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» Film-Tech Forum ARCHIVE   » Operations   » Large Format Forum   » IMAX platter/threading question (Page 2)

 
This topic comprises 2 pages: 1  2   
Author Topic: IMAX platter/threading question
Brian Michael Weidemann
Expert cat molester

Posts: 944
From: Costa Mesa, CA United States
Registered: Feb 2004

- posted 03-28-2008 03:48 AM      Profile for Brian Michael Weidemann   Author's Homepage   Email Brian Michael Weidemann   Send New Private Message       Edit/Delete Post 
I agree. That's a lot of unnecessarily complicated mechanical design to counteract such a rare possibility.

If the film wraps, the feed unit knows about it before long, and then the console shuts down the projector with a Reel Unit Not Ready fault.

And film doesn't just "break". Any decent enough staff knows to fix worn or bad splices. I've seen mid-show tail-outs only two or three times in the last ten years. I only remember the cause of one of them, and it was operator error. (The guy who moved the film onto the platters, for the show that was playing when I came in, had nicked the top of the print, about half-an-inch, on the outer edge ... just enough to rip the full width of the film as it went through, and it crashed, 30 seconds of end credits left to go. It took a lot of splices to repair the subsequent nicks, located about every 15 feet of the remaining film, to get it to playable status.) We were back on screen, only lost one show, as the tail-out didn't misalign the cam ... just tore up 5 feet of film.

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Tim Reed
Better Projection Pays

Posts: 5246
From: Northampton, PA
Registered: Sep 1999

- posted 03-31-2008 05:00 PM      Profile for Tim Reed   Author's Homepage     Send New Private Message       Edit/Delete Post 
quote: Tristan Lane
It would require a lot of extra work to make the cam pins and the registration pins to retract.
You mean, more work than engineering multiple lamphouses and associated optics, moving 70mm film horizontally at blinding speeds, using compressed air for mechanical control, effecting double-system sound, and dual-strip projectors -- all under computer control and monitoring?

Something as simple as a gate that falls back or pins that retract as a safety measure shouldn't be a major hurdle. How much work did it take to do IMAX Magic Carpet? Or Omnimax? For what, one or two installations?

And, they get how many millions of dollars for these?

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Tristan Lane
Master Film Handler

Posts: 444
From: Nampa, Idaho
Registered: Feb 2002

- posted 04-03-2008 07:42 PM      Profile for Tristan Lane   Email Tristan Lane   Send New Private Message       Edit/Delete Post 
Regardless of the complexity of the modifications required to do what Tim wants, one simple fact remains: There's no reason to do it. Someone should be there to make sure the film stops...regardless of automation.

Projecting IMAX is a job that requires an attentive operator that is present at all times. I believe it is the last mainstream film format that still requires competent operators in every booth. The equipment is expensive, the film is expensive, and minor mistakes cost thousands. Tail out is always avoidable if someone is there to make sure the projector stops.

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Scott Norwood
Film God

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From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99

- posted 04-09-2008 09:25 AM      Profile for Scott Norwood   Author's Homepage   Email Scott Norwood   Send New Private Message       Edit/Delete Post 
quote: Tristan Lane
I believe it is the last mainstream film format that still requires competent operators in every booth.
So there is nothing wrong with incompetent operators (or no operators at all) for 16mm, 35mm, and 70mm?

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Tristan Lane
Master Film Handler

Posts: 444
From: Nampa, Idaho
Registered: Feb 2002

- posted 04-10-2008 01:59 AM      Profile for Tristan Lane   Email Tristan Lane   Send New Private Message       Edit/Delete Post 
quote: Scott Norwood
So there is nothing wrong with incompetent operators (or no operators at all) for 16mm, 35mm, and 70mm?
[Roll Eyes]

It appears so.

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Charles Greenlee
Jedi Master Film Handler

Posts: 801
From: Savannah, Ga, U.S.
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- posted 04-28-2008 12:20 AM      Profile for Charles Greenlee   Author's Homepage   Email Charles Greenlee   Send New Private Message       Edit/Delete Post 
Sadly, yes. Or even no operators, as continual loop platters and automations that automatically start on times would prove. If your projectors start by themselves and don't need to be rethreaded every show, then you wouldn't need a projectionist. [bs] Just another way to replace a competent person who cares for the quality of their job with some minimum wager, or even a computer.

As far as the winding of the leader as such. I can't help but notice the platter rings don't have the button and split. I'm guessing they require the friction of the leader itself to hold it onto the ring? I can imagine having to bring that much leader around to the rewind platter would cause it to end up all over the floor. It looks like it takes a good amount of leader to wrap the ring enough to lock onto it. Actually sounds like a good concept even for 35mm, that way you're not losing leader to that little fold, to slip into the split in the ring, that always wears out. That and keeping it off the floor would make your leader last longer. I like that.

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Mark Gulbrandsen
Resident Trollmaster

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From: Music City
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- posted 05-03-2008 04:54 AM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
quote: Tristan Lane
Also, If the registration pins were moveable, the mechanism would eventually get sloppy and result in an unsteady picture.

Indeed... the reg pins can't retract they are on both sides of the field flattner which can only move up and down. The fact that they are stationary is part of what makes the system so good. On the Iwerks 15/70 clones the only part that goes bad every few thousand operating hours is the cam unit bearings... Nothing else ever really fails in the projector itself unless... One Iwerks system near me that we are involved with originally had no UPS system at all and a power bump would cause all sorts of problems and damage. Talk about inertia keeping things moving! One severe power bump caused the loss of about 300 feet of L eye and R eye picture much of which was wrapped around the lower inside of the mechanisms and all caught up in the drive belts and stuff... it had to all be cut apart to get it out. You don't just grab these platter systems to stop them... you could loose an arm or be severly injured. After that mishap a massive UPS system was installed capable of running the entire dual projector system for close to 30 min.

Mark

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Monte L Fullmer
Film God

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From: Nampa, Idaho, USA
Registered: Nov 2004

- posted 05-03-2008 05:03 AM      Profile for Monte L Fullmer   Email Monte L Fullmer   Send New Private Message       Edit/Delete Post 
(...not to drift this to a side or off-topic here...)

quote: Charles Greenlee
Actually sounds like a good concept even for 35mm, that way you're not losing leader to that little fold, to slip into the split in the ring, that always wears out.
I used to do it all the time with slipwinding the film on the rings, esp with the STRONG rings and managed to teach a few this trick. It became faster to slipwind than to fight that obnoxious overlap clamp style of this certain rings. The Christie rings are tons better on both slipwinding or slotloading.

Slipwinding came from my carbon arc/changeover days when I would slipwind the film on the takeup reel in the lower magazine.

But, when others began to train downstream, that slipwinding on the ring trick faded away quickly.

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Tristan Lane
Master Film Handler

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From: Nampa, Idaho
Registered: Feb 2002

- posted 05-03-2008 04:43 PM      Profile for Tristan Lane   Email Tristan Lane   Send New Private Message       Edit/Delete Post 
quote: Charles Greenlee
I'm guessing they require the friction of the leader itself to hold it onto the ring? I can imagine having to bring that much leader around to the rewind platter would cause it to end up all over the floor.
The leader never touched the floor. You only pulled as much as you needed. We wound the rings by holding the film in place for a full revolution and by the next half turn, it was bound to the ring. We then spun the takeup platter until the auto-load foil tape was positioned where we wanted it and proceeded to thread the projector. There's so much surface area with 70mm, that only a half turn more after one full wrap secured the film to the ring nicely.

This method is undeniably rougher on the leader than the "twiddle". To overcome this, we added scrap film to the front of the print.

Mark, you see where I'm coming from. The registration pins are so reliable because they are stationary. If the added retraction to them, I would imagine picture steadiness would be greatly affected, even if the tolerances were tight.

EDIT: To add to my comments at the top, I worked in a booth before extended play platters came out. The diameter was small enough that most people could reach the far side of the takeup ring and continue holding the leader to it. I'm guessing this would be difficult with the huge platters in use now.

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Charles Greenlee
Jedi Master Film Handler

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From: Savannah, Ga, U.S.
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- posted 05-04-2008 05:21 AM      Profile for Charles Greenlee   Author's Homepage   Email Charles Greenlee   Send New Private Message       Edit/Delete Post 
Not really. I could hold on to the leader, during its entire revolution.

And my observations about the loads of leader ending up all over the floow, wasn't regarding the "slip winding" as you put it, but more with the slot loading. As with most places around here, and what I was taught, had you pulling the leader out until the 1st splice lined up with the top roller of the platter stand (which was spaced appropriately away for the 7-sec delay), then thread the projector (while probably stepping all over your spooled out leader), then thread back to the rewind platter. Wrapping it around your hand, and carrying it with you, and using the slip winding on the ring seems much much more elegant.

Go IMAX (courtesy of Film-tech) for showing me a better way. Lets hope I find somewhere I can use it. I may end up back at one of the local Carmikes. Though they mostly run digital, some film occasionally, but that's for a different thread. I would love to learn to run large format, if not an IMAX itself. Seems like a bit of work, but well worth it.

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Mark Gulbrandsen
Resident Trollmaster

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From: Music City
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- posted 05-04-2008 08:11 AM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
quote: Tristan Lane
Mark, you see where I'm coming from. The registration pins are so reliable because they are stationary. If the added retraction to them, I would imagine picture steadiness would be greatly affected, even if the tolerances were tight.
Exactly! There are a number of variations on the cam units though in the IMAX stuff. The Iwerks (CDC) cam units are all pretty much the same. When the bearings in the cam unit which are ABEC 7 bearings begin to go out of tolerance you can actually see the problem on the screen as a very slight horizontal jitter. The cam unit operating within tolerance is actually just as important as the fixed pins are. Retracting the pins wouldn't be all that hard to do(like reg pins in a Mitchell camera movement) but keeping them within tolerance and lubricated complicates it immensly. Camera movements have felt pads around each reg pin that hold just enough oil for 1000 feet of film at sound speed.

Mark

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Tristan Lane
Master Film Handler

Posts: 444
From: Nampa, Idaho
Registered: Feb 2002

- posted 05-04-2008 09:02 PM      Profile for Tristan Lane   Email Tristan Lane   Send New Private Message       Edit/Delete Post 
In addition to the tolerance issue, there really wouldn't be a good way to keep the pins lubricated without said lubricant ending up on the film, and then ending up on the field flattener during subsequent runs.

I miss working with those projectors.

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Jesse August
Film Handler

Posts: 58
From: Vancouver British Columbia
Registered: Jul 2003

- posted 05-07-2008 11:10 PM      Profile for Jesse August   Email Jesse August   Send New Private Message       Edit/Delete Post 
Tristan which theatre did you work at?

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Chris Slycord
Film God

Posts: 2986
From: 청주시, 경북도, South Korea
Registered: Mar 2007

- posted 05-08-2008 08:45 AM      Profile for Chris Slycord   Email Chris Slycord   Send New Private Message       Edit/Delete Post 
He's got to be at the OMNIMAX in Portland as there aren't any imax theaters in Vancouver, WA unless a new one's been built and the imax people didn't update their site.

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Tristan Lane
Master Film Handler

Posts: 444
From: Nampa, Idaho
Registered: Feb 2002

- posted 05-08-2008 05:41 PM      Profile for Tristan Lane   Email Tristan Lane   Send New Private Message       Edit/Delete Post 
I haven't operated IMAX in over 5 years. I started as a projectionist at Edwards Boise IMAX, where we had an SR / QTRU setup. I worked for a short time in Spokane at the city's IMAX theater. It was a single Classic projector with a Mark II reel unit.

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