تويت
التصوير الفوتوغرافي الحديث
صنع صور متحركة للتلفزيون
إضافة الصوت
مسار الصوت البصري
OPTICAL SOUND TRACK
This is the professional sound system used throughout the industry . In this system , the sound track is a narrow band running next to the picture for its entire length . The film itself , whether positive or negative , does not have the sound track prior to exposure . The track is printed there photographically .
VARIABLE AREA OR VARIABLE DENSITY ? There are two types of optical sound tracks : the variable area and the variable density . Since the variable area is the one most commonly used , we will describe it briefly here .
In this system , a tiny beam of light is aimed at a small mirror and reflected from it to produce a narrow spot of light on the film . In the process of recording , the sound is picked up by the microphone and converted into tiny pulsating currents of electricity . These pulsating currents cause the tiny mirror to vibrate in much the same way as voice currents cause the diaphragm of a loudspeaker to vibrate . The vibrating mirror causes the beam of light to oscillate in exact step with the voice currents .
While this is going on the film is moving through the recording mechanism and is being exposed to the beam of oscillating light . When the exposed film is processed , the result is a jagged black stripe running the full length of the film . The wiggles in this stripe correspond exactly to the vibrations of the original sound . This sound track , greatly magnified for clarity , is shown in Figure 3 on page 18 .
The sound track is converted back to sound in the projector . There another beam of light passes through the track and is modulated by the variable area of the track . This modulated beam of light is picked up by a photocell and converted into a pulsating electric current . This current is amplified and fed into the loudspeaker where it becomes sound again .
TABLE I. SEPARATION BETWEEN PICTURE AND SOUND
TYPICAL SOUND MOTION PICTURE PROJECTOR
The projector is a motion picture camera in reverse . The pull - down claw , shutter , and inter mittent action are the same as in the camera . The sound being picked up by the sound reproduction system at A is the sound for the frame being projected , B. This is the reason for the sound track being ahead of the picture .
This diagrammatic view of a sound movie projector shows why the sound track must be ahead of the picture . The separation differs according to film size and type of sound track , as indicated in the table at the top of this page .
- Figure 3 How a variable area optical sound track is printed on film . Light from the light source passes through a wedge shaped mask before striking an oscillating mirror . Electrical impulses cause the mirror to oscillate and move the wedge shaped beam up and down across a narrow slit . This causes the beam of light to become wider and narrower so that it produces a bilateral track on the sound tape . Less noise slants the mirror upwards so that less light strikes the negative and the track becomes narrower at this point . More noise slants the mirror down and the track becomes wider at this point .
The two types of variable area optical sound tracks in use in the movie industry today . At the left is a bilateral bias sound track , and at the right is a push - pull Class B sound track . The bilateral track is printed on film as described above .
Since optical sound is an integral part of the film itself , it cannot get out of synchronization . Furthermore , it can be printed on the master negative so that every released print run off from it is identical in all respects , including the sound track .
SINGLE OR DOUBLE SYSTEM SOUND ? There are two types of optical sound systems - the single and the double . In the single system , the sound track is recorded on the film while it is being run through the camera . This system is sometimes used for short runs and on - the - spot interviews where very little editing is to be done . The exposed film is processed , cut down to length and made part of the news reel which is then put on the air just about as it was shot . When a more finished product is required , the double system is necessary . In this system , the sound is recorded on a separate perforated magnetic tape . Synchronous motors are used so that the recording tape travels at exactly the same speed as the film travels through the camera . In addition , the perforations on the tape prevent . slippage and provide a further safeguard against loss of synchronization . After the working negative is cut and edited , the sound track is also edited to match and a release print made which contains both picture and sound .
A camera built for the purpose of news coverage . It is a single system 16mm sound movie camera . The term single system means that the sound is re corded on the film as the film is being exposed . This type of camera can re cord the sound either optically or mag netically .
Courtesy of Mitchell Camera Corp.
Although the normal procedure is to edit the picture first and then cut the sound track to match , there are times when the reversed procedure is followed . For example , when filming a commercial it is the sound track which is of major importance . Great pains have been taken by the advertising agency in composing the all - important commentary which is the heart of the commercial . It has been carefully timed to the split second , and it cannot be cut or changed in any way . In such cases the sound track is usually recorded first , and then the picture carefully cut and edited to match .
صنع صور متحركة للتلفزيون
إضافة الصوت
مسار الصوت البصري
OPTICAL SOUND TRACK
This is the professional sound system used throughout the industry . In this system , the sound track is a narrow band running next to the picture for its entire length . The film itself , whether positive or negative , does not have the sound track prior to exposure . The track is printed there photographically .
VARIABLE AREA OR VARIABLE DENSITY ? There are two types of optical sound tracks : the variable area and the variable density . Since the variable area is the one most commonly used , we will describe it briefly here .
In this system , a tiny beam of light is aimed at a small mirror and reflected from it to produce a narrow spot of light on the film . In the process of recording , the sound is picked up by the microphone and converted into tiny pulsating currents of electricity . These pulsating currents cause the tiny mirror to vibrate in much the same way as voice currents cause the diaphragm of a loudspeaker to vibrate . The vibrating mirror causes the beam of light to oscillate in exact step with the voice currents .
While this is going on the film is moving through the recording mechanism and is being exposed to the beam of oscillating light . When the exposed film is processed , the result is a jagged black stripe running the full length of the film . The wiggles in this stripe correspond exactly to the vibrations of the original sound . This sound track , greatly magnified for clarity , is shown in Figure 3 on page 18 .
The sound track is converted back to sound in the projector . There another beam of light passes through the track and is modulated by the variable area of the track . This modulated beam of light is picked up by a photocell and converted into a pulsating electric current . This current is amplified and fed into the loudspeaker where it becomes sound again .
TABLE I. SEPARATION BETWEEN PICTURE AND SOUND
TYPICAL SOUND MOTION PICTURE PROJECTOR
The projector is a motion picture camera in reverse . The pull - down claw , shutter , and inter mittent action are the same as in the camera . The sound being picked up by the sound reproduction system at A is the sound for the frame being projected , B. This is the reason for the sound track being ahead of the picture .
This diagrammatic view of a sound movie projector shows why the sound track must be ahead of the picture . The separation differs according to film size and type of sound track , as indicated in the table at the top of this page .
- Figure 3 How a variable area optical sound track is printed on film . Light from the light source passes through a wedge shaped mask before striking an oscillating mirror . Electrical impulses cause the mirror to oscillate and move the wedge shaped beam up and down across a narrow slit . This causes the beam of light to become wider and narrower so that it produces a bilateral track on the sound tape . Less noise slants the mirror upwards so that less light strikes the negative and the track becomes narrower at this point . More noise slants the mirror down and the track becomes wider at this point .
The two types of variable area optical sound tracks in use in the movie industry today . At the left is a bilateral bias sound track , and at the right is a push - pull Class B sound track . The bilateral track is printed on film as described above .
Since optical sound is an integral part of the film itself , it cannot get out of synchronization . Furthermore , it can be printed on the master negative so that every released print run off from it is identical in all respects , including the sound track .
SINGLE OR DOUBLE SYSTEM SOUND ? There are two types of optical sound systems - the single and the double . In the single system , the sound track is recorded on the film while it is being run through the camera . This system is sometimes used for short runs and on - the - spot interviews where very little editing is to be done . The exposed film is processed , cut down to length and made part of the news reel which is then put on the air just about as it was shot . When a more finished product is required , the double system is necessary . In this system , the sound is recorded on a separate perforated magnetic tape . Synchronous motors are used so that the recording tape travels at exactly the same speed as the film travels through the camera . In addition , the perforations on the tape prevent . slippage and provide a further safeguard against loss of synchronization . After the working negative is cut and edited , the sound track is also edited to match and a release print made which contains both picture and sound .
A camera built for the purpose of news coverage . It is a single system 16mm sound movie camera . The term single system means that the sound is re corded on the film as the film is being exposed . This type of camera can re cord the sound either optically or mag netically .
Courtesy of Mitchell Camera Corp.
Although the normal procedure is to edit the picture first and then cut the sound track to match , there are times when the reversed procedure is followed . For example , when filming a commercial it is the sound track which is of major importance . Great pains have been taken by the advertising agency in composing the all - important commentary which is the heart of the commercial . It has been carefully timed to the split second , and it cannot be cut or changed in any way . In such cases the sound track is usually recorded first , and then the picture carefully cut and edited to match .
تعليق