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  1. #31
    Sparky's Avatar
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    Here's the deal (better than anything I can possibly speculate on):

    "Whilst the camera was relatively straight forward to design, considerable problems were experienced with the projector. At 24 f.p.s. 337.5' of film would pass through the projector every minute, against 90' for standard 35mm. This was not a problem in the camera, where exposure times could be kept short and the film moved evenly by a claw. In the projector, however, the film had to be kept stationary much longer whilst each frame was projected onto the screen. This rendered conventional Maltese cross intermittent movements unusable - the inertia involved with the fast-moving film causing excessive loading on the perforations and damage to the film."


    - http://www.70mm.org.uk/imax.htm


    So - I guess it IS just a projector issue and NOT the camera.

  2. #32

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    So the bottom line is that 65/70mm film for motion picture use is perforated, regardless of the method of projection. Therefore the manufacturers who make this stock (Kodak) have the equipment to perforate.

  3. #33
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    Well - the bottom line REALLY would be that the 70mm film sold by kodak would be useable in a hassy, let's say... even if the 'image area' (wonder how the heck that's defined) is only 65mm or whatever (if I'm reading you correctly)...

    unless, of course, that's the difference between type I and type II perforations.

  4. #34
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    Quote Originally Posted by PHOTOTONE View Post
    IMAX camera film is perforated, as well as the print that is projected. While it is true that the projector uses a "rolling loop" for the frame-by-frame pull down at the projection aperture, there still needs to be a way to register the film, as well as a way to pull the film through the rest of the mechanism, and peforations are essential for this.

    It is my understanding in regards 70mm cine film, that the ONLY difference in size between the camera stock and the release prints is that originally, the release prints were 5mm wider (to make 70mm) on the OUTSIDE of the perforations to allow for the magnetic sound tracks applied to the film stock on the outside edges of the film, outside the perforations. Thus the perforations were identical between camera stock and release print.
    Of course IMAX does not use sound tracks applied to the film, rather the sound tracks are on a separate film run in sync with the picture.
    Current 35mm release prints have opticaly embedded in the emulsion up to 4 different sound systems all at the same time.

    Firstly the standard optical analogue stereo sound, between the perfs and image area on the one side. Second DTS digital between the perfs and the image area on the other side. Third Dolby digital, between each perf. And lastly SDDS in the area outside the perfs on either side.

    The DTS, Dolby, SDDS are there to sync the projector with CD rom for the sound, or some other device.

    I would guess a current 70mm release print would have a similar set up.

  5. #35
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    Hi Guys,

    My four Hasselblad A70 backs all take the TYPE II perforated film. I've been stocking up on this stuff for years, I have about twenty 100' cans in my freezer, many different types of B&W and color emulsions, including some exotic aerial emulsions. All go through the A70 backs just fine. Also, I have three "rubber wheels" I got from a guy in Massachusetts years ago on ebay, that interchanged with the Hasselblad "wheeled cog" that pulls the perforated film through. Interchanging the regular wheel, for the rubber wheel, allows me to run unperforated 70mm film through any of my A70 backs. It has proved to be reliable for me, over time.

    Fifteen foot rolls of B&W 70mm film, I develop in my Kindermann 70mm daylight developing tank. This is a gigantic plastic daylight tank, which uses a large steel reel. And I have the 70mm Kindermann loading stand, which holds the steel reel, and a 70mm cartridge, with a nice hand-crank. I also have a generic "medical x-ray" 70mm reel, made of plastic, which holds about 12' of 70mm film. After washing the developed film, I cut the long roll into 3' strips, to hang and dry. I then cut the 3' strips into strips of four, and place them into 70mm Vue-All negative pages.

    Everything works beautifully, with no bugs.
    Last edited by Nokton48; 10-28-2007 at 10:23 AM. Click to view previous post history.

  6. #36
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    Quote Originally Posted by Matt5791 View Post
    I would guess a current 70mm release print would have a similar set up.
    So - what you're saying is that it would work JUST FINE for film cameras? (assuming the optical strips are accomodated by the same emulsion as the 'image area' and therefore are 'set up' by the cine-camera...?

  7. #37

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    Quote Originally Posted by Matt5791 View Post
    Current 35mm release prints have opticaly embedded in the emulsion up to 4 different sound systems all at the same time.

    Firstly the standard optical analogue stereo sound, between the perfs and image area on the one side. Second DTS digital between the perfs and the image area on the other side. Third Dolby digital, between each perf. And lastly SDDS in the area outside the perfs on either side.

    The DTS, Dolby, SDDS are there to sync the projector with CD rom for the sound, or some other device.

    I would guess a current 70mm release print would have a similar set up.
    70mm release prints (of any former,or current format) have never had an optical sound track, ever. The whole purpose of 70mm release prints, even though the camera stock is 65mm wide, was to allow for the application of magnetic stripes on which the sound tracks were dubbed. Now, I am sure, for the Super Formats such as Imax, Iwerks, etc.,, there is just an optical time-code to sync with separate CD or DVD based sound.

    The perforations are identical in spacing in the camera stock and release prints. It is only the little tiny bit of extra film stock on the outside of the perforations that is different. I don't know, but I wouldn't be surprised if what is actually marketed as 70mm perforated still-camera film, is not actually 65mm wide, because, in still cameras, the area on the outside of the perforations could not be used for imaging, obviously.

    Another reason for having perforations on 70mm release prints, even for Imax, is that all the release prints have to be wet gate contact printed from the camera negatives in a contact printing machine that relies on the perforations to keep everything lined up and registered.

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