Film-Tech Forum ARCHIVE: Projector Loops

This is topic Projector Loops in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Iben Jimenez (Member # 3713) on 04-12-2006, 10:32 AM:

What is the purpose of the loops of film in the projector?

Posted by William T. Parr (Member # 677) on 04-12-2006, 10:35 AM:

The purpose of the loops in the projector is to keep the fillm from slamming tight against parts during the intermitten's pull down/stop cycles.

Posted by Richard Fowler (Member # 893) on 04-12-2006, 11:16 AM:

Woodville Latham in 1895 patented the "Latham loop" to allow slack above and below the intermittent motion in the picture gate. Previous to this film projection equipment ( Edison peephole viewer and camera ) had no "slack" loops which limited the length of presentation and made installing a large light source for projection impossible

Posted by Robert E. Allen (Member # 1351) on 04-12-2006, 01:14 PM:

In other words Iben, if there were no loops the film would rip apart because when the intermittent stops the film in the gate 24 times each second the rest of the projector is still moving.

Posted by Dominic Case (Member # 1830) on 04-12-2006, 07:12 PM:

Apart from feed and take-up, it is essential that film moves perfectly steadily through the analogue optical sound head: just as esssential as its intermittent movement through the gate.

Posted by Monte L Fullmer (Member # 2797) on 04-12-2006, 07:40 PM:

..but, it's fun watching the "rolling loop" mechanism of the horizontal 15/70 IMAX machines - how the loop starts and being created by compressed air in the rotor and rolls along until it disappears at the end when the film exits the rotor...

This method is tons easier on film since there is no tension and stress due to the vertical action of the conventional gate and trap setup.

Here is a story on the "Latham Loop" mentioned in the "Motion Picture Projection", by James R. Cameron (not the director), 1943:

[IMG]http://www.film-tech.com/uploads/uploads05 03/pg-22-x3.jpg[/IMG]

-Monte

[ 04-12-2006, 10:03 PM: Message edited by: Monte L Fullmer ]

Posted by Frank Angel (Member # 248) on 04-18-2006, 05:53 AM:

Even today you can get chills reading this....what an incredible landmark those first exhibitions must have been and what the audiences must have thought seeing moving pictures for the first time. Same with the first Todd-A-O and the first 3D and the first CinemaScope, etc.

You think anyone will get chills or even care when or where the first movie was ever projected using a 1.3K digital DLP projector? [Roll Eyes]

PS -- Monte, Thanks for the post.