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» Film-Tech Forum   » Operations   » Large Format Forum   » 5/70? 8/70? 15/70? (Page 1)

 
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Author Topic: 5/70? 8/70? 15/70?
Richard Greco
Phenomenal Film Handler

Posts: 1180
From: Plant City, FL
Registered: Nov 2003


 - posted 01-15-2005 01:41 AM      Profile for Richard Greco   Email Richard Greco   Send New Private Message       Edit/Delete Post 
Can someone explain these numbers to a 35mm guy? I know the 70 means 70 mm, but what do the rest mean?

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Paul Mayer
Oh get out of it Melvin, before it pulls you under!

Posts: 3833
From: Albuquerque, NM
Registered: Feb 2000


 - posted 01-15-2005 02:18 AM      Profile for Paul Mayer   Author's Homepage   Email Paul Mayer   Send New Private Message       Edit/Delete Post 
The number of perfs defining that dimension of the film frame. So 570 is five perfs high, 870 is eight perfs high, 1570 is 15 perfs wide (1570 runs horizontally).

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Monte L Fullmer
Film God

Posts: 8161
From: Nampa, Idaho, USA
Registered: Nov 2004


 - posted 01-15-2005 02:57 AM      Profile for Monte L Fullmer   Email Monte L Fullmer   Send New Private Message       Edit/Delete Post 
quote: Paul Mayer
870 is eight perfs high, 1570 is 15 perfs wide (1570 runs horizontally).

or...5/70 is your usual 70MM, 8/70 is the vertical film run SuperScreen, and the 15/70 is the IMAX/OmniMax presentation.

Here's some pics of 5/70 and 15/70 IMAX. The 5/70 is from "Dr. Dolittle" and the 15/70 is from that Space Shuttle show (forget the title).

the 5/70

 -

the 15/70

 -

Sound for the 5/70 is on the magnetic tracks containing the standard six channels, whereas the 8/70 and the 15/70 uses a digital sound dubber that runs in sync with the film.

-thx Monte

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Dick Vaughan
Phenomenal Film Handler

Posts: 1032
From: Bradford, West Yorkshire, UK
Registered: Jul 2000


 - posted 01-15-2005 04:45 AM      Profile for Dick Vaughan   Author's Homepage   Email Dick Vaughan   Send New Private Message       Edit/Delete Post 
5 /70 prints can also carry DTS code in place of the mag tracks and have in the past had digital soundtracks (CDS)

8/70 and 15/70 can also be synchronised with 35mm mag tracks, 1/2" 8 track,multi CD ( IMAX DDP) and DTS.

And I am sure that Messrs Hill and McLeod can add to this

In fact Phil probably synchronised 1570 to Vitaphone discs in his youth [Big Grin]

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Richard Greco
Phenomenal Film Handler

Posts: 1180
From: Plant City, FL
Registered: Nov 2003


 - posted 01-15-2005 10:58 AM      Profile for Richard Greco   Email Richard Greco   Send New Private Message       Edit/Delete Post 
Thanks Guys, now I understand.

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Darryl Spicer
Film God

Posts: 3250
From: Lexington, KY, USA
Registered: Dec 2000


 - posted 01-15-2005 11:51 AM      Profile for Darryl Spicer     Send New Private Message       Edit/Delete Post 
....and if you notice on the 15/70 example strip the jagged cut on the left side. This is done to reduce the tendancy of the film pulling away from the splice do to the tension caused by the speed at wich the film flows.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 15887
From: Bountiful, Utah
Registered: Jun 99


 - posted 01-15-2005 12:53 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
quote: Darryl Spicer
This is done to reduce the tendancy of the film pulling away from the splice do to the tension caused by the speed at wich the film flows.

Actually it allows the film to flex without making a sharp bend as a straight splice might do. This is very important in a rotor based projector of any gauge where the rolling action of the film might cause a straight splice to bend 90 degrees and cause a resultant pile up in which severe damage may result to the projectors claw mechanism.

Mark

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Adam Martin
I'm not even gonna point out the irony.

Posts: 3632
From: Dallas, TX
Registered: Nov 2000


 - posted 01-15-2005 01:17 PM      Profile for Adam Martin   Author's Homepage   Email Adam Martin       Edit/Delete Post 
Claw mechanism? What awful projector uses a claw mechanism?

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Dave Macaulay
Phenomenal Film Handler

Posts: 1939
From: Toronto, Canada
Registered: Apr 2001


 - posted 01-15-2005 03:38 PM      Profile for Dave Macaulay   Email Dave Macaulay   Send New Private Message       Edit/Delete Post 
The "claw mechanism" is used in Imax 15/70 projectors (I'm not sure about the new one, but it probably does) and in all the other large format rolling loop systems I've seen. This claw does not do the frame advance, the rolling loop takes care of that. The film is set on stationary registration pins around the projection aperture when the loop rolls past; this changes frames quite rapidly. As well as having a loop formed and dissipated 24 times a second, the film is moving through the projector at 337.5 feet/min. Just laying it onto the registration pins would require the film's mass to be decelerated by the registration pins - and would damage the registration perforations slightly. After repeated passes the accumulated damage would make the screen image quite shaky horizontally. To prevent damage to the registering perforations a "claw arm" engages film perfs a few away ("before" if you look at the projector but "after" in the sense of film time) from the leading registration perfs. The arm is actuated by a cam system so that the pins enter the perforation at the same speed as the film motion, then decelerate relatively gently until the film is almost stationary as the registration pins are engaged. A properly adjusted Imax projector will run a film loop for thousands of passes with no perforation damage.

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Adam Martin
I'm not even gonna point out the irony.

Posts: 3632
From: Dallas, TX
Registered: Nov 2000


 - posted 01-15-2005 08:18 PM      Profile for Adam Martin   Author's Homepage   Email Adam Martin       Edit/Delete Post 
Oh ... you mean the CAM and CAM ARM. I have never heard anyone call it a "claw mechanism", so I read it to mean a claw mechanism that advances the film, such as in an camera. (And let me tell you ... the claw mechanism in an Imax camera is something to behold!)

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Phil Hill
I love my cootie bug

Posts: 7595
From: Hollywood, CA USA
Registered: Mar 2000


 - posted 01-16-2005 07:48 PM      Profile for Phil Hill   Email Phil Hill       Edit/Delete Post 
Adam: I cannot believe it! You are soo naive! Dave said it best and eloquently explained what was meant by the term "claw" and its function as it pertains to a rolling-loop projector.

I'll have to go and look at my copies, but I believe that it is referred to as the "deceleration cam, arm, and CLAW" in the patent as well.

Gosh! For a mod, you sure are a dumbass sometimes! HA!

(Am I banned yet?)

Hugs,

>>> Phil

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000


 - posted 01-17-2005 01:56 PM      Profile for John Pytlak   Author's Homepage   Email John Pytlak   Send New Private Message       Edit/Delete Post 
Just a few of the US Patents for the IMAX projection system:

U.S. Patent Documents
3494524 Feb., 1970 Jones
3600073 Aug., 1971 Shaw
3794415 Feb., 1974 Jones
3944349 Mar., 1976 Jones
4039256 Aug., 1977 Teeple et al.

PAT. NO. Title
1 5,050,985 Film deceleration unit
2 4,997,270 Projected image alignment method and apparatus
3 4,993,828 Camera and method of producing and displaying a 3-D motion picture
4 4,971,435 3-D motion picture projection apparatus
5 4,957,361 Method of producing and displaying a 3-D motion picture
6 4,441,796 Film support element assembly
7 4,406,519 Projection screen assembly
8 4,365,877 Field flattener lens element assembly
9 4,114,996 Inlet guide structure for rolling loop film transport mechanism

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Phil Hill
I love my cootie bug

Posts: 7595
From: Hollywood, CA USA
Registered: Mar 2000


 - posted 01-17-2005 03:20 PM      Profile for Phil Hill   Email Phil Hill       Edit/Delete Post 
Oh yes. Thanks John for reminding me. [Mad] [Wink] [Big Grin] I'd hate to say how many times I was in court and/or gave depositions about those patents. Ummmm, of why we were not infringing. [Big Grin]

The one that still kills me to this day and I still have nightmares over is: 4,365,877 Field flattener lens element assembly. I could NEVER figure a way around it without using a septum! DAMN! [Big Grin]

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Randy Stankey
Film God

Posts: 6355
From: Erie, Pennsylvania
Registered: Jun 99


 - posted 03-16-2005 05:28 PM      Profile for Randy Stankey   Email Randy Stankey   Send New Private Message       Edit/Delete Post 
quote: Dave Macaulay
To prevent damage to the registering perforations a "claw arm" engages film perfs...
So, this cam/claw mechanism operates in similar fashion to the claw in a sewing machine that advances the fabric under the needle, except in reverse? (It slows the film down rather than pushing it along.)

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Thomas Dieter
Expert Film Handler

Posts: 234
From: Yakima, WA
Registered: Jun 2004


 - posted 03-16-2005 07:43 PM      Profile for Thomas Dieter   Email Thomas Dieter   Send New Private Message       Edit/Delete Post 
WOW, I have to say that all this information that everyone has just posted, just made me want to operate an 870, and a 1570 projector more than ever. I've watched 1570 film being threaded in an OmniMax projector before, and even had the guts to ask to come in and look at the projector(I got denied). I think was it is that facinates me about this film is the fact that it is so large, and the way it is handled is amazing.

The zigzag splice? I under stand how it works and all, and it's a great idea. What my question is, does the appature plate cut out the zigzaged area so that the film doesn't look to bleed on one side of the screen, or do you have to take and cut your splice back one tooth? Also to go with that question, would a / spice work too? The drive in theatre that I use to work for had a splicer that was able to make | and / splices. And this should go in another thread and what not, but beings that I've touched on it already, what's the purpose of the / splice?

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