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This section has text and photographs derived from some of the v2.5 media, so there may be some differences between the version you have and the screen shots or other material. Please read all the instructions is the other parts of this HTML documentation before trying to build this cine film recorder. This description of the cine film recorder, and computer controlled cine film camera, is intended only for use in testing DANCAD3D.EXE (tm).
See also Section: 3.80.0.0 and Section: 9.75.61.0 for information about DANCINEL.EXE (tm) to display 2048x1536x32 high resolution Digital Cinema like image frame files on the monitor in your cine film recorder and have DANCINEL.EXE (tm) automatically operate the cine film camera and filter wheels.
See also the video about building a cine film recorder in Section: 4.0.0.0.
Steps to build a computer controlled cine film camera.
Purchase or find a movie camera with a external shutter drive shaft.
Make a mounting for a gear reduction synchronous motor to the camera's drive shaft.
Fit the motor shaft coupling with a cam that will open and close a micro switch each time the camera shutter is open or closed, i.e. a 180 degree cam if you are using a single frame drive shaft, or a 22.5 degree 8 lobe cam if you use a 8 frame per turn drive shaft.
Build the amplifier and relay to control the motor.
Wire your computer's speaker for a signal tap.
Use the macro signal command to test the motor start and stop, and adjust the cam on the motor shaft to have the shutter stop fully open or closed.
The initial state of the computer controlled motor is stopped with the shutter closed. The first state occurs when there has been no signal long enough for the motor to turn from the stopped and open position, if the signal did not stay off after the previous state the motor would not stop with the shutter closed. Use the macro command DELAY after the macro SIGNAL command to give the motor time to close the shutter before the next open signal starts, that way you always keep the computer running "behind" the camera motor's motion. If a 1 RPM motor is used on a 8 frame per turn shaft, it will take 3.75 seconds for the shutter to open, and another 3.75 seconds for the shutter to close (60/16=3.75). It takes the same amount of time to stop in the open position as it does to stop in the closed position, but the exposure time is influenced by the shutter angle which ranges from about 270 degrees down to 1 or less degrees, with 170 degrees being typical. The signal from the computer's speaker must have a duration longer than the open or close time. The minimum exposure would be the sum of the opening and closing times multiplied by the fraction of the shutter exposure angle. Since a time exposure is normally made the minimum shutter angle must be greater than the frame height, otherwise you would get a shadow of the stopped shutter blade over your exposure aperture. The length of the exposure is then the minimum plus the dwell caused by prolonged signal from the computer. The length of time the macro SIGNAL command lasts is set by the signal duration delay value, see Appendix B.
In the photo the oscilloscope shows when the signal on the computers speaker is present, here about 32000Hz was used. A small flash light (lamp) was placed behind the camera's aperture so that you can see the light in the camera lens when the shutter is open. When the signal on the computer's speaker starts the motor begins to turn, and so the shutter opens. The motor continues to turn until the cam trips the micro switch, which stops the motor until the signal stops, so to make an exposure the tone must stay on until you want the shutter to close again.
When the motor turns so that the shutter is fully open the micro switch stops the motor from turning. The shutter will stay open, and the motor stopped as long as the tone from the computer's speaker continues. The duration of the tone is controlled by the macro SIGNAL command, and is used to adjust the exposure time.
When the signal stops, the motor begins turning again. As the motor turns the shutter in the camera closes, and then the pull down claw will get ready to advance the film one frame.
When the motor has turned enough the micro switch will toggle back to the initial state and the motor will stop turning and the shutter will be fully closed. The camera is ready again for another signal from the computer to start the exposure cycle again. The signal from the computer must be sounding longer than the time it takes the shutter to open and the motor to pause while the signal is on, i.e. if it takes 1.5 seconds for the shutter to open the minimum time the signal should be on should be 2 seconds or longer.
When you make your cam, you need to have a set screw or clamp so that the cam can be rotated on the motor shaft to have the micro switch trip when the shutter just comes fully open, and again when it is fully closed. Since there can be a lot of backlash, you will need to run the motor several frames and find the average set point for the cam that keeps the shutter blade out of the corners of the frame. Most cameras have a 170 to 190 degree shutter so the spacing between the open and closed switch points is generally about equal. Getting the switch points to be equally spaced may require adjusting the shape of the cam, e.g. by using a file to change the height of the cam and in turn the point the cam is at when the micro-switch changes from off to on, or on to off.
The micro switch needs some adjustment to make up for the different points in it's switching on and off. The cam phase (rotation adjustment set screw) can only set the point for one of the switch trips, so the distance of the switch from the cam face needs to adjust for the spacing of the trip points. The rounded corners on the cam allow the trip points to be adjusted, because you can have the switch toggle at different points on the rounded corner by adjusting the distance between the switch and the cam.
When you position the switch you need to do so in such a way that the end of the switch lever does not catch on the cam. The steep rise and fall of the cam I used was to try to have all 8 lobes act the same, if the slope is slow the shutter might stop a different amounts of openness.
Since the camera is going to make a time exposure of about 5 to 20 seconds, you can use a small gear reduction timing motor to turn the shaft. To keep the exposure time constant the motor should be of the synchronous AC type, in the US that would be 120VAC 60Hz. Synchronous motors are made for timing operations, and are similar to electric clock motors. If you do not use a constant speed motor you may get a flicker in the final film. Also be sure that you do not use a multi-tasking OS or anything else that would effect the timing of the computer while it sends signals to the motor. Note the flexible coupling between the motor shaft and the camera shaft coupling. It is important to use a flexible coupling to avoid breaking off the shaft inside the camera, which in the case of the BOLEX (tm) is something that can happen since it has a very narrow shaft that is cross drilled for a pin. Notice that the camera run button in the front is locked in the run position. The BOLEX (tm) also has a lever in the rear that disconnects the camera spring, so that the camera can be run continuously from the external motor drive shaft.
The high gain signal amplifier is located in a shielded box near the camera drive motor. The amplifier boosts the small signal tapped off the computers speaker to a strength that will operate a relay to control the 120VAC timing motor. The blue thing is the relay, the large TO-3 transistor drives the relay coil. The two switches on the front of the circuit box are the on-off switch and the single-off-continuous switch. The single setting moves the motor one frame at a time under the computer's signal control, and the continuous setting runs the motor forward without the computer's signal so you can run in and run out the head and tail leader for threading of the film into and out of the camera. The photo shows the circuit board and other electronic parts, normally a metal cover would be on the metal box to shield the circuits from RFI and EMI. See the schmatic in SECTION: 5.1.2.1 for details of this circuit.
SECTION: 5.1.2.1 Schmatic of the cine film motor for the animation camera.
