Film-Tech Forum ARCHIVE: 42 FPS checking graff card

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Posted by Kevin Baglow (Member # 721) on 10-11-2002, 06:08 AM:

I herd a long time ago there was a pattened card u could attach to the side of a sprocket. Whne the speed was correct the patten gave the ilusion of being still. Any one have one of these or know how acurate they are?

Posted by Frank Angel (Member # 248) on 10-11-2002, 08:47 AM:

I've never seen them used for theatre projectors, but they were very widely used on LP turntables. They required being lit by a neon light light source which strobed the lines. It's a workable idea, but unless you have a special venue projector equipped with variable speed control, there's not much you are going to be able to do about a projector that you discover is running slightly off-speed. Actually it's a bad idea because that knowledge will only make you crazy.

Frank

Posted by Gordon McLeod (Member # 33) on 10-11-2002, 11:28 AM:

Just get an RPM meter or strobe light style

Posted by Frank Angel (Member # 248) on 10-11-2002, 12:58 PM:

Yup.

When I was a kid, I bought this r-t-r recording tape made specifically for syncing a tape machine to a silent projector. I think it was made by Revere. Its purpose was to help would-be filmmakers add sound to a silent film by reason of that the strobe principle. It required you to place the tape machine close enough to the projector so that the light from the shutter would fall on the tape. The base side of the tape had black and white lines on it so that by adjusting the projector speed, you could get the lines on the moving tape to seem like they were standing still. At this point the projector was in sync with the tape. If you recorded a soundtrack while keeping the lines from moving, you could then play it back in sync. Of course you needed someone to sit there constantly adjusting the speed control on the projector so that the lines wouldn't drift, but it did work, and you could get sync sound, of a fashion.

Frank

Posted by Steve Kraus (Member # 476) on 10-11-2002, 08:10 PM:

Now that you mention it, during the Super 8 home movie era but before cameras recording directly on film mag stripe were introduced didn't B&H have system recording sound on audio cassettes? How were those kept in sync...or were they?

Posted by Frank Angel (Member # 248) on 10-12-2002, 01:23 PM:

I recall that; I saw one in the A/V room at college, but never saw it in operation. My recollection is that it didn't give lipsync, only a convenient way of starting and stopping everything together so you could add music as a wild track.

However, there was quite an elaborate system from a company called Inner Space. You sent them your S8mm camera and portable stereo tape deck like Uher or any other r-t-r that used a 12vdc motor. They they modified and retured them to you along with all the components needed to make lipsync soundtracks. The camera modification was so it would give a pulse-per-frame output which was recorded on one channel of the tape.

On playback, an infrared chip that contained an IR led and an IR sensor was glued to the projector so it could read each revolution of the inching knob. The IS resolver would then control the speed of the modified tape deck (the deck modification allowed the DC motor to be driven directly by the voltage supplied the resolver). Based on the comparison of the pulses from the control track on the tape and the pulses from the projector, the resolver would supply the correct voltage to keep deck and projector in sync. This system could resolve well enough for lip-sync. I experimented with it and tried to copy a short segment of a 35mm film to S8mm. It worked flawlessly. It was very useful in film schools because for very little $$, they could build a complete system with editing and mixing that taught all the principles film without the high cost of even using 16mm.

Then along came video.

Frank