What wavelengths of light specifically affect the type of film used in the first movie containing an variable-density optical audio track? I am specifically interested in the chemical composition of the optical audio track.
From what I know, most of the more modern films are unaffected by red light.
I'm thinking of a theoretical device using analog audio recording on VD optical tracks containing the oldest film chemical composition. The source of light are multiple laser beams consisting of wavelengths that could record the audio onto the film. Each beam has a different wavelength. The beams are then mixed together to get a single beam of all the necessary wavelengths. The beam then shines onto the film to record the audio.
I don't have much of an application here. I'm just in it for the science.
> What wavelengths of light specifically affect the type of film used in > the first movie containing an variable-density optical audio track? I > am specifically interested in the chemical composition of the optical > audio track.
> From what I know, most of the more modern films are unaffected by red > light.
> I'm thinking of a theoretical device using analog audio recording on > VD optical tracks containing the oldest film chemical composition. The > source of light are multiple laser beams consisting of wavelengths > that could record the audio onto the film. Each beam has a different > wavelength. The beams are then mixed together to get a single beam of > all the necessary wavelengths. The beam then shines onto the film to > record the audio.
> I don't have much of an application here. I'm just in it for the > science.
> Thanks
I have not idea, but Kodak has a museum in Rochester (NY). Call them, they might be able to help.
> What wavelengths of light specifically affect the type of film used in > the first movie containing an variable-density optical audio track? I > am specifically interested in the chemical composition of the optical > audio track.
> From what I know, most of the more modern films are unaffected by red > light.
> I'm thinking of a theoretical device using analog audio recording on > VD optical tracks containing the oldest film chemical composition. The > source of light are multiple laser beams consisting of wavelengths > that could record the audio onto the film. Each beam has a different > wavelength. The beams are then mixed together to get a single beam of > all the necessary wavelengths. The beam then shines onto the film to > record the audio.
> I don't have much of an application here. I'm just in it for the > science.
> Thanks
Are you sure you aen't related to Hughes/Eugene? -- Regards, Savageduck
> What wavelengths of light specifically affect the type of > film used in > the first movie containing an variable-density optical > audio track? I > am specifically interested in the chemical composition of > the optical > audio track.
> From what I know, most of the more modern films are > unaffected by red > light.
> I'm thinking of a theoretical device using analog audio > recording on > VD optical tracks containing the oldest film chemical > composition. The > source of light are multiple laser beams consisting of > wavelengths > that could record the audio onto the film. Each beam has a > different > wavelength. The beams are then mixed together to get a > single beam of > all the necessary wavelengths. The beam then shines onto > the film to > record the audio.
> I don't have much of an application here. I'm just in it > for the > science.
> Thanks
Nearly all films used for making photographic sound negatives were blue sensitive (i.e., color blind). The main difference between film for variable density and variable width (AKA variable area) was the contrast. Variable density recording requires low to medium contrast film and variable width requires quite high contrast. The exact contrast is determined by the film used for making the prints. That is tests are made to find the best combination of exposure and development of the sound negative to minimize distortion in the final print. The contrast of the print when composite prints are made (both picture and sound) is determined by the picture so the print contrast is usually fixed and requires the negative to match it. One of the problems with both types of recording, but especially for variable width recording, is image spread in the emulsion. This is also called irradiation and is a blurring of the image due to diffusion of light by the emulsion. Modern films, which have much thinner emulsions than those of perhaps fifty years ago, do not suffer as much from irradiation but still have some. The idea of matching the negative to the positive is partially to counteract the image spread since the spread in the positive will correct for that in the positive if exactly right. Other methods were tried in the old days. For instance, the use of ultra-violet lamps in the recorder were common in the mid to late 1930s. This system does result in sharper images since it confines exposure to the surface of the emulsion, but the intensity of the lamps is marginal so getting properly exposed negatives was difficult. Also tried was using film with a yellow dye in the emulsion. This also confined the exposure to the surface but had the same problems with lack of enough light. There are modern systems of photographic recording that use beams of multiple colored lights as you suggest for stereo. For the most part photographic recording is a thing of the past. Magnetic recording replaced photographic recording for original tracks beginning around 1948 and had completely supplanted it by the mid 1950s. Photographic tracks for release prints continues to some extent to the present. They are economical to make and have long life. However, for most theatrical release the sound is now on a digital disc, so we have come full circle to the sound-on-disc method use for the first commercial sound pictures. An excellent source for material on motion picture sound is the archives of the _Journal of the Society of Motion Picture and Television Engineers_ Larger library systems probably have it. I don't know if the complete journals are available on disc or on line. Nearly all developments in motion picture sound recording and related topics such as the improvement in film made for sound recording is to be found in this journal. As far as modern film, nearly all B&W film made now is "panchromatic", that is sensitive to all visible colors. Simple emulsions are sensitive only to blue and near ultra-violet. By adding sensitizing dyes to the emulsion the color sensitivity can be extended toward red. "Orthochromatic" film is sensitive to blue, green, and some yellow. Ortho film became available about the mid 'teens. Panchromatic film became available about the early 1920's but was not adopted by the motion picture industry until the introduction of sound. Because the arc lighting equipment common in motion picture production was mechanically noisy sound recording precluded its use. The output of blue light from incandescent lamps is much smaller than from arc lamps so the orthochromatic film of the time was simply not sensitive enough and a switch to panchromatic film had to be made. This, in turn, required a change in the way sets were painted, in makeup, in lighting, etc. However, the film used in film recording machines was typically the same film used for duplicating negatives (variable density) or for release printing (for variable width)continued to be blue sensitive only. These films continued to be used until specially made sound recording films became available in about the mid 1930s. -- Richard Knoppow Los Angeles, CA, USA dickb...@ix.netcom.com
GreenXenon wrote: > What wavelengths of light specifically affect the type of film used in > the first movie containing an variable-density optical audio track? I > am specifically interested in the chemical composition of the optical > audio track.
The first variable-density tracks were in the 1910s (such as Tigerstedt and Tri-Ergon) so probably used orthochromatic film, sensitive to blue and green.
> From what I know, most of the more modern films are unaffected by red > light.
Just backward: the older films were not sensitive to red light. Panchromatic film, which is sensitive to red, became common in cinematography in the 1920s.
Of course in the standard studio equipment of early talkies, the soundtrack recording was done on a different strip of film in a different machine from the camera, so the color response of the film in the audio recording machine didn't matter. You could even use pre-orthochromatic film, which was sensitive mostly to blue wavelengths, as long as your flickering light source had enough output in the blue to properly expose the track.
Only in a portable camera which exposed both picture and sound on the same negative would color sensitivity be an issue, and as far as I know the cameras that did (RCA 16mm models from the mid-1930s are the first I know of) used variable-area recording rather than variable-density.
> I'm thinking of a theoretical device using analog audio recording on > VD optical tracks containing the oldest film chemical composition. The > source of light are multiple laser beams consisting of wavelengths > that could record the audio onto the film. Each beam has a different > wavelength. The beams are then mixed together to get a single beam of > all the necessary wavelengths. The beam then shines onto the film to > record the audio.
This is unnecessarily complicated. The film is black-and-white. As long as the optical track gets enough light to expose it properly, of a color to which it is sensitive, it doesn't care if the light is a mix of wavelengths or just one wavelength. So with orthochromatic film you could use a blue or green laser by itself, rather than worrying about multiple sources and mixing beams.
In fact, there is an advantage to using a single wavelength, in that you can use a simpler lens to focus the optical track without having to correct for chromatic aberration.
On May 12, 11:29 am, Neil Midkiff <nmidk...@earthlink.net> wrote:
> GreenXenon wrote: > > I'm thinking of a theoretical device using analog audio recording on > > VD optical tracks containing the oldest film chemical composition. The > > source of light are multiple laser beams consisting of wavelengths > > that could record the audio onto the film. Each beam has a different > > wavelength. The beams are then mixed together to get a single beam of > > all the necessary wavelengths. The beam then shines onto the film to > > record the audio.
> This is unnecessarily complicated. The film is black-and-white. As > long as the optical track gets enough light to expose it properly, of a > color to which it is sensitive, it doesn't care if the light is a mix of > wavelengths or just one wavelength. So with orthochromatic film you > could use a blue or green laser by itself, rather than worrying about > multiple sources and mixing beams.
Blue takes up less space than green [for the same amount of data], so I'm guessing blue would make more efficient use of the film's length. This is because blue light is of shorter wavelength than green light. Per area, blue can represent more info than green.
> Blue takes up less space than green [for the same amount of data], so > I'm guessing blue would make more efficient use of the film's length. > This is because blue light is of shorter wavelength than green light. > Per area, blue can represent more info than green.
> What is the best wavelength of blue to use?
Aren't the things you're comparing here (the wavelength of light and the density of audio "data" on film at ordinary projection speed) many orders of magnitude different? Sounds like a silly distinction between colors.
-- Found--the gene that causes belief in genetic determinism
>>> I'm thinking of a theoretical device using analog audio recording on >>> VD optical tracks containing the oldest film chemical composition. > Blue takes up less space than green [for the same amount of data], so > I'm guessing blue would make more efficient use of the film's length. > This is because blue light is of shorter wavelength than green light. > Per area, blue can represent more info than green.
> What is the best wavelength of blue to use?
You're confusing two different sorts of recording here. It's true that in digital recording to optical discs the shorter wavelength of blue light is an advantage (as in Blu-Ray vs. standard DVD), because that style of recording looks at the presence or absence of individual "pits" representing binary data, and blue light can be focused more tightly onto smaller pits on the disc.
This has almost nothing to do with variable-density audio recording on film, in which analog audio signals are photographed as varying gray tones on the track.
Black-and-white film is inherently grainy; the various levels of gray in a VD track are made up of varying densities of exposed-and-developed grains -- starting out as crystals of a silver halide, then developed to bits of metallic silver in the emulsion. On a microscopic scale, b/w film is just that: opaque silver bits in a clear emulsion. It only looks gray on a broader view, just as a halftoned newspaper photograph made up of dots of black ink on paper simulates grayscales at ordinary reading distance.
So it's necessary for the soundtrack to be wide enough (usually at least a couple of millimeters) that the reading process "looks at" a broad enough area to average out the film grain. If you used a laser spot pickup similar to the one in a DVD player to read a VD film soundtrack, the output would be full of random noise as the individual grains passed by the reader.
And of course, to expose this wide a track, the sound recorder must project the flickering light through a slit that's as wide as the track.
In other words, the area you're looking at is so much larger than the wavelength of light that the color of the light for recording or playback doesn't matter.
> On May 12, 11:29 am, Neil Midkiff <nmidk...@earthlink.net> > wrote:
>> GreenXenon wrote:
>> > I'm thinking of a theoretical device using analog audio >> > recording on >> > VD optical tracks containing the oldest film chemical >> > composition. The >> > source of light are multiple laser beams consisting of >> > wavelengths >> > that could record the audio onto the film. Each beam >> > has a different >> > wavelength. The beams are then mixed together to get a >> > single beam of >> > all the necessary wavelengths. The beam then shines >> > onto the film to >> > record the audio.
>> This is unnecessarily complicated. The film is >> black-and-white. As >> long as the optical track gets enough light to expose it >> properly, of a >> color to which it is sensitive, it doesn't care if the >> light is a mix of >> wavelengths or just one wavelength. So with >> orthochromatic film you >> could use a blue or green laser by itself, rather than >> worrying about >> multiple sources and mixing beams.
> Blue takes up less space than green [for the same amount > of data], so > I'm guessing blue would make more efficient use of the > film's length. > This is because blue light is of shorter wavelength than > green light. > Per area, blue can represent more info than green.
> What is the best wavelength of blue to use?
I'm not sure where you got this idea. For sound recording using conventional analogue methods the wavelength of the light is so much smaller than the data to be recorded that the wavelength does not matter. I wonder if we are talking about the same things here.
-- -- Richard Knoppow Los Angeles, CA, USA dickb...@ix.netcom.com
> >>> I'm thinking of a theoretical device using analog audio recording on > >>> VD optical tracks containing the oldest film chemical composition. > > Blue takes up less space than green [for the same amount of data], so > > I'm guessing blue would make more efficient use of the film's length. > > This is because blue light is of shorter wavelength than green light. > > Per area, blue can represent more info than green.
> > What is the best wavelength of blue to use?
> You're confusing two different sorts of recording here. It's true that > in digital recording to optical discs the shorter wavelength of blue > light is an advantage (as in Blu-Ray vs. standard DVD), because that > style of recording looks at the presence or absence of individual "pits" > representing binary data, and blue light can be focused more tightly > onto smaller pits on the disc.
> This has almost nothing to do with variable-density audio recording on > film, in which analog audio signals are photographed as varying gray > tones on the track.
> Black-and-white film is inherently grainy; the various levels of gray in > a VD track are made up of varying densities of exposed-and-developed > grains -- starting out as crystals of a silver halide, then developed to > bits of metallic silver in the emulsion. On a microscopic scale, b/w > film is just that: opaque silver bits in a clear emulsion. It only > looks gray on a broader view, just as a halftoned newspaper photograph > made up of dots of black ink on paper simulates grayscales at ordinary > reading distance.
> So it's necessary for the soundtrack to be wide enough (usually at least > a couple of millimeters) that the reading process "looks at" a broad > enough area to average out the film grain. If you used a laser spot > pickup similar to the one in a DVD player to read a VD film soundtrack, > the output would be full of random noise as the individual grains passed > by the reader.
> And of course, to expose this wide a track, the sound recorder must > project the flickering light through a slit that's as wide as the track.
> In other words, the area you're looking at is so much larger than the > wavelength of light that the color of the light for recording or > playback doesn't matter.
> -Neil Midkiff
What determines the highest-frequency sound that can be recorded onto a VD optical track?
> On May 12, 1:23 pm, Neil Midkiff <nmidk...@earthlink.net> wrote:
> > GreenXenon wrote: > > >> GreenXenon wrote:
> > >>> I'm thinking of a theoretical device using analog audio recording on > > >>> VD optical tracks containing the oldest film chemical composition. > > > Blue takes up less space than green [for the same amount of data], so > > > I'm guessing blue would make more efficient use of the film's length. > > > This is because blue light is of shorter wavelength than green light. > > > Per area, blue can represent more info than green.
> > > What is the best wavelength of blue to use?
> > You're confusing two different sorts of recording here. It's true that > > in digital recording to optical discs the shorter wavelength of blue > > light is an advantage (as in Blu-Ray vs. standard DVD), because that > > style of recording looks at the presence or absence of individual "pits" > > representing binary data, and blue light can be focused more tightly > > onto smaller pits on the disc.
> > This has almost nothing to do with variable-density audio recording on > > film, in which analog audio signals are photographed as varying gray > > tones on the track.
> > Black-and-white film is inherently grainy; the various levels of gray in > > a VD track are made up of varying densities of exposed-and-developed > > grains -- starting out as crystals of a silver halide, then developed to > > bits of metallic silver in the emulsion. On a microscopic scale, b/w > > film is just that: opaque silver bits in a clear emulsion. It only > > looks gray on a broader view, just as a halftoned newspaper photograph > > made up of dots of black ink on paper simulates grayscales at ordinary > > reading distance.
> > So it's necessary for the soundtrack to be wide enough (usually at least > > a couple of millimeters) that the reading process "looks at" a broad > > enough area to average out the film grain. If you used a laser spot > > pickup similar to the one in a DVD player to read a VD film soundtrack, > > the output would be full of random noise as the individual grains passed > > by the reader.
> > And of course, to expose this wide a track, the sound recorder must > > project the flickering light through a slit that's as wide as the track.
> > In other words, the area you're looking at is so much larger than the > > wavelength of light that the color of the light for recording or > > playback doesn't matter.
> > -Neil Midkiff
> What determines the highest-frequency sound that can be recorded onto > a VD optical track?- Hide quoted text -
> On May 12, 1:23 pm, Neil Midkiff <nmidk...@earthlink.net> wrote:
> > GreenXenon wrote: > > >> GreenXenon wrote:
> > >>> I'm thinking of a theoretical device using analog audio recording on > > >>> VD optical tracks containing the oldest film chemical composition. > > > Blue takes up less space than green [for the same amount of data], so > > > I'm guessing blue would make more efficient use of the film's length. > > > This is because blue light is of shorter wavelength than green light. > > > Per area, blue can represent more info than green.
> > > What is the best wavelength of blue to use?
> > You're confusing two different sorts of recording here. It's true that > > in digital recording to optical discs the shorter wavelength of blue > > light is an advantage (as in Blu-Ray vs. standard DVD), because that > > style of recording looks at the presence or absence of individual "pits" > > representing binary data, and blue light can be focused more tightly > > onto smaller pits on the disc.
> > This has almost nothing to do with variable-density audio recording on > > film, in which analog audio signals are photographed as varying gray > > tones on the track.
> > Black-and-white film is inherently grainy; the various levels of gray in > > a VD track are made up of varying densities of exposed-and-developed > > grains -- starting out as crystals of a silver halide, then developed to > > bits of metallic silver in the emulsion. On a microscopic scale, b/w > > film is just that: opaque silver bits in a clear emulsion. It only > > looks gray on a broader view, just as a halftoned newspaper photograph > > made up of dots of black ink on paper simulates grayscales at ordinary > > reading distance.
> > So it's necessary for the soundtrack to be wide enough (usually at least > > a couple of millimeters) that the reading process "looks at" a broad > > enough area to average out the film grain. If you used a laser spot > > pickup similar to the one in a DVD player to read a VD film soundtrack, > > the output would be full of random noise as the individual grains passed > > by the reader.
> > And of course, to expose this wide a track, the sound recorder must > > project the flickering light through a slit that's as wide as the track.
> > In other words, the area you're looking at is so much larger than the > > wavelength of light that the color of the light for recording or > > playback doesn't matter.
> > -Neil Midkiff
> What determines the highest-frequency sound that can be recorded onto > a VD optical track?- Hide quoted text -
> - Show quoted text -
The speed at which the film moves, the bandwidth of the transducer and the intensity of the illumination, are important factors. Near the limit of these factors, the performance of the film might be a factor.
> > > >>> I'm thinking of a theoretical device using analog audio recording on > > > >>> VD optical tracks containing the oldest film chemical composition. > > > > Blue takes up less space than green [for the same amount of data], so > > > > I'm guessing blue would make more efficient use of the film's length. > > > > This is because blue light is of shorter wavelength than green light. > > > > Per area, blue can represent more info than green.
> > > > What is the best wavelength of blue to use?
> > > You're confusing two different sorts of recording here. It's true that > > > in digital recording to optical discs the shorter wavelength of blue > > > light is an advantage (as in Blu-Ray vs. standard DVD), because that > > > style of recording looks at the presence or absence of individual "pits" > > > representing binary data, and blue light can be focused more tightly > > > onto smaller pits on the disc.
> > > This has almost nothing to do with variable-density audio recording on > > > film, in which analog audio signals are photographed as varying gray > > > tones on the track.
> > > Black-and-white film is inherently grainy; the various levels of gray in > > > a VD track are made up of varying densities of exposed-and-developed > > > grains -- starting out as crystals of a silver halide, then developed to > > > bits of metallic silver in the emulsion. On a microscopic scale, b/w > > > film is just that: opaque silver bits in a clear emulsion. It only > > > looks gray on a broader view, just as a halftoned newspaper photograph > > > made up of dots of black ink on paper simulates grayscales at ordinary > > > reading distance.
> > > So it's necessary for the soundtrack to be wide enough (usually at least > > > a couple of millimeters) that the reading process "looks at" a broad > > > enough area to average out the film grain. If you used a laser spot > > > pickup similar to the one in a DVD player to read a VD film soundtrack, > > > the output would be full of random noise as the individual grains passed > > > by the reader.
> > > And of course, to expose this wide a track, the sound recorder must > > > project the flickering light through a slit that's as wide as the track.
> > > In other words, the area you're looking at is so much larger than the > > > wavelength of light that the color of the light for recording or > > > playback doesn't matter.
> > > -Neil Midkiff
> > What determines the highest-frequency sound that can be recorded onto > > a VD optical track?- Hide quoted text -
> > - Show quoted text -
> The speed at which the film moves, the bandwidth of the transducer and > the intensity of the illumination, are important factors. Near the > limit of these factors, the performance of the film might be a factor.
You say intensity of illumination. Does that mean that a more intense light can allow for a higher-frequency than a less intense light?
By transducer, I assume your talking about the photoelectric cells that convert the optical signal playback from the film into an electric signal to be amplified and sent to a loudspeaker. Am I on the right track?
As for the tape speed, does the nyquist theorem apply? If so, what is the minimum tape speed required to record a sound of 1 Hz? IOW, how high of a frequency is allowed per speed? In devices where sampling- rates are used, the sample-rate must be at least 2x that maximum frequency of the input signal.
> > > > >>> I'm thinking of a theoretical device using analog audio recording on > > > > >>> VD optical tracks containing the oldest film chemical composition. > > > > > Blue takes up less space than green [for the same amount of data], so > > > > > I'm guessing blue would make more efficient use of the film's length. > > > > > This is because blue light is of shorter wavelength than green light. > > > > > Per area, blue can represent more info than green.
> > > > > What is the best wavelength of blue to use?
> > > > You're confusing two different sorts of recording here. It's true that > > > > in digital recording to optical discs the shorter wavelength of blue > > > > light is an advantage (as in Blu-Ray vs. standard DVD), because that > > > > style of recording looks at the presence or absence of individual "pits" > > > > representing binary data, and blue light can be focused more tightly > > > > onto smaller pits on the disc.
> > > > This has almost nothing to do with variable-density audio recording on > > > > film, in which analog audio signals are photographed as varying gray > > > > tones on the track.
> > > > Black-and-white film is inherently grainy; the various levels of gray in > > > > a VD track are made up of varying densities of exposed-and-developed > > > > grains -- starting out as crystals of a silver halide, then developed to > > > > bits of metallic silver in the emulsion. On a microscopic scale, b/w > > > > film is just that: opaque silver bits in a clear emulsion. It only > > > > looks gray on a broader view, just as a halftoned newspaper photograph > > > > made up of dots of black ink on paper simulates grayscales at ordinary > > > > reading distance.
> > > > So it's necessary for the soundtrack to be wide enough (usually at least > > > > a couple of millimeters) that the reading process "looks at" a broad > > > > enough area to average out the film grain. If you used a laser spot > > > > pickup similar to the one in a DVD player to read a VD film soundtrack, > > > > the output would be full of random noise as the individual grains passed > > > > by the reader.
> > > > And of course, to expose this wide a track, the sound recorder must > > > > project the flickering light through a slit that's as wide as the track.
> > > > In other words, the area you're looking at is so much larger than the > > > > wavelength of light that the color of the light for recording or > > > > playback doesn't matter.
> > > > -Neil Midkiff
> > > What determines the highest-frequency sound that can be recorded onto > > > a VD optical track?- Hide quoted text -
> > > - Show quoted text -
> > The speed at which the film moves, the bandwidth of the transducer and > > the intensity of the illumination, are important factors. Near the > > limit of these factors, the performance of the film might be a factor.
> You say intensity of illumination. Does that mean that a more intense > light can allow for a higher-frequency than a less intense light?
> By transducer, I assume your talking about the photoelectric cells > that convert the optical signal playback from the film into an > electric signal to be amplified and sent to a loudspeaker. Am I on the > right track?
> As for the tape speed, does the nyquist theorem apply? If so, what is > the minimum tape speed required to record a sound of 1 Hz? IOW, how > high of a frequency is allowed per speed? In devices where sampling- > rates are used, the sample-rate must be at least 2x that maximum > frequency of the input signal.
Proof positive that a little information can do a lot of harm.
GreenXenon wrote: > On May 13, 8:43 am, Peter <w2...@hotmail.com> wrote: >> On May 12, 10:42 pm, GreenXenon <glucege...@gmail.com> wrote:
>>> On May 12, 1:23 pm, Neil Midkiff <nmidk...@earthlink.net> wrote: >>>> GreenXenon wrote: >>>>>> GreenXenon wrote: >>>>>>> I'm thinking of a theoretical device using analog audio recording on >>>>>>> VD optical tracks containing the oldest film chemical composition. >>>>> Blue takes up less space than green [for the same amount of data], so >>>>> I'm guessing blue would make more efficient use of the film's length. >>>>> This is because blue light is of shorter wavelength than green light. >>>>> Per area, blue can represent more info than green. >>>>> What is the best wavelength of blue to use? >>>> You're confusing two different sorts of recording here. It's true that >>>> in digital recording to optical discs the shorter wavelength of blue >>>> light is an advantage (as in Blu-Ray vs. standard DVD), because that >>>> style of recording looks at the presence or absence of individual "pits" >>>> representing binary data, and blue light can be focused more tightly >>>> onto smaller pits on the disc. >>>> This has almost nothing to do with variable-density audio recording on >>>> film, in which analog audio signals are photographed as varying gray >>>> tones on the track. >>>> Black-and-white film is inherently grainy; the various levels of gray in >>>> a VD track are made up of varying densities of exposed-and-developed >>>> grains -- starting out as crystals of a silver halide, then developed to >>>> bits of metallic silver in the emulsion. On a microscopic scale, b/w >>>> film is just that: opaque silver bits in a clear emulsion. It only >>>> looks gray on a broader view, just as a halftoned newspaper photograph >>>> made up of dots of black ink on paper simulates grayscales at ordinary >>>> reading distance. >>>> So it's necessary for the soundtrack to be wide enough (usually at least >>>> a couple of millimeters) that the reading process "looks at" a broad >>>> enough area to average out the film grain. If you used a laser spot >>>> pickup similar to the one in a DVD player to read a VD film soundtrack, >>>> the output would be full of random noise as the individual grains passed >>>> by the reader. >>>> And of course, to expose this wide a track, the sound recorder must >>>> project the flickering light through a slit that's as wide as the track. >>>> In other words, the area you're looking at is so much larger than the >>>> wavelength of light that the color of the light for recording or >>>> playback doesn't matter. >>>> -Neil Midkiff >>> What determines the highest-frequency sound that can be recorded onto >>> a VD optical track?
>> The speed at which the film moves, the bandwidth of the transducer and >> the intensity of the illumination, are important factors. Near the >> limit of these factors, the performance of the film might be a factor.
> You say intensity of illumination. Does that mean that a more intense > light can allow for a higher-frequency than a less intense light?
> By transducer, I assume your talking about the photoelectric cells > that convert the optical signal playback from the film into an > electric signal to be amplified and sent to a loudspeaker. Am I on the > right track?
> As for the tape speed, does the nyquist theorem apply? If so, what is > the minimum tape speed required to record a sound of 1 Hz? IOW, how > high of a frequency is allowed per speed? In devices where sampling- > rates are used, the sample-rate must be at least 2x that maximum > frequency of the input signal.
Sorry, my branch of the free university has closed down for the month.
A simple "Thank you" now and then might go a long way towards paying your tuition for the next round of courses.
Until then, you might try actually reading a book at the public library.
>> > > >>> I'm thinking of a theoretical device using analog >> > > >>> audio recording on >> > > >>> VD optical tracks containing the oldest film >> > > >>> chemical composition. >> > > > Blue takes up less space than green [for the same >> > > > amount of data], so >> > > > I'm guessing blue would make more efficient use of >> > > > the film's length. >> > > > This is because blue light is of shorter wavelength >> > > > than green light. >> > > > Per area, blue can represent more info than green.
>> > > > What is the best wavelength of blue to use?
>> > > You're confusing two different sorts of recording >> > > here. It's true that >> > > in digital recording to optical discs the shorter >> > > wavelength of blue >> > > light is an advantage (as in Blu-Ray vs. standard >> > > DVD), because that >> > > style of recording looks at the presence or absence >> > > of individual "pits" >> > > representing binary data, and blue light can be >> > > focused more tightly >> > > onto smaller pits on the disc.
>> > > This has almost nothing to do with variable-density >> > > audio recording on >> > > film, in which analog audio signals are photographed >> > > as varying gray >> > > tones on the track.
>> > > Black-and-white film is inherently grainy; the >> > > various levels of gray in >> > > a VD track are made up of varying densities of >> > > exposed-and-developed >> > > grains -- starting out as crystals of a silver >> > > halide, then developed to >> > > bits of metallic silver in the emulsion. On a >> > > microscopic scale, b/w >> > > film is just that: opaque silver bits in a clear >> > > emulsion. It only >> > > looks gray on a broader view, just as a halftoned >> > > newspaper photograph >> > > made up of dots of black ink on paper simulates >> > > grayscales at ordinary >> > > reading distance.
>> > > So it's necessary for the soundtrack to be wide >> > > enough (usually at least >> > > a couple of millimeters) that the reading process >> > > "looks at" a broad >> > > enough area to average out the film grain. If you >> > > used a laser spot >> > > pickup similar to the one in a DVD player to read a >> > > VD film soundtrack, >> > > the output would be full of random noise as the >> > > individual grains passed >> > > by the reader.
>> > > And of course, to expose this wide a track, the sound >> > > recorder must >> > > project the flickering light through a slit that's as >> > > wide as the track.
>> > > In other words, the area you're looking at is so much >> > > larger than the >> > > wavelength of light that the color of the light for >> > > recording or >> > > playback doesn't matter.
>> > > -Neil Midkiff
>> > What determines the highest-frequency sound that can be >> > recorded onto >> > a VD optical track?- Hide quoted text -
>> > - Show quoted text -
>> The speed at which the film moves, the bandwidth of the >> transducer and >> the intensity of the illumination, are important factors. >> Near the >> limit of these factors, the performance of the film might >> be a factor.
> You say intensity of illumination. Does that mean that a > more intense > light can allow for a higher-frequency than a less intense > light?
> By transducer, I assume your talking about the > photoelectric cells > that convert the optical signal playback from the film > into an > electric signal to be amplified and sent to a loudspeaker. > Am I on the > right track?
> As for the tape speed, does the nyquist theorem apply? If > so, what is > the minimum tape speed required to record a sound of 1 Hz? > IOW, how > high of a frequency is allowed per speed? In devices where > sampling- > rates are used, the sample-rate must be at least 2x that > maximum > frequency of the input signal.
Ultimately the frequency limit if the resolution of the system. Film is probably the limiting factor here but there are other contributors. Plus, film resolution is not a simple matter. As far as transducers are concerned the limit is probably the slit length of the reproducer, assuming a conventional system. Most film resolution is given as a contrast limit, usually as the 50% point. This may not work for sound recording. BTW, the limit is the same whether the record is variable density or variable width. The _practical_ limit for threatrical motion pictures was around 6000 Hz but that was a compromise taking into account a great many factors. The Bell Telephone Laboratories did experiments in the late 1930s using especially constructed modulators and reproducers that were flat to about 15,000 but his has never been practical for normal release prints. Experimentally, its certainly possible to obtain a limit of 15Khz on 35mm film moving at 90 feet/minute (24 FPS) and, in fact, on 16mm film at 60 feet/minute (24 FPS). The use of a laser recorder to write directly on the film would eliminate losses due to the mecanical modulator, the recording lens, etc. All this has been researched and reported. Such a system would probably have better performance as a pulse modulated system rather than direct analogue recording of whatever type. I think you need to start doing some research on your own because the questions you ask are all answered in the literature. I recommended the Journal of the SMPTE and its still the best place to start.
I will also say that I take most posts seriously. This one may be serious or a troll. The fact that its cross-posted to six different news groups tends to indicate troll but I give it the benefit of my doubt.
--
-- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com
>> > > >>> I'm thinking of a theoretical device using analog >> > > >>> audio recording on >> > > >>> VD optical tracks containing the oldest film >> > > >>> chemical composition. >> > > > Blue takes up less space than green [for the same >> > > > amount of data], so >> > > > I'm guessing blue would make more efficient use of >> > > > the film's length. >> > > > This is because blue light is of shorter wavelength >> > > > than green light. >> > > > Per area, blue can represent more info than green.
>> > > > What is the best wavelength of blue to use?
>> > > You're confusing two different sorts of recording >> > > here. It's true that >> > > in digital recording to optical discs the shorter >> > > wavelength of blue >> > > light is an advantage (as in Blu-Ray vs. standard >> > > DVD), because that >> > > style of recording looks at the presence or absence >> > > of individual "pits" >> > > representing binary data, and blue light can be >> > > focused more tightly >> > > onto smaller pits on the disc.
>> > > This has almost nothing to do with variable-density >> > > audio recording on >> > > film, in which analog audio signals are photographed >> > > as varying gray >> > > tones on the track.
>> > > Black-and-white film is inherently grainy; the >> > > various levels of gray in >> > > a VD track are made up of varying densities of >> > > exposed-and-developed >> > > grains -- starting out as crystals of a silver >> > > halide, then developed to >> > > bits of metallic silver in the emulsion. On a >> > > microscopic scale, b/w >> > > film is just that: opaque silver bits in a clear >> > > emulsion. It only >> > > looks gray on a broader view, just as a halftoned >> > > newspaper photograph >> > > made up of dots of black ink on paper simulates >> > > grayscales at ordinary >> > > reading distance.
>> > > So it's necessary for the soundtrack to be wide >> > > enough (usually at least >> > > a couple of millimeters) that the reading process >> > > "looks at" a broad >> > > enough area to average out the film grain. If you >> > > used a laser spot >> > > pickup similar to the one in a DVD player to read a >> > > VD film soundtrack, >> > > the output would be full of random noise as the >> > > individual grains passed >> > > by the reader.
>> > > And of course, to expose this wide a track, the sound >> > > recorder must >> > > project the flickering light through a slit that's as >> > > wide as the track.
>> > > In other words, the area you're looking at is so much >> > > larger than the >> > > wavelength of light that the color of the light for >> > > recording or >> > > playback doesn't matter.
>> > > -Neil Midkiff
>> > What determines the highest-frequency sound that can be >> > recorded onto >> > a VD optical track?- Hide quoted text -
>> > - Show quoted text -
>> The speed at which the film moves, the bandwidth of the >> transducer and >> the intensity of the illumination, are important factors. >> Near the >> limit of these factors, the performance of the film might >> be a factor.
> You say intensity of illumination. Does that mean that a > more intense > light can allow for a higher-frequency than a less intense > light?
> By transducer, I assume your talking about the > photoelectric cells > that convert the optical signal playback from the film > into an > electric signal to be amplified and sent to a loudspeaker. > Am I on the > right track?
> As for the tape speed, does the nyquist theorem apply? If > so, what is > the minimum tape speed required to record a sound of 1 Hz? > IOW, how > high of a frequency is allowed per speed? In devices where > sampling- > rates are used, the sample-rate must be at least 2x that > maximum > frequency of the input signal.
Since analogue recording does not involve sampling the Nyquist criteria as applied to sampling systems does not directly apply. However, there is a similar limitation based on the slit length (length, width and height are releated to film movement, slit length here means its dimention in the direction of film motion). When the slit length is equal to a half wavelength there is cancellation of the output. So, just as in analogue magnetic recording there can be a series of peaks and dips in output as the frequency is increased (sinX/X function). The recorder can do something similar but the effective slit length is dependant on the type of recorder. For moving mirror recorders as used by RCA the slit is constant for both variable width and variable density records. For records made by ribbon light valves as used by Western Electric/Westrex the slit length varies with the sound intensity so that these are known as variable exposure time recorders where the moving mirror type has constant exposure time. Thus the effect of film reciprocity failure is different for the two systems.
I don't understand what the previous poster was getting at by stating that the intensity of light affected maximum frequency, perhaps he will elucidate.
-- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com
> GreenXenon wrote: > > On May 13, 8:43 am, Peter <w2...@hotmail.com> wrote: > >> On May 12, 10:42 pm, GreenXenon <glucege...@gmail.com> wrote:
> >>> On May 12, 1:23 pm, Neil Midkiff <nmidk...@earthlink.net> wrote: > >>>> GreenXenon wrote: > >>>>>> GreenXenon wrote: > >>>>>>> I'm thinking of a theoretical device using analog audio recording on > >>>>>>> VD optical tracks containing the oldest film chemical composition. > >>>>> Blue takes up less space than green [for the same amount of data], so > >>>>> I'm guessing blue would make more efficient use of the film's length. > >>>>> This is because blue light is of shorter wavelength than green light. > >>>>> Per area, blue can represent more info than green. > >>>>> What is the best wavelength of blue to use? > >>>> You're confusing two different sorts of recording here. It's true that > >>>> in digital recording to optical discs the shorter wavelength of blue > >>>> light is an advantage (as in Blu-Ray vs. standard DVD), because that > >>>> style of recording looks at the presence or absence of individual "pits" > >>>> representing binary data, and blue light can be focused more tightly > >>>> onto smaller pits on the disc. > >>>> This has almost nothing to do with variable-density audio recording on > >>>> film, in which analog audio signals are photographed as varying gray > >>>> tones on the track. > >>>> Black-and-white film is inherently grainy; the various levels of gray in > >>>> a VD track are made up of varying densities of exposed-and-developed > >>>> grains -- starting out as crystals of a silver halide, then developed to > >>>> bits of metallic silver in the emulsion. On a microscopic scale, b/w > >>>> film is just that: opaque silver bits in a clear emulsion. It only > >>>> looks gray on a broader view, just as a halftoned newspaper photograph > >>>> made up of dots of black ink on paper simulates grayscales at ordinary > >>>> reading distance. > >>>> So it's necessary for the soundtrack to be wide enough (usually at least > >>>> a couple of millimeters) that the reading process "looks at" a broad > >>>> enough area to average out the film grain. If you used a laser spot > >>>> pickup similar to the one in a DVD player to read a VD film soundtrack, > >>>> the output would be full of random noise as the individual grains passed > >>>> by the reader. > >>>> And of course, to expose this wide a track, the sound recorder must > >>>> project the flickering light through a slit that's as wide as the track. > >>>> In other words, the area you're looking at is so much larger than the > >>>> wavelength of light that the color of the light for recording or > >>>> playback doesn't matter. > >>>> -Neil Midkiff > >>> What determines the highest-frequency sound that can be recorded onto > >>> a VD optical track?
> >> The speed at which the film moves, the bandwidth of the transducer and > >> the intensity of the illumination, are important factors. Near the > >> limit of these factors, the performance of the film might be a factor.
> > You say intensity of illumination. Does that mean that a more intense > > light can allow for a higher-frequency than a less intense light?
> > By transducer, I assume your talking about the photoelectric cells > > that convert the optical signal playback from the film into an > > electric signal to be amplified and sent to a loudspeaker. Am I on the > > right track?
> > As for the tape speed, does the nyquist theorem apply? If so, what is > > the minimum tape speed required to record a sound of 1 Hz? IOW, how > > high of a frequency is allowed per speed? In devices where sampling- > > rates are used, the sample-rate must be at least 2x that maximum > > frequency of the input signal.
> Sorry, my branch of the free university has closed down for the month.
> A simple "Thank you" now and then might go a long way towards paying > your tuition for the next round of courses.
> Until then, you might try actually reading a book at the public library.
> -Neil Midkiff
Thanks for your assistance. Sorry, if my posts were offensive to you.
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