Wavelength response of first type of film with sound?

[GreenXenon]

Hi:

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

[Pat]

Post by GreenXenon
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.

[Savageduck]

Post by GreenXenon
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?

[Richard Knoppow]

Post by GreenXenon
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
***@ix.netcom.com

[Neil Midkiff]

Post by GreenXenon
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.

Post by GreenXenon
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.

Post by GreenXenon
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.

-Neil Midkiff

[GreenXenon]

Post by Neil Midkiff

Post by GreenXenon
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?

[David Nebenzahl]

Post by GreenXenon
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.

[Neil Midkiff]

Post by GreenXenon

Post by GreenXenon
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

[GreenXenon]

Post by Neil Midkiff

Post by GreenXenon

Post by GreenXenon
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?

[Peter]

Post by GreenXenon

Post by GreenXenon

Post by GreenXenon
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 -

[Peter]

Post by GreenXenon

Post by GreenXenon

Post by GreenXenon
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.

[GreenXenon]

Post by Peter

Post by GreenXenon

Post by Neil Midkiff

Post by GreenXenon

Post by GreenXenon
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.

[J. Theakston]

Post by GreenXenon

Post by Peter

Post by GreenXenon

Post by GreenXenon

Post by GreenXenon
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.

J. Theakston

[Neil Midkiff]

Post by GreenXenon

Post by Peter

Post by GreenXenon

Post by Neil Midkiff

Post by GreenXenon

Post by GreenXenon
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

[GreenXenon]

Post by Neil Midkiff

Post by GreenXenon

Post by Peter

Post by GreenXenon

Post by Neil Midkiff

Post by GreenXenon

Post by GreenXenon
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.

[Richard Knoppow]

Post by GreenXenon

Post by Peter

On May 12, 1:23 pm, Neil Midkiff

Post by Neil Midkiff

Post by GreenXenon

Post by GreenXenon
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]

Post by GreenXenon

Post by Peter

On May 12, 1:23 pm, Neil Midkiff

Post by Neil Midkiff

Post by GreenXenon

Post by GreenXenon
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
***@ix.netcom.com

[Richard Knoppow]

Post by GreenXenon

Post by Neil Midkiff

Post by GreenXenon
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.