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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 |
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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 |
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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
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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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