|
|
This topic comprises 6 pages: 1 2 3 4 5 6
|
|
Author
|
Topic: IMAX Basics
|
Jerry Chase
Phenomenal Film Handler
Posts: 1068
From: Margate, FL, USA
Registered: Nov 2000
|
posted 08-12-2001 09:11 PM
I still have the illusion that the rotor and the film are travelling at the same speed because there are no frame indications on the grey line you use to represent the film. Also, the cam seems to sit still rather than release the film, and there are no registration pins. Also, what prevents the film from hitting the (sharp?) edge of the rotor gap?Don't get me wrong, you've got a good illustration for the mechanically inclined, I just wonder if it can be made to show the concept to the lay public by adding just a little more detail. Bravo for taking on the project in any event.
| IP: Logged
|
|
|
|
|
|
Phil Hill
I love my cootie bug
Posts: 7595
From: Hollywood, CA USA
Registered: Mar 2000
|
posted 08-12-2001 11:06 PM
Dave is correct on the purpose and use of the compressed air jets...to stop buckling of the center of the film and thus damaging the picture area. The jets are located on each rotor segment's leading edge at the loop gap. The air is pulsed at just the right time and for a specific amount of time else it would damage the film by pushing the loop against the trailing edge of the prior segment or collapse the loop. This is what gives the rolling loop the "Choo Choo" sound of a steam train engine when starting.
As far as the linear speed of the film relative to the rotor: The film enters the rotor gap at the input sprocket at a constant speed, at the same time it is stopped at the aperture for projection, and at the same time it is being withdrawn by the exit sprocket at a constant speed.The loop being formed on the input side of the aperture, and the loop collapsing on the output side makeup the film-speed difference between the constant speed spockets and the stopped (projected) frame.
So the film actually "slides" along the rotor at various speeds between the constant speed sprockets and the frame stopped on the register pins. Iwerks "Linear Loop" technology is very different than the "Rolling Loop" technology and has it's own patents and Academy Award. Iwerks 1570 projector is the Rolling Loop technology and the Linear Loop is used in the 435, 835, 570, 870, and 1070 formats. >>> Phil
| IP: Logged
|
|
Adam Martin
I'm not even gonna point out the irony.
Posts: 3686
From: Dallas, TX
Registered: Nov 2000
|
posted 08-13-2001 01:06 AM
Stop breakin' my balls, Jerry!  Use the animation as a "general idea" sort of thing. Here are the patents Gordon mentioned above. These are in .pdf format and you need Adobe Acrobat Reader to view these, but if you've visited the manual warehouse, you already knew that. 3,600,073 Rolling Loop Film Transport Mechanism [18 pages, 1256 KB] August 17, 1971: A rolling loop mechanism for transporting photographic film through a motion picture apparatus. 3,794,415 Rolling Loop Transport Mechanism [7 pages, 395 KB] February 26, 1974: A mechanism for transporting photographic film past an aperture in a projector, camera or other motion picture machine. 4,114,996 Inlet Guide Structure for Rolling Loop Film Transport Mechanism [6 pages, 433 KB] September 19, 1978: Inlet guide structure is provided having complementary outer and inner guides which are adapted to receive film from a drive sprocket of a rolling loop film transport mechanism and to guide the film inwardly towards a path defined between the stator and the rotor of such a mechanism.
| IP: Logged
|
|
|
|
|
|
|
|
|
|
|
|
Dave Macaulay
Film God
Posts: 2321
From: Toronto, Canada
Registered: Apr 2001
|
posted 08-14-2001 12:17 PM
The theatre with the ruined print, no light, and cassette hand sync sound was (is?) in a rather poor country where the President funded major capital projects (like Omnimax theatres) in order to (supposedly.. (I hate libel suits...)) skim off as much of the funding as possible. Then, little or no operating funding. The IMAX service contract expired. The staff, government employees, were somewhat resented by the state government stuck with them after the federal project was completed and if they had to close the theatre, they were unemployed.
Desperate situation, no?
I understand their predicament and they did a hell of a job with what they had. They have also stripped the keys (3/4" keys on 2" shafts...) on the main projector elevator drive sprockets and destroyed one sprocket, and had a replacement made by hand that was quite nice. (The interlocks failed and one guy in a side room was holding the 10hp elevator motor contactor in while another watched and yelled when to stop! Needless to say someone didn't stop, and the projector came down rather quickly. Soon there was a design change incorporating a slip clutch in the motor.)My point about showmanship is more about the "premium" 35MM theatres with stadium seating, digital sound, giant screens etc. We all know that the performance can be quite awful- from sound dropouts, blown channels, maladjusted/flickering/dim light to dirt encrusted prints or a screen decorated with coke and gummi bears. Does anyone ever tell the customers there's a problem? Or, as I expect, quietly deal with the occasional complaint while counting the money?
I was at an AMC show (I only go to the big houses with rear exits because it's easy for me to go in the booth and fix focus or other simple problems) and the operator had to focus severely at startup. I knew the Millennium gate was in to far and would snap into index soon. It did, at the "feature" snipe. I waited to see what happened, as about 200 people sat on their butts. For 10 minutes. I know someone would have complained eventually, of course (hope so anyhow). I went up and focused it. (OK, I turned the sound up a bit too)
This isn't to complain about the operator, AMC, the projector, or anything like that. Just to illustrate that most people don't complain, they will endure a really bad show. BUT they won't be coming back and parting with $11.00 very soon.
"The Show Must Go On" drives people away to the video store.
If told there is a technical problem and the film is dirty, the sound is not 100%, or whatever, I might decide not to go in but I would appreciate that they respect me and want me back, and I would go back. I've only ever seen that kind of notice in changeover houses with a dead machine, letting patrons know there will be breaks between reels. The crappers have little papers that have the time of the last inspection.
How about ones with "last lamphouse/illumination check" "last A- / B- chain alignment" at the box office window?
| IP: Logged
|
|
Christopher M. Belch
Film Handler
Posts: 24
From: Canton, Michigan, USA
Registered: Apr 2001
|
posted 08-14-2001 03:15 PM
After working in an imax theater for about two years (im currently training to be a projectionist) i have become accustomed to the perfect presentation, or at least something close to it. Now, i am not trying to knock 35 mm, cuz there are some great projectionist out there, they are just becoming hard to find. As dave mentioned, most theater owners couldnt care less about their presentation. A few months ago i watched a 3 foot dust ball on the screen for over an hour until the movie was over, and no projectionist every came to clean it. WHen i complained to the manager, of course it was "sorry, heres your money back, have a nice day." Of course, i had the same problem next time i came back, same get your money back, yet no changes. I think the problem is, it is cheaper to shut up the few people who know the difference and give then their money back than to fix the problem and hire a few more staffers to work the projectors. Even at our imax theater we are constantly under pressure from the operations staff to "hurry the film up, we are running five minutes behind." Thankfully, the technical staff wont give in to the demands, and continues to un the booth for a perfect (or close to it presentation, even if it means falling a few minutes behind schedule. ANd the biggest problem is? Most people dont notice.(hope i did ok, this is my first post, well actually third, but the other two didnt seem to work.)
| IP: Logged
|
|
Gordon McLeod
Film God
Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99
|
posted 08-15-2001 10:04 AM
Here are some more Rolling loop, Cam unit and Field Flatner patents
4,365,877 4,039,256 5,048,948 5,050,985 5,561,483
2 of these are non IMAX patents
| IP: Logged
|
|
|
|
|
|
|
|
All times are Central (GMT -6:00)
|
This topic comprises 6 pages: 1 2 3 4 5 6
|
Powered by Infopop Corporation
UBB.classicTM
6.3.1.2
The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion
and agrees to release the authors from any and all liability.
|
Home
Guess that was why I was a D.M., or maybe I learned it from being a D.M. Anyway, I didn't mean to do that and I know you put a lot of work into the animation and should be proud of it.
Printer-friendly view of this topic