circuit to detect the sync-pulse, but offhand I don't know how to do that. I guess that would be the vertical sync-pulse, but It's been a long time since I studied that stuff.
Then you'd have to make something like a phase-locked loop to somehow control the projector speed.
...Probably nothing requiring an Arduino or software, unless you wanted to use that for motor-speed control.
An analog camera is clearly the wrong device for this application. In any case, the question is - for what purpose would you want a PAL output? Generally, you might be using the telecine to convert film to DVD in which case you would use a digital camera and need to arrange it to synchronise to the shutter.
I have used this system and the results have been very good, I tried slowing the system down and taking individual frames directly from the film, and assembling them with software, this also worked well but it took an hour for one minute of film. when there is a lot of 4 minute reels ,this can get very long and tedious work.
So to be able to do this in real time is the better option I just have to keep an eye on the speed of the transport system. and adjust manually. the motor is not locked to the mains and the frame pulses are retrieved from the video out. however if making the motor syncronus, and locked to the mains then drive the motor with the frame pulse this could work thanks kindesr regards, Pete m
This is an interesting concept, thanks to all who have replied so far, your input is very much appreciated. There are some ideas that I might try out, the sync shutter may be possible with a rotating magnet and a coil generating a field derived from the frame pulses.
Garrard turntables used a similar idea on there motors back in the 70s. the motor was designed to run slightly fast, and the magnet would lock the rotor to the mains frequency. keeping the turntable at the correct speed. KR pete M
There is another approach not mentioned yet…
A line scan CCD (or similar), with very precise control,of the film movement.
Scan each frame to a buffer - line by line, and save them sequentially to your preferred in-compressed video format.
With a fast enough cpu and storage, you can scan at multiples of the ‘normal’ frame rate, but costs will climb due to the increased mechanical precision and processing power.
Using an Arduino UNO it can be done using a standard (8mm film) projector and a video camera. First step is to remove the projector motor and transformer and replace it with a DC motor (one removed from an old ink jet printer, usually runs on 31volts). This motor will now be driven by the Arduino thru a power MOSFET (BUK457, IRFZ44n, etc, or a L298N bridge if you prefer). Next, cut off two blades of the three bladed shutter and mount a LED-Photo diode detector (also obtainable from an old ink jet printer), so as to supply an interrupt to an Arduino Interrupt pin so as to mark the point where the Projector shaft is.
Next, using a Digital Video Camera (I use a Canon EOS 550D) take the A/V output and connect it to a Video serration IC. I use a LM1881. An output of this IC is a FRAME pulse to which I connect to the second Arduino Interrupt pin. This A/V output will need to be split to supply a Video to a TV set so as to view what the Camera is seeing.
Now comes the interesting part, writing the software to make the projector run in lock-step with the Video Camera and thus make a one-to-one grab of the movie film images at 25frames per second. I can supply this later if there is still interest, or if you are a glutton for punishment you could write it.
I will skip over the Projector/Camera Optics at this point and assume that there is a video file of the movie film on the Camera SD chip. I can come back to this later as the Optical Engineering part is a subject in its own right.
The final part is in Post Production using a Video Editor.
This part will do several steps:-
- Convert the video to High Definition (the Canon EOS 550D records in Full High Definition which is over kill for 8mm film resolution and are a far larger file size than needed.
- Depending on how the Projector/Camera optics are set up, the image can be inverted, hence re-invert the video so that subjects are the right way up and writing can be read from left to right.
- Change the frame rate. The video is at 25fps while Standard 8mm film is usually run at 16fps, and Super 8mm film at 18fps of 24fps.
- Crop the edges to remove the image of the sprocket holes and the other edge to balance.
There you have it. It is a good project to make use of several branches of Engineering, and you do need to have reasonable skill in mechanics, circuit board, software, optics, and digital video processing. And once you have built your prototype you will find ways of improving and/or redesigning it. A guide is not to re-invent too many parts but to use existing equipment where possible. If this looks like a possible way you may like to progress I can post more addressing each specific part of the Telecine Chain.
Thank you Robert this is just what I am looking for. the motor and transformer has been replaced by a dc motor and the camera is fitted inside the projector and the macro lens is focused on the gate, with the light source where the lens would be fitted, the gate has been enlarged so any dust or debris is not left in frame. there is an opto interupt fitted that gives a pulse for every revolution apart from removing the two blades it is almost there. I would be very much appreciated if you can assist with the software, I am new to arduinos and although I have dabbled in using them, most of the files I have experimented with have been from the library. thanks kindest regards Pete M
Pete, you appear to have done the ground work on the Projector chassis, thus there are some of my directions you can ignore. You have an Opto-interrupt already fitted so that you do not need to use a single shutter blade for this purpose, in fact remove the shutter blades entirely as the Camera will need to stare at an un-interrupted film image.
Things you will need are:- KiCAD for schematic capture, Arduino IDE for UNO R3 firmware, and kdenlive for video editing. At least these are what I use.
Now I am a little stumped at how to move forward with you as I need to transfer schematic and firmware listing to you and I think that this will be too complex to put on the forum. I am not aware of others interested in building a telecine chain so in the meantime I think using email will be the easiest, at least until I get around to building a Web page! Thus, contact me at robert.denize@gmail.com.
By the way, I am happy that any of my designs can be freely used, basically Open Commons or Copyleft concepts.
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