Syncing cine to camcorder. How to control speed?

[tmd1]

Hi There,
I tried the search but couldn't find anything. In order to transfer some old cine to video, I need to find either a better projector which can sync the speed to either 16.66 or 25 frames per second, or find a way to control the speed of the projector I have. It is an Eumig P8 and I think it is fairly primitive. It uses a potentiometer to control speed and has no indication as to the speed it is going.
I am not interested in spending a huge amount of money on any solution. Probably no more than €100.
Any help, advice or ideas would be greatly appreciated.
Regards, iwb.

[Aud_Mot]

tmd1,

I would suggest that you do the experiment. Point the camcorder at the movie screen and play with the projector's speed knob. Couldn't hurt, worst will happen is you will have to re-wind the tape and try again. I know some people sneak video cameras into movies theaters and produce bootleg video tapes that way. I have never heard of any special modifications to the camcorder required.

If you are looking for a more professional result:

Ireleand is a PAL type TV standard country. As far as I know, all flavors of PAL are 25 Frames Per Second (FPS), and so your camcorder should also run at 25 FPS. You do not state what type of film you wish to convert, 35mm, 16mm, 8mm, etc. Assuming your film is running at 24 FPS, you have 2 tasks you must accomplish.

One:
Speed up your projector to 25 FPS. You say the projector has a speed knob on it. You can test to see if your projector will go up to 25 FPS (only 4.17%) by running a film, point the camcorder at the screen and turn up the speed until the image is stable. I would suggest that you view the "synchronize-abilty" on a TV that is plugged into the camcorder, do not rely on just the camcorder's viewfinder. You might have to stop and re-start the projector a couples of time to "adjust" problem #2.

Two: Synchronization. You must synchronize the 2 devices so that each one starts their frames at the same instant. The most likely solution is to take the video out of your camcorder (part of the video signal is a sync pulse) and use that as a source of generating a signal to sync up the projector. What kind of signal will your projector accept? Square wave, sine wave, some other format? What peak to peak voltage is needed? Would a timing offest/delay be required? Where would you insert the sync siganl? What kind of modification is needed? How are you going to convert video to the required sync signal?

It is a can of worms for you to do on the your own. If you can find a kit that applies to your specific model of projector, you might try that. I have neverheard of such a thing.

One more solution I see is to use a device called a telecine, a contraction of TELEvision and CINEscope. These are machines that are film in, video out. Look for service that will do the conversion for a fee. Here in America, they are quite common. I would also to have the service (if available) do a film/video to MPEG file and/or DVD conversion while they are at it.

Please post your findings and results.

Regards,

Aud_Mot

[tmd1]

Aud_Mot,
Thanks for your reply and advice. It is 8mm film. All I really want to achieve is to get the projector to run at 25 FPS. The potentiometer is very inaccurate and that is all there is for control on the projector. What I thought was at the least I could get a different form of control for the motor that is more accurate and if possible, a way to monitor the frames per second. I guess this might be a tall order based on the projector itself.

[Aud_Mot]

tmd1,

Did you try the pointing the camera at the screen? What was the result? Maybe with the US TV standard being 30 FSP and the film being 24 FPS is far enough part that you do not get the roll or flashing problem.

One thing that comes to mind: There are some very inexpensive light detector component/devices out there. They should cost less than $1.00 USD. Just about anything you can get your hands on should work. (Some are solar cell-like devices that generate electricty directly, some are resistors that value's change with different levels of light) The only restriction is that it has to be faster than 25Hz. You can experiment, put one of these devices infront of your projector and measure it's output. If you have an O'scope, you are set. If not a Digital voltmeter would work. You might have to supply it with some sort of DC source, like a 9V battery. Depending what your devices does, what you can get out of it and what test equipment you have access to, you might need to buffer/amplify the signal coming off your "light to electricity" converter.

The next thing that comes to mind: I beleive the mains AC power is Ireland is 50 Hz. Twice the frequency you are looking for. If you have an O'scope, you could put your light source signal into the X input and put a low voltage version of the mains signal into the Y input and "beat" the 2 signals against each other. (Please make sure you use a step down transformer for your lines AC source. It will give you a safe, low voltage and also isolate the signal) This will produce a "lissajous pattern" As the frequencies get farther apart, the more the pattern will spin around. As I recall, if one of the frequencies is 2 times the other, you get a nice little bent pattern, but you can easily tell when you have matched the 2 frequencies.

If you remove the speed pot you can measure it's value, estimate how much power it will need to disapate and build a precision verison of the pot. If you can get the pot to "about 25Hz position" and then measure the values of ressitors that create the voltage divider needed. (wiper to "top" of pot and wiper to "bottom" of pot.) Depending on what value you need and what you can get your hands on will determine how to make your new pot. I would start with 2 resistors in series. One of the open ends being the "top" of the pot, the other open end being the "bottom" of the pot and the junction is the wiper of the pot. Then select a large value of (multi-turn if you can get one) pot to put in parrallel with one of the 2 resistors. The parallel pot is used to trim the value of the resistor it is in parallel with.

Good Luck,

Aud_Mot

[Circlotron]

Frame rate is not the only problem - you also have to control the phase of the shutter as well as the frequency otherwise your video camera might be taking pictures of only blanked screens in between frames!

Don't know a lot about movie projectors but I could visualise a photosensor of some sort just past the shutter disc and it would give a sync pulse every time the light fell on it. This and the vertical sync pulse from the camera are both fed to a phase locked loop cct. The PLL output voltage is sent to a mains voltage controller to vary the projector motor speed. By adjusting the angular position of the photosensor you would get the correct machine to machine phasing.