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» Film-Tech Forum   » Operations   » Film Handlers' Forum   » High Speed Pulldown (Page 1)

 
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Author Topic: High Speed Pulldown
Mark Gulbrandsen
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Posts: 16146
From: Bountiful, Utah
Registered: Jun 99


 - posted 08-23-1999 06:36 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
Here's one for you to munch on...... I have donea few past rental jobs with Simplex X-L's that had the high speed movements in them. My use for them was primarily one of higher light effeniency and to be able to utilize a smaller lamphouse on certain rental jobs. The heads ran great, a bit noisier with acetate, but not much noisier with Estar base films. However the one thing that everyone was in agreement on was that the projected image appeared much sharper and steadier than when projected with a regular speed movement. Why?

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Christopher Seo
Jedi Master Film Handler

Posts: 530
From: Los Angeles, CA
Registered: Jun 99


 - posted 08-24-1999 05:15 AM      Profile for Christopher Seo   Email Christopher Seo   Send New Private Message       Edit/Delete Post 
I have more questions than answers, but oh well...

What kinds of films were these? Specialty ones? Scientific films? Were they actually shot at higher frame rates or just specially prepared to be projected at them? And what was the frame rate during projection?

How did the high-speed movement differ from the regular one.... was it a special-order type of part?

I have some speculatory ideas as to your question... first of all, did you try testing the high-speed movement at normal frame rates to try out the steadiness? Perhaps the high-speed movement was simply all-around better quality. I don't suppose it would be wise to try a regular movement at higher-than-normal speed, but it would be interesting to judge the resulting performance.

I think this topic gets at the question of, What actually causes a motion picture to be unsteady? Does the intermittent pull down each successive frame slightly out of registration with the previous one, or does the film have time to 'drift' in the gate in between pulldowns? If the latter is the case, then perhaps at higher frame rates each frame has less time to drift between pulldowns.

As for the sharpness, it probably has to do with the fact that grain is less apparent since each particular grain of each particular frame is being replaced faster, thus improving the illusion that the enlarged clumps of dye we view is more like a smooth continuum of color.

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John Pytlak
Film God

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


 - posted 08-24-1999 09:46 AM      Profile for John Pytlak   Author's Homepage   Email John Pytlak   Send New Private Message       Edit/Delete Post 
AFAIK, the Simplex high speed intermittent used an additional lever between the drive shaft and the cam, such that the cam pin drove the starwheel faster during the pulldown cycle. Since less time was spent pulling the frame into position, wider shutter openings could be used without having travel ghost, increasing light efficiency. They were usually used for drive-ins and very large screen applications. High speed intermittents were noisier and put more stress (higher acceleration) on the film perforations, but were theoretically capable of comparable steadiness to "normal" intermittents.

Perhaps the improved sharpness you observe is because the film frame is illuminated for a longer time, allowing it to come to a more stable focus position, with less focus flutter.

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John Pytlak

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Brad Miller
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From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99


 - posted 08-24-1999 02:06 PM      Profile for Brad Miller   Author's Homepage   Email Brad Miller       Edit/Delete Post 
To answer Christopher's questions...the high speed intermittent still runs normal film at 24FPS. All it does is spin the intermittent sprocket faster, so it can sit still longer...giving narrower shutter blades so there is more "picture" and less "black" projected.

Since I've never worked with one of these, I'd have to go with John's theory on the improvements. I've always wanted to try one, though. They're supposed to be hell on film.

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Jason Burroughs
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From: Allen, TX
Registered: Jun 99


 - posted 08-24-1999 09:22 PM      Profile for Jason Burroughs   Email Jason Burroughs   Send New Private Message       Edit/Delete Post 
With the advent of polyestar film is that so much of an issue now? I can see how an acetate print would react badly to the increased accelleration. How would the increased time of light affect print burning? I would think that lamp focus and IR filtering would be even more important since the light would be on the film longer.

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John Pytlak
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From: Rochester, NY 14650-1922
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 - posted 08-25-1999 09:45 AM      Profile for John Pytlak   Author's Homepage   Email John Pytlak   Send New Private Message       Edit/Delete Post 
Polyester prints are much less prone to perforation damage such as tearing, but excessive tension over a sprocket can still deform (stretch) the perfs. SMPTE Recommended Practice RP106-1994 "Film Tension in 35-mm Motion-Picture Systems..." recommends no more than 4.4 Newtons (16 ounces) of tension to avoid perforation damage.

As far as radiant energy, if you are trying to get SMPTE standard 16 footlamberts (55 candelas per square metre) on the screen, a shutter with higher efficiency would allow you to use a lower power level (as noted in the original posting). The amount of energy going through each 24fps frame is the same if the screen luminance is constant. Going to a higher frame rate (e.g., 30fps) does reduce the energy on each frame. Going to a larger format (e.g., 70mm) "spreads out" the energy over a larger area, reducing the risk of heat damage.

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John Pytlak

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Mark Gulbrandsen
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From: Bountiful, Utah
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 - posted 08-25-1999 10:18 AM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
Sorry guys for not getting back sooner. One instance was for the Cinema Borealis outdoor screening and the showing of "Ran"(check out how bright the picture was on the picture warehouse page). Speed was standard 24fps, illumination was from a Christie 4KW retrofitted with a kneisley xenex ll reflector. A second occasion was for Amoco's bitrhday celebration in Atlanta. In both instances with a normal machine I was able to use what would have been the next size bulb down in size. Both screens were matte white. Recently I aquired two high speed intermittants from Charlie Wolk and installed them in a twin drive in near Bass Lake,Indiana. The same results were noticed there as well. Brighter picture, better focus and steadiness. They now have the illumination that a 4kw bulb would provide, but by using a 3kw lamp instead. The theater only had 3 phase available, so couldn't run a 4kw if they wanted. The ratio for the high speed pull down is 5 to 1 where a standard intrmittant is 3 to 1. With the advent of estar base film there are no problem in using these movements. The film can take the small extra stress that acetate didn't care for.

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John Pytlak
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From: Rochester, NY 14650-1922
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 - posted 08-25-1999 12:27 PM      Profile for John Pytlak   Author's Homepage   Email John Pytlak   Send New Private Message       Edit/Delete Post 
The durability of polyester film, and the need for more light on huge screens, may bring a resurgence of high speed intermittents. The comments on better sharpness and steadiness are an unexpected pleasant surprise.

Is anyone still making new "high speed" or "fast pulldown" intermittents? Or are they only available as rebuilt units? Which ones are still in good supply? What is the narrowest shutter blade (degrees) that can be used without having any travel ghost? (i.e., If a normal 4:1 needs 90-degrees, does a 5:1 only need 72-degrees?).

No doubt they are noisier. But how reliable are they (how often do they need to be rebuilt)? Are parts readily available? Who/where is the best place to purchase them, or get them rebuilt?

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John Pytlak

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Mark Gulbrandsen
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From: Bountiful, Utah
Registered: Jun 99


 - posted 08-25-1999 01:55 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
Yes, I believe the shutters were 72 degrees. And in a drive in situation you might even go to near 80 degrees with a little travel ghosting as is usual in most D.I.s. I got a pair from Wolk. I think he has a ton of parts for them as he has converted a bunch to regular pull down. The Simplex uses the same star wheel, but has a short shaft special cam and driver assembley. Give Norm a call and see if he has any kicking around. They were a bit noisier, especially with acetate film, but they are alot quieter with estar film running in them. They have been running in the D.I. in Indiana now for 3 years with no problems and no film breaks. I doubt that any will go back into production. It was special order way back when......

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John Pytlak
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From: Rochester, NY 14650-1922
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 - posted 08-26-1999 08:12 AM      Profile for John Pytlak   Author's Homepage   Email John Pytlak   Send New Private Message       Edit/Delete Post 
Mark ---
Did you really mean to say that for drive-in applications (where a bit of travel ghost may be tolerated to get more light on the screen), high speed movements are used with 80-degree shutter blades? Wouldn't the blade be smaller than the 72-degree theoretical limit for a 5:1 high speed intermittent, maybe as narrow as about 65-degrees?

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John Pytlak

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Gordon McLeod
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From: Toronto Ontario Canada
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 - posted 08-26-1999 01:51 PM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
The norelco fp7 was also available as the super7 with a high speed movement and a very large diametre narrow bladed shutter it averaged in at around 70% light efficient

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Mark Gulbrandsen
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Posts: 16146
From: Bountiful, Utah
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 - posted 08-26-1999 05:33 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
Yes John,

You're right. Thanks!!

Mark

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RICK HAMILTON
Film Handler

Posts: 28

Registered: Aug 1999


 - posted 08-26-1999 10:24 PM      Profile for RICK HAMILTON   Email RICK HAMILTON   Send New Private Message       Edit/Delete Post 
"The theater only had 3 phase available, so couldn't run a 4kw if they wanted." I'm confused. are there more than 3 phases?
rick

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Rick Long
Jedi Master Film Handler

Posts: 759
From: Toronto, Ontario, Canada
Registered: Nov 1999


 - posted 08-31-1999 05:31 PM      Profile for Rick Long   Email Rick Long   Send New Private Message       Edit/Delete Post 
Like maybe you need 1 phase per Kw, eh?

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RICK HAMILTON
Film Handler

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Registered: Aug 1999


 - posted 08-31-1999 10:37 PM      Profile for RICK HAMILTON   Email RICK HAMILTON   Send New Private Message       Edit/Delete Post 
IS THAT HOW IT WORKS??? DOES THAT MEAN THAT I NEED 4 AND A HALF PHASES TO RUN A 4.5K BULB? SHOULD I HAVE ELECTRICIANS COME OUT AND REMOVE THE EXTRA PHASES IN OUR SMALL BOOTHS? THINK OF ALL THE POWER WE WILL SAVE IN OUR 1K HOUSES!!!!THANK YOU!!!

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