Film-Tech Cinema Systems
Film-Tech Forum


Post New Topic  Post A Reply
my profile | my password | register | search | faq & rules | forum home
  next oldest topic   next newest topic
» Film-Tech Forum   » Operations   » Large Format Forum   » IMAX Basics (Page 1)

 
This topic comprises 6 pages: 1  2  3  4  5  6 
 
Author Topic: IMAX Basics
Brian Hogan
Expert Film Handler

Posts: 119
From: Charlotte, North Carolina, USA
Registered: Jul 2001


 - posted 08-06-2001 10:09 PM      Profile for Brian Hogan   Email Brian Hogan   Send New Private Message       Edit/Delete Post 
I frequent a web site that tries to explain how stuff works. Its kinda neat and contains pics and vids for many topics. They recently added an article that explains the bare basics of how IMAX works. The article also contains links to some other pages dealing with theatres and projection. Check it out at http://www.howstuffworks.com/imax.htm ... I'm out.

 |  IP: Logged

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

Posts: 3653
From: Dallas, TX
Registered: Nov 2000


 - posted 08-07-2001 01:04 AM      Profile for Adam Martin   Author's Homepage   Email Adam Martin       Edit/Delete Post 
Not that it's a bad article, but it's basically just a fluff piece, made to impress the masses. There are a few issues with the article ...

quote:
IMAX films are shot and printed on huge film stock that is completely unique in the industry.
Wrong. Standard 65mm camera negative and 70mm print stock is used. It's *how* it's used that's unique. It's usually just great Kodak Vision stock.

quote:
A vacuum system sucks each image onto a piece of glass in front of the lens so that the image is oriented perfectly in front of the lens.
And the registration pins might just have something to do with that, too.

quote:
The shutter opens for a longer period of time than on a normal projector in order to let more light through.
Nit picking here, the nature of rolling-loop film movement and registration allows for a more efficient use of light.

quote:
The bulb for the projector is a 15,000-watt, water-cooled xenon unit.
An unmodified classic (2D and Dome) has a 12,000-watt water-cooled lamp; a modified classic (2D and Dome) has a 15,000-watt water-cooled lamp; a GT (3D) has two 15,000-watt water-cooled lamps; and an SR has just a 7,000-watt air-cooled lamp.

quote:
an IMAX projector weighs over 2 tons (2,000 kilograms)
Again, the GT is over 2 tons; the SR is 1300 pounds; don't know the classic off-hand.

quote:
Not only are the films shot on IMAX's 15/70 film stock, ...
Again, Imax doesn't make the film stock.

quote:
For example, the dinosaurs in "T-REX" have five times the detail of the dinosaurs in the Jurassic Park movies. This means that it takes five times more computer power to render each "T-REX" image, and five times the storage space.
Yeah, but the T-Rex is only on-screen for 2 minutes out of 45! Really!

quote:
The camera is immense. It weighs 240 pounds
The 3D camera weighs 240 pounds. There are several lightweight 2D models such as the one used for Everest.

quote:
there are only two IMAX 3-D cameras in the world,
I know Iwerks has 2D cameras ... don't they have 3D cameras, too?

quote:
The camera is also very noisy -- it sounds like a chain saw when it is running.
Blimping does help somewhat, but not completely. I'll give them this one.

quote:
everything is photo-real
That just seems like a really stupid thing to say about something you are photographing.

Okay, I'm done. Now everyone go and search the forums for topics where we've discussed the Imax format for the anti-fluff info.

[ 03-03-2007, 03:11 PM: Message edited by: Adam Martin ]

 |  IP: Logged

Brian Hogan
Expert Film Handler

Posts: 119
From: Charlotte, North Carolina, USA
Registered: Jul 2001


 - posted 08-07-2001 01:14 AM      Profile for Brian Hogan   Email Brian Hogan   Send New Private Message       Edit/Delete Post 
yeah, well i knew that just about anyone reading that article from here would have a field day with it. im glad i could help


 |  IP: Logged

Randy Stankey
Film God

Posts: 6410
From: Erie, Pennsylvania
Registered: Jun 99


 - posted 08-07-2001 05:29 AM      Profile for Randy Stankey   Email Randy Stankey   Send New Private Message       Edit/Delete Post 
That page is OK but I agree with you. It's mostly fluff. It's nice and all but to somebody who has some knowledge on the subject there's not much that we don't already know.

What I REALLY want to see is a picture of the IMAX projector. Nothing too fancy... just something like, "The film goes in here, through this doohicky, around this thingamabob then comes out here. (Or whatever.)

Is there some kind of patent/trade secret thing that prevents people from showing that?

 |  IP: Logged

Michael Brown
Phenomenal Film Handler

Posts: 1518
From: Bradford, England
Registered: May 2001


 - posted 08-07-2001 06:22 AM      Profile for Michael Brown   Email Michael Brown   Send New Private Message       Edit/Delete Post 
Slightly off topic but i thought the SDDS diagram was interesting:

Click Here

(remember to click on the red oval SDDS icon)

with the left and right channels on the walls. interesting


 |  IP: Logged

Tao Yue
Expert Film Handler

Posts: 209
From: Princeton, NJ
Registered: Apr 2001


 - posted 08-07-2001 07:17 AM      Profile for Tao Yue   Author's Homepage   Email Tao Yue   Send New Private Message       Edit/Delete Post 
I believe that diagrams in HowStuffWorks.com are done separately from the articles, so there are often inconsistencies even when the author of the article has communicated with the illustrator.

In this case, it seems like there was absolutely no communication whatsoever -- don't just look at the SDDS -- that diagram was used throughout the movie sound article. Not only doesn't it show the additional screen channels for SDDS; it also seems to believe that Dolby Stereo has only two channels and has completely left out the left and right surrounds. But I suppose we can't expect all illustrators to be experts on motion picture sound.

------------------
Tao Yue
MIT '04: Course VI-2, Electrical Engineering and Computer Science
Projectionist, MIT Lecture Series Committee

 |  IP: Logged

John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999


 - posted 08-07-2001 08:20 AM      Profile for John Walsh   Email John Walsh   Send New Private Message       Edit/Delete Post 
Do't forget, though, people going to this are probably not looking for *very* techinal descripions. Also, I think the site is geared for younger people; it's better not to scare them away!

 |  IP: Logged

John Pytlak
Film God

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


 - posted 08-07-2001 11:05 AM      Profile for John Pytlak   Author's Homepage   Email John Pytlak   Send New Private Message       Edit/Delete Post 
The excellent "classic" technical papers on the birth of the IMAX film system are:

"The Rolling Loop -- A New Concept of Film Transport", by P. R.(Ron) W. Jones, SMPTE Journal, January 1968, pages 21-23

"Film Dynamics of a Rolling-Loop Film-Transport System", by William C. Shaw, SMPTE Journal, September 1970, pages 778-782

"New Large-Screen and Multi-Image Motion-Picture System", by William C. Shaw, SMPTE Journal, September 1970, pages 782-787

Technical achievements like this make you proud to be a member of the SMPTE.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion


 |  IP: Logged

Brian Hogan
Expert Film Handler

Posts: 119
From: Charlotte, North Carolina, USA
Registered: Jul 2001


 - posted 08-07-2001 06:18 PM      Profile for Brian Hogan   Email Brian Hogan   Send New Private Message       Edit/Delete Post 
john said something about the articles being geared towards younger people. that may be true, but i think they just use very simple and basic explanations for things so its easier to grasp the concept, rather than try to understand all inner workings of everything.

other things he explains on the site can be somewhat more complex. a question was submitted concerning what makes super glue so super ( http://www.howstuffworks.com/question695.htm ). he went into the main chemical makeup and how it reacts to make polymer bonds and what not. i mean, its basic chemisty but if you know nothing about chemistry in the first place, then its a good thing to get a brief explanation.

ok, time to get some chow.

 |  IP: Logged

Joe Redifer
You need a beating today

Posts: 12859
From: Denver, Colorado
Registered: May 99


 - posted 08-07-2001 06:23 PM      Profile for Joe Redifer   Author's Homepage   Email Joe Redifer   Send New Private Message       Edit/Delete Post 
Randy-

I don't think that there are patents/whatever preventing people from showing the IMAX projector. Direct your 56k modem to the "VIDEOS" section of this site and click on OMNI THEATER. Be sure to download the big 139 meg Quicktime and you will see the IMAX (actually OMNIMAX) projector in all its glory.

 |  IP: Logged

Mark Gulbrandsen
Resident Trollmaster

Posts: 16112
From: Bountiful, Utah
Registered: Jun 99


 - posted 08-07-2001 11:21 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
Hey John,
I have always wondered where one can get those back articles that appeared in the old SMPTE journals. The only library I know of that has old journals is in Champaign IL, at U of I Grainger Technical Library. And indeed they have themm that go way way back into the 30's. Any insight would be appreciated.
Mark @ GTS

 |  IP: Logged

John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999


 - posted 08-07-2001 11:31 PM      Profile for John Walsh   Email John Walsh   Send New Private Message       Edit/Delete Post 
SMPTE is working on scanning issues and making them avaiable as pdf's. Right now, there's only a few, and I think you have to be a member. Big libraries may have issues, but not many.

If it's just a few articles, I can send them to you. I have some issues, but only back to 1945 (SMPE!).

 |  IP: Logged

Randy Stankey
Film God

Posts: 6410
From: Erie, Pennsylvania
Registered: Jun 99


 - posted 08-08-2001 06:36 AM      Profile for Randy Stankey   Email Randy Stankey   Send New Private Message       Edit/Delete Post 
Aah! 139 meg over a modem?! That's the reason I haven't seen it!

 |  IP: Logged

John Pytlak
Film God

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


 - posted 08-08-2001 07:34 AM      Profile for John Pytlak   Author's Homepage   Email John Pytlak   Send New Private Message       Edit/Delete Post 
Mark said: "I have always wondered where one can get those back articles that appeared in the old SMPTE journals"

John Walsh is correct that the SMPTE is in the process of putting articles on their website. For now, they have put indices and more recent articles and presentations "on-line". You can join the SMPTE and subscribe to their library service at:
http://www.smpte.org/membership/

The SMPTE "members only" library is at:
http://www.smpte.org/members_only/

You can work with your local library to get copies of articles published in the SMPTE Journal. Libraries that subscribe to the SMPTE Journal would include film schools (e.g., UCLA, USC) and science/engineering schools that teach film or television technology (e.g., Rochester Institute of Technology).


------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

 |  IP: Logged

Dave Macaulay
Film God

Posts: 2080
From: Toronto, Canada
Registered: Apr 2001


 - posted 08-10-2001 04:19 PM      Profile for Dave Macaulay   Email Dave Macaulay   Send New Private Message       Edit/Delete Post 
Adam:
Agreed, facts are confused, this article sounds like the crap spouted by marketing people.

- Only a few very old water cooled Imax/Omnimax systems use 12kW lamps. Since around 1985 or so all have been 15kW. There are a fair number of 4 and 4.5 kW air cooled ones as well, and one or two 7kw (maybe, if they are still running and have never upped to 15kW) aircooled "classic" machines.
There are 2 Imax "Solido" 3-D single case 2-strip cameras with a fixed interocular, dictated by the lens diameters when it was designed. With 1000ft magazines it's probably in the 240 pound range. There can also be a 3D rig with 2 "standard" MK1 Imax cameras at 90 degrees with a 45 degree mirror. This thing weighs a bit more, and has a gyro stabilized mount available that probably weighs as much again. The first 3D Imax film, made for Expo86 in Vancouver, used this one. Imax doesn't seem to want to admit to this movie, it isn't on their film list and I can't even remember the name. Transitions? It had the teddy bear scene, and the robot arm breaking an egg in your lap. The twin rig was used on The Last Buffalo and also Imagine - if that's the one with the little people - as the freedom to mess with interocular was needed for that effect. There was also a 3D rig with the cameras about 6 feet apart for some weird forced shots.
There are many problems with the mirror rig - it takes a LONG time to set up using reticles projected from the cameras onto a screen for alignment. This needs a large dark area, obviously... Plus, the amount of cabling and electronics is a nightmare.

- The author talks about 48fps as if it's a standard feature. Not. There are almost zero 48fps films and only a few more projectors that can show 48. Ontario Place and Hull are the only ones I'm sure of. The cameras get very snarky if expected to run at 48 for long (it's about the limit for the standard camera) and the projectors like it even less. The film is moving twice as fast, and has to be stopped and accelerated again every frame. The inertial energy is proportional to the square of the velocity...

- 20 minutes to reload? Nonsense. The 3D one maybe, but a decent camera operator can do a 2D mag change in about 5 minutes maximum - with a good cleaning thrown in. We can't count the time to reload the mag, an assistant does that in a dark bag during shooting.

- 3 minute rolls? OK, but there are also 2000' (6 minutes...) magazines and Kodak did supply 2000 foot 65mm neg rolls. These were made for the Stones movie, to cut by half the mag changes. Filming theirive show apparently made the effort worthwhile. There are also 300' mags for shots where weight or size is a problem, they were used in the infamous Catch the Sun skydiving shoot that may have financially saved Imax in the early days.

- There are lots more than 2 cameras of course. Camera #2 was the one used trying to parachute but there were about 8 working ones the last time I looked. 2 of these were reserved for only spaceflight though.

- There are at least 2 very different generations of 2D Imax camera, the solido Imax3D ones, plus as the competition's 15/70 models) which we shouldn't call Imax of course).

Plus, it didn't even really tell us how it works!

I have a bunch of photos somewhere, if I get ambitious I will try to find one that shows the front end of a projector. If anyone (Gord?) can scan a threading diagram from a manual that would be excellent!


 |  IP: Logged



All times are Central (GMT -6:00)
This topic comprises 6 pages: 1  2  3  4  5  6 
 
Post New Topic  Post A Reply Close Topic    Move Topic    Delete Topic    next oldest topic   next newest topic
 - Printer-friendly view of this topic
Hop To:



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.

© 1999-2018 Film-Tech Cinema Systems, LLC. All rights reserved.