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Author Topic: Drive-in Intermittents Frankie Angel Film Handler Posts: 6 From: Brooklkyn NY USA Registered: Dec 1999 posted 12-04-1999 08:04 AM                        Years ago I was told that Drive-In theatres utilized a special type of intermittent that had a faster pulldown speed than standard intermittents. These "DI" intermittents pulled down the film quicker and then left it in the aperture for a longer interval. The shutters were then cut back so that the interval that closed off the light was short and the interval where the shutter was opened was long. This allowed alot more light to pass to the screen. The idea of course was to get every ounce of light they could onto those 150 foot screens. Is this an old wives tale or do such creatures exist? Seems like a cheaper alternative to bumping up lamphouse wattage if you just need an extra kick, even if you are only running an indoor. Anyone heard of this? ------------------ Frank Angel, Brooklyn Center Cinema www.BrooklynCenter.com  |  IP: Logged Ken Layton Phenomenal Film Handler Posts: 1452 From: Olympia, Wash. USA Registered: Sep 1999 posted 12-04-1999 12:11 PM                     Yes they do indeed exist. Simplex had a special high speed intermittent. They were made in limited quantities and were much more costly. It yielded more light on screen.  |  IP: Logged Stefan Scholz Expert Film Handler Posts: 223 From: Schoenberg, Germany Registered: Sep 1999 posted 12-04-1999 03:01 PM                        Correct, not only Simplex, but also Phillips (Norelco) was a supüplier of such gears. There are only two ways to get more light on screen, on is the optical way, the use of light sources, which offer a higher density of light (candelas per sq inch). This, is why rotating carbons wirth vent systems were used on larger arclamps. They were limited to a maximum of about 225 A or so. With Xenon, the maximum light efficiency is archiueved with 35 mm film with the 4200 W lamp, the 7k's gap is about 1/2", which is close to the heigh of film, and does not give any light effectivity. On the other hand the visible spectrum is intense enough to endanger the film. So, for large screen presentations, other measures must be taken. On is improved shutter design (XtraLight), and a shorter film travel time, thus archieved with accelerated intermittents. But there's another limit. The accelaration of film must stay within certain values, not to mechanically overload film. (No longer with polyester). As theese intermittens still used standard 4 wing maltese crosses, they had to use a gear train inbetween. Therefore registration stability was not as good as with a standard type, but the gain abiout 25% effectivity and the use in special venue type (sorry, drive in is considwered a special venue operation) this was acceptable.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 12-04-1999 03:05 PM                     The phillips FP7 was also available as the super 7 with a highspeed movement It was extremely noisy but also produced lots of light. Brenkert BX 100's also had a highspeed movement for telecine work 5:1 Also the powers movement was high speed Usually they didn't gear the pull down but used a offcentred maltese cross so that it bobed internally during pull down to increas the dwell time radius area  |  IP: Logged David Johnson Film Handler Posts: 54 From: Melbourne Vict Australia Registered: Oct 1999 posted 12-05-1999 01:41 AM                     The High speed movments were also used on Cinerama. David  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 12-08-1999 10:04 AM                     I have had quite a bit of experience with the Simplex D.I. high speed movement. I have used them on portable jobs to allow for using a smaller lamphouse and bulb to acheive the same amount of light I could have with a much larger lamp. Recently I installed a pair of them in a double drive in in northern Indiana that could only run a max 3K lamp due to having single phase power. The improvement in brightness was far greater than if we could have gone to a 4KW lamp. I got the pair of movements from Charlie Wolk and he had at least several pair at the time. I have also noticed drastic improvement in picture steadiness and sharpness when using a high speed movement. Everyone that has seen the resultant image agrees but no one has really been able to explain why this happens. I was notaware that Cinerama used a high speed pull down. I have reworked quite a number of Cinerama machines but have never run into one that has this yet. I did however have an unused Cinemascope 55 movement and this was definately a high speed job and was done quite differently from the Simplex.  |  IP: Logged

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