[tig] State of the art for 3-perf?

Peter Swinson peter_swinson
Wed Sep 15 19:03:09 BST 2004


Young Mr  Orton of the Antipodes was asking generally about 3 perf 35mm.

A point that comes to mind where precision is important is steadiness.

I may be repeating myself or someone elses posting here !


Kodak punch their perfs in groups of 4, OK 8 if you are counting both
sides.

They reference the punched set to a perf on the previous punched frame.

Therefore their punches have 5 pins, One locates in previous frames perf
while 
four punch new frame

This guarentees that , subject to the punches not being worn, a group of  4
perfs
will always be positioned exactly the same as  a previuos set or next set
of 4 perfs.

Now consider tha the punch is slightly skewed, the 4 perfs will skew on the
film,
but ths does not matter as the camera pins will always located in the same
perf
in the group of 4.

HOWEVER with a 3 perf camera the pins will enter a differernt set of the
punch 
group of 4 perfs on each pull down, only repeating for a "same 4 perf hole"
after
4 pull downs.

This can mean instability that repeats in cycles every 4 frames !

It depends of copurse on how parallel the punch was to start with

cheers

Peter Swinson

Peter Swinson Associates Limited

BTW Mike, Have you found any pretty sheep down there yet ?





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