Film-Tech Forum ARCHIVE: Mag Oxide

This is topic Mag Oxide in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Gordon McLeod (Member # 33) on 08-02-2001, 01:20 PM:

Was Chromium Dioxide or Cobalt doped oxides ever used on either mag fullcoat or striped release print?
THe improved noise and high frequency response should have been a noticable improvement over the standard red oxide
What was the black oxide tape?

Posted by John Pytlak (Member # 331) on 08-02-2001, 01:49 PM:

Found this interview with Thomlinson Holman, which hints at a significant formulation change:
http://www.mel-lambert.com/Writer/Interviews/MIX.Tom_Holman.html

"Did you continue to work with Dolby on the evolution of its 4-track 35 mm systems and 6-track, 70 mm formats?
To a certain extent. What we did on "Return of the Jedi" was change the magnetic oxide. When we looked at the magnetic oxide they were striping on 70 mm prints in
1983, it was equivalent to Scotch 102 from the early Fifties! The problem was there was only one vendor, but a second vendor was interested and had bought up the old
MGM striping plant. We went with them because they were striping a much better oxide. The interesting thing was that the difference you got in headroom was 11 or 12 dB
-- a major improvement.

"Jedi" was pretty good sounding on 70 mm, but there were still a few orchestral passages where you could hear IM. What was happening was that the accumulated
distortion over all those [dubbing] generations had suddenly become audible; it wasn't audible on the [print] master but became obvious on the releases print -- it was just
one generation too many. By the next year we pushed 3M into making much better mag-film stock for the post-production generations. When we had got to "Indiana Jones
and the Temple of Doom," where was an incredible passage for IM where the bass drum is banging with choral music above it -- the [new formulation] passed the test, and
it did not intermodulate audibly."

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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

Posted by Gordon McLeod (Member # 33) on 08-02-2001, 06:35 PM:

Interesting article and interesting the note that in 1980 Lucas object was all digital movie making

Posted by Steve Guttag (Member # 268) on 08-03-2001, 06:32 AM:

Other things changed in 1983 too...The 70mm track widths (how wide the head gaps are, not the actual striping) got wider and the reference level went up too. That is, we had a true 185nWb/m reference level. In recent tests I performed...the new reference level amounted to about 7.5dB in increased level on the film for Dolby Level. 1983 (Jedi) was a pivotal year for 70mm magnetic. I believe the 35mm magnetic levels and track widths changed as well.

The original striping facility was Magnacraft. I believe CFI is the new facility Tom spoke of.

Steve

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"Old projectionists never die, they just changeover!"

Posted by Gordon McLeod (Member # 33) on 08-03-2001, 08:52 AM:

Apparently there is also a company in CA called America Film and Tape that does stripping

Posted by John Pytlak (Member # 331) on 08-03-2001, 09:22 AM:

Link: http://americanfilmtape.visualnet.com/