Harold is correct - I used to project 35MM films from reels. The reels 
last about 20 minutes before you need to cutover to the other (B) 
projector. There are actually 2 sets of dots - on the first you turn on 
the motor of the B projector, on the second you throw the shutter switch 
which completes the cutover. The you rewind the reel, setup the NEXT 
reel on the A projector, wait 20 minutes and do it again. This has all 
but gone away as most projection is now done using a huge (3ft+ dia) 
horizontal "pancake" with the entire movie cut into a center feeding 
endless loop. Next comes digital projection.

As for the "watermarking" I mentioned, I believe it's actually not the 
classic *Fraunhofer* Institute copy serialization we are used to but a 
different technique meant to confuse the camera and render the recorded 
image unusable - about which I dare not guess.

Alden


Harold Hallikainen wrote:
>> For years I wondered what the brown oval blob that occasionally showed up
>> on
>> cinema screens during the movie was (usually top right corner).  A couple
>> of
>> years ago I discovered it was an anti-piracy thing.  Not sure how it was
>> supposed to work, apparently it upset cameras somehow.  It was also
>> supposed
>> to be invisible to people.  Right.  Annoys me more now that I know what it
>> is.
>>     
>
> I think the top right corner blob is just a signal to the projectionist to
> start the next reel. It is something like 10 seconds before the next reel
> starts. If you watch the movie, there's typically a scene change 10
> seconds (or whatever it is) after the blob. Theatres now splice all the
> reels together for playback, so the blob is pretty meaningless (unless
> some still play the show reel by reel).
>
> Harold
>
>
>   

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