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Variable Density Greyscale Film for audio



 
 
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  #1  
Old September 21st 06, 04:27 AM posted to rec.photo.film+labs,rec.arts.movies.tech,alt.photography,alt.photography.schools.nyip,rec.photo.darkroom
Radium
external usenet poster
 
Posts: 25
Default Variable Density Greyscale Film for audio

Hi:

I like using variable-density analog B&W negative film optical tracks
for audio. The audio characteristics of the film make my mouth-water.
Yes, for some wierd reason, the film's audio makes me hungry.

Audio signal, in the form of light changing its intensity in a
analogous manner to the sound, is shined onto a negative film. The film
is developed and playback is accomplished by shining light of a
constant intensity onto the developed film. As the light goes through
the film, the patterns on the film will change the intensity of the
light that is received by a photoelectric cell. The change in light
intensity results in a changing electric current which is sent into an
amplifier and then to a loudspeaker.

http://www.mtsu.edu/~smpte/twenties.html

"The Tri Ergon Process uses a technology known as variable density,
which differed from a later process known as variable area. The Tri
Ergon process had a pattented flywheel mechanism on a sprocket which
prevented variations in film speed. This flywheel helped prevent
distortion of the audio. Tri Ergon relied on the use of a
photo-electric cell to transduce mechanicalsound vibrations into
electrical waveforms and then convert the electrical waveforms into
light waves. These light waves could then be optically recorded onto
the edge of the film through a photographic process. Another
photo-electric cell could then be used to tranduce the waveform on the
film into an electrical waveform during projection. This waveform
could then be amplified and played to the audience in the Theater. The
Fox Film Corporation acquired the rights to the Tri Ergon technology in
1927. "

The ERPI system, Fox-Case's Movietone, and De Forest's Phonofilm use
variable-density recording film audio



Regards,

Radium

  #2  
Old September 23rd 06, 10:25 PM posted to rec.photo.darkroom
Richard Knoppow
external usenet poster
 
Posts: 751
Default Variable Density Greyscale Film for audio


"Radium" wrote in message
oups.com...
Hi:

I like using variable-density analog B&W negative film
optical tracks
for audio. The audio characteristics of the film make my
mouth-water.
Yes, for some wierd reason, the film's audio makes me
hungry.

Audio signal, in the form of light changing its intensity
in a
analogous manner to the sound, is shined onto a negative
film. The film
is developed and playback is accomplished by shining light
of a
constant intensity onto the developed film. As the light
goes through
the film, the patterns on the film will change the
intensity of the
light that is received by a photoelectric cell. The change
in light
intensity results in a changing electric current which is
sent into an
amplifier and then to a loudspeaker.

http://www.mtsu.edu/~smpte/twenties.html

"The Tri Ergon Process uses a technology known as variable
density,
which differed from a later process known as variable
area. The Tri
Ergon process had a pattented flywheel mechanism on a
sprocket which
prevented variations in film speed. This flywheel helped
prevent
distortion of the audio. Tri Ergon relied on the use of a
photo-electric cell to transduce mechanicalsound
vibrations into
electrical waveforms and then convert the electrical
waveforms into
light waves. These light waves could then be optically
recorded onto
the edge of the film through a photographic process.
Another
photo-electric cell could then be used to tranduce the
waveform on the
film into an electrical waveform during projection. This
waveform
could then be amplified and played to the audience in the
Theater. The
Fox Film Corporation acquired the rights to the Tri Ergon
technology in
1927. "

The ERPI system, Fox-Case's Movietone, and De Forest's
Phonofilm use
variable-density recording film audio



Regards,

Radium

If you are really interested in this there is a perfectly
enormous amount of material in the _Journal of the Society
of Motion Picture Engineers_, later the _Journal of Motion
Picture and Television Engineers_. Variable density
recording was very widely used for Hollywood motion pictures
from the beginning of sound until it was eventually
supplanted by variable area (more accurately variable width)
tracks around the 1960's.
Because they owned nearly all of the patents covering
electronic amplifiction and vacuum tubes Western Electric
and RCA were able to suppress competitors in recording
apparatus so that by about 1930 Fox-Case Movietone and other
systems dissapeared. The last sound-on-disk was released
about 1933 but had been pretty much replaced by sound on
film. Both Fox and Warner Brothers became Western Electric
licensees, Warner later changed to RCA who had a more
sensible royalty charge.
Until the late 1930's Western Electric made variable
density recorders and RCA always made variable area. Both
companies found methods to use their modulators to produce
both kinds of tracks. I've heard intermixed tracks of both
kinds made by Western Electric recorders and have been
unable to tell them apart.
Good photographic recording is excellent but one has a
hard time finding examples of older tracks these days
because so many original release prints are no longer in
projectable (or playable) condition and later reprints,
restorations, etc., are not printed correctly so the sound
can be quite distorted.
From about 1940 both 20th Century-Fox and M-G-M were
using double width, push-pull density tracks for original
recording. This equipment was made by Western Electric and
was flat from 40 to 10,000 hz, had under 1% distortion, and
about a 70db signal to noise ratio. Release tracks were
never this good but the best of them are quite impressive.
Photographically, sound recording has many special
problems not encountered in pictorial photography. For one
thing it is necessary to compensate for image spread in
printing, especially in width recording. A good method of
determining the correct recorder and printer exposures was
not developed until the late 1930's. There is also the
problem of reciprocity failure in density recording using
the ribbon light valve (Western Electric) because of the
very short exposure times at high frequencies.
Once magnetic recording was sufficiently perfected all
studios switched to it for original recording. Not much
photographic recording for other than release prints was
done after about 1951.
At any rate, we are right back to sound-on-disk again
albeit digital disks.
The original message was sent to several news groups, I
am confining my reply to rec.photo.darkroom. This does have
some on topic content because good photographic sound
recording is vitally dependant on proper printing and
processing.


--
---
Richard Knoppow
Los Angeles, CA, USA






  #3  
Old September 25th 06, 01:04 AM posted to rec.photo.darkroom
Radium
external usenet poster
 
Posts: 25
Default Variable Density Greyscale Film for audio


Richard Knoppow wrote:

From about 1940 both 20th Century-Fox and M-G-M were
using double width, push-pull density tracks for original
recording. This equipment was made by Western Electric and
was flat from 40 to 10,000 hz, had under 1% distortion, and
about a 70db signal to noise ratio. Release tracks were
never this good but the best of them are quite impressive.


Are these variable-density or variable-area?

  #4  
Old September 26th 06, 12:03 AM posted to rec.photo.darkroom
Richard Knoppow
external usenet poster
 
Posts: 751
Default Variable Density Greyscale Film for audio


"Radium" wrote in message
ups.com...

Richard Knoppow wrote:

From about 1940 both 20th Century-Fox and M-G-M were
using double width, push-pull density tracks for original
recording. This equipment was made by Western Electric
and
was flat from 40 to 10,000 hz, had under 1% distortion,
and
about a 70db signal to noise ratio. Release tracks were
never this good but the best of them are quite
impressive.


Are these variable-density or variable-area?


Variable density. M-G-M used variable density
exclusively, Fox used both. I don't know if Fox used any
area tracks for original recording. Warner Brothers and some
others used push-pull Class-A variable area tracks for some
original recording. Republic Pictures used Class-B double
width variable area, AFAIK, that was unique. The late Waddy
Watson, who became head of Universal's sound department
worked for Republic in the old days and told me that they
sometimes spent all night lining up the recording system. In
theory Class-B push pull has virtually no background noise
but the ballance has to be perfect or the distortion becomes
serious and is of a very annoying kind. I have also seen
samples of push-pull tracks from Paramount but I am not sure
how widely they were used there. Paramount was one of the
first studios to switch to magnetic recording for original
recording purposes thanks to Loren Ryder. I think they
changed over about 1951 but were making some magnetic tracks
as early as 1948 on home made equipment. John Aalberg, who
was once head of RKO-Radio sound told me that they had
experimented with push-pull but could not hear enough
difference to use it routinely. BTW, don't judge RKO sound
quality by the television reprints, the sound is not printed
correctly and results in a very spitty donald duck quality.
Some current Turner Classic Movies prints are very good
however.
IMO Fox and M-G-M were right at the top for both quality
of sound and skill in re-recording although all the majors
did very good work.
The M-G-M recording system is described in detail in the
Journal of the Motion Picture Engineers for sometime in 1938
or 1939, I don't have the citation at hand but I think the
article was written by John K. Hillyard.
For much more on various film recording systems, in
cluding the three chanel stereo system used by Bell Labs,
see: _Elements of Sound Recording_ John G. Frayne and Halley
Wolfe, 1949, John Wiley and Sons, Inc. See also: _Motion
Picture Sound Engineering_ Various authors, New York, 1938,
D. Van Nostrand Co.
Both are a bit rare but larger libraries should be able
to get them. Dr. John Frayne was a poineer in sound
recording who worked for Bell Labs and was materially
responsible for the development of the modern stereo disc
cutter. The second book was developed from a course in
motion picture sound recording given by the Research Council
of the Academy of Motion Picture Arts and Sciences. While
both are very old much of the information is still valid and
they do describe the equipment in use from about the mid
1930's to the 1950's.
This has been long an area of special intrest to me so
your original post, although off topic, pricked up my
attention.


--
---
Richard Knoppow
Los Angeles, CA, USA




 




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