Re: syncing 2 16mm projectors

From: Dylan Armajani (email suppressed)
Date: Wed Sep 26 2007 - 10:05:44 PDT

When it comes to dvd players.... Guys... Run 1 unit and split the signal to
2 projectors. Fixes your little issues.


On 9/26/07 12:39 PM, "Jeff Kreines" <email suppressed> wrote:

> On Sep 26, 2007, at 5:09 AM, Joost Rekveld wrote:
>> I did, for two projections during a dance-piece, and two dvd-players of the
>> same brand, same type, will typically give you about 5 to 10%  difference,
>> say about two minutes out of sync after half an hour. I've never met somebody
>> who could explain to me why this happens, but it is reality.
> That's a lot of drift.  Most digital consumer devices will hold sync pretty
> well for 15-20 minutes -- which is why cheap MD recorders can work nicely for
> double system sound with a DV or HDV camcorder.  Drift is maybe a frame every
> 15-20 minutes, easy to deal with.
> It's hard to common-start DVD players perfectly.  But two minutes!  Wow!  I
> guess there's still a place for time code in this modern world.
> As for sync motors and selsyns, the were cool at the time and worked, but
> Magnatech went to stepper motors in the 70s, and MTM went to servos, and both
> were simpler and more elegant and easier to keep in sync, with simpler
> wiring.  You can slave a Magnatech et al to any projector using just a simple
> shaft encoder, which transmits pulses based on the frames, and will follow the
> projector in forward and reverse faithfully.  
> If you are only needing to start once and go forward, synchronous motors
> "common started" (the same switch is ideal) will hold, but you need to test to
> see if one machine lags on start time.  You can do this with loops of punched
> leader, with non-even spacing, so drift is apparent.  Then just start the
> machines threaded up to compensate for the offset.  A pain, but it's how mixes
> were done in the old pre-selsyn days.  (Yes, I go back that far...)
> Jeff "old fart" Kreines
> __________________________________________________________________ For info on
> FrameWorks, contact Pip Chodorov at <email suppressed>.

For info on FrameWorks, contact Pip Chodorov at <email suppressed>.