تويت
التصوير الفوتوغرافي الحديث
الفلاش والتصوير الضوئي المتوفر
الجزء الأول - تصوير فلاش
أنواع الفلاش
Part -1- Flash Photography
Flash photography is probably the most commonly used means of shooting pictures after dark - that is understandable because flash is convenient and simple . to use and relatively inexpensive . Its sole application , however , is not limited to taking pictures in the dark . Flash fill - in on bright sunny days is a very useful way of improving picture quality .
You will learn more about this and other flash applications in this Assignment . First , however , we will review some of the basic principles of flashbulbs and electronic flash units . You will learn something about how they operate , why synchronization is necessary , and what reflectors and power sources are best . You will also learn how to determine proper exposure with flash equipment .
The seven principle set - ups for flash lighting are discussed . You will learn how to use flash fill - in for daylight pictures . Knowing and using this technique may make a world of difference in your outdoor photography . We will also cover shooting color with flash .
TYPES OF FLASH
There are two types of flash lamps . The most widely used , and by far the simplest , is the regular flashbulb used only once and thrown away . The other is the electronic flash in which a heavy current is passed for an instant through a gas - filled tube . An intense burst of light is produced during this short fraction of a second . While the equipment for the two types of flash is very different , the flash units themselves are used in much the same manner . We will discuss the regular flashbulb or flash lamp first . The later sections on how to take successful pictures apply to both types of flash .
FLASHBULBS
Just what is a flashbulb , and how does it work ? Essentially , it is a small glass bulb , something like a small light bulb , except that it contains a filament , a primer powder or paste around the filament leads , and a quantity of fine metal wire or foil . The bulb is filled with oxygen . When eleétric current , usually from a flashlight battery , is passed through the bulb , the filament gets white hot , just as in an ordinary light bulb . This ignites the primer . The burning primer , in turn , ignites the metal foil or wire , which immediately burns in the oxygen - filled bulb .. The burning foil or wire produces an intense flash of light . Though this action sounds complex , the complete series of events occurs in about 1/25 second .
TYPES OF FLASHBULBS . Flashbulbs come in a large selection of sizes and styles to serve a wide variety of uses . The amount of light emitted , the length of time during which it is emitted , and the time elapsing between pressing the contact button and the actual flash are all important factors which determine how the flashbulb can best be used . For close - up work , the bulbs are quite small . For wide coverage where large amounts of light are needed , as for outdoor sports , the bulbs are as large as regular light bulbs .
Some bulbs burn very quickly ; these are generally designed for the simplest cameras without accurate synchronization . Others are designed to burn more slowly , so the lamp can be fired and a very short exposure made while the lamp is burning . This requires extremely accurate synchronization between the opening of the shutter and the flashing of the lamp , but it permits the photographer to make very short exposures and to stop motion ..
Before we go into the use of the flashbulb , we must briefly discuss some of the terms used in determining its operating characteristics . The first of these terms is lumen .
The lumen is a unit of light . It is used to measure the intensity of light coming from any source . The total amount of light from any source is determined by multiplying the intensity ( lumens ) of the light by the length of time ( seconds ) the light is shining . Therefore , a flashbulb's light output ( how much and for how long ) is expressed in lumen - seconds .
Another important characteristic of a flashbulb is the intensity of its light when burning at peak brilliance . This is called the peak lumens . Peak lumens and lumen - seconds are not the same and cannot be used interchangeably . The more commonly used flashbulbs and their light output ( also called time - lag curves ) are illustrated in Figure 1 , for G - E bulbs . Other makes of bulbs have substantially the same characteristics . Note the light output starts a short time after electric contact is made ; then rises quite rapidly to a peak and finally dies down to zero again after the flash material is exhausted . Peak lumens are measured by the height of the curve at its peak , while lumen - seconds are measured by the total area under the curve . ( Figure 1 )
TIME - LIGHT CURVES FOR G - E FLASHBULBS
A time - light curve shows the intensity of light at each instant of time after electrical contact is made . The inten sity of light is plotted vertically on the chart and is measured in millions of lumens . The time scale is read horizontally and is measured in Milliseconds ( 1 milli . second - 1 / 1000th second ) .
THE TERM " LUMEN - SECONDS " means the total amount of light emitted by the flashbulb .
TIME - TO - PEAK is the expression used to indicate the number of milliseconds it takes a flashbulb to reach its highest intensity after electrical contact has been made .
A millisecond or one thousandth of a second is the time interval used in measuring flash characteristics . Time lag is the time that elapses between the closing of the electrical circuit and the peak of the flash . For most flashbulbs this is slightly less than 20 milliseconds , which is the same as .020 seconds ( 1/50 second ) . Flashbulbs are generally classified according to their time lag . The principle classes are the intermediate peak ( M - 2 , M - 3 , M - 25 and AG - 1 ) , the medium peak ( M ) , the slow peak ( S ) , and the very slow peak for focal plane shutters ( FP ) .
Flashcubes and AG - I Flashbulbs . These are midget lamps which reach maximum light output about 15 milliseconds after electrical contact is made . Both the flashcube and the AG - 1 flashbulb are quite small , and every effort has been made to reduce their size and weight . The AG - 1 , for example , has no base the wires which carry the current simply come out through a glass seal at the bottom of the bulb . Each flashcube is really four tiny flashbulbs in one . Each of the tiny flash units of the flashcube has its own highly polished reflector and four of them are sealed into a cube of clear plastic , so that there is a lamp for each of the four sides . The contact terminals are at the bottom of the cube .
The flashcube was designed primarily for use with small automatic cameras used by the novice , and the sockets built into the cameras are equipped with spring mechanisms which rotate the cube one - quarter turn automatically after each flash until all four flash units are fired . Flashcube adapters and complete flashguns are available , so that flashcubes may be used with conventional flashguns .
The high efficiency of the reflectors used with both the flashcubes and the AG - 1 flashbulbs compensates to a considerable degree for the low light output of these tiny lamps . Because of their relatively short peak interval or time lag , these flashbulbs can be used quite satisfactorily without synchronized shutters by setting the shutter to 1/25 or 1/30 second . This is explained more fully later in the Assignment .
Class M Flashbulbs . These are medium peak lamps , reaching maximum light output in 18 to 20 milliseconds after current is applied . The condition of the batteries has considerable influence on the time of peak - it may be as short as 16 milliseconds with absolutely fresh batteries of the proper type , or as long as 25 milliseconds if the batteries are run down . Therefore , it is important to keep flash batteries fresh at all times .
Class S Flashbulbs . These large lamps are used primarily for open flash work , so their time to peak brilliance is about 30 milliseconds after contact . They cannot be used with synchronized shutters because of their long time lag .
Class FP Flashbulbs . These lamps are designed for use with focal plane shutters . A focal plane shutter must move across the entire length of the film while making the exposure , even though its slit may be quite narrow . In the average 35mm camera , this takes about 20 milliseconds ( 1/50 second ) . The flash lamp must , therefore , give out a fairly uniform light throughout the time the shutter is moving , even though the actual exposure may be only 1/1000 second . If the light is not uniform for this 1/50 second , the exposure for one part of the film will not be the same as for others .
The FP type of flash lamps are made so that illumination rises to a maximum in from 15 to 20 milliseconds , holds constant at this level for another 20 milliseconds ( 40 for large lamps ) , and then dies out . This is shown in the timelight curves for the G - E No. 6 and No. 31 flashbulbs in Figure 1 .
الفلاش والتصوير الضوئي المتوفر
الجزء الأول - تصوير فلاش
أنواع الفلاش
Part -1- Flash Photography
Flash photography is probably the most commonly used means of shooting pictures after dark - that is understandable because flash is convenient and simple . to use and relatively inexpensive . Its sole application , however , is not limited to taking pictures in the dark . Flash fill - in on bright sunny days is a very useful way of improving picture quality .
You will learn more about this and other flash applications in this Assignment . First , however , we will review some of the basic principles of flashbulbs and electronic flash units . You will learn something about how they operate , why synchronization is necessary , and what reflectors and power sources are best . You will also learn how to determine proper exposure with flash equipment .
The seven principle set - ups for flash lighting are discussed . You will learn how to use flash fill - in for daylight pictures . Knowing and using this technique may make a world of difference in your outdoor photography . We will also cover shooting color with flash .
TYPES OF FLASH
There are two types of flash lamps . The most widely used , and by far the simplest , is the regular flashbulb used only once and thrown away . The other is the electronic flash in which a heavy current is passed for an instant through a gas - filled tube . An intense burst of light is produced during this short fraction of a second . While the equipment for the two types of flash is very different , the flash units themselves are used in much the same manner . We will discuss the regular flashbulb or flash lamp first . The later sections on how to take successful pictures apply to both types of flash .
FLASHBULBS
Just what is a flashbulb , and how does it work ? Essentially , it is a small glass bulb , something like a small light bulb , except that it contains a filament , a primer powder or paste around the filament leads , and a quantity of fine metal wire or foil . The bulb is filled with oxygen . When eleétric current , usually from a flashlight battery , is passed through the bulb , the filament gets white hot , just as in an ordinary light bulb . This ignites the primer . The burning primer , in turn , ignites the metal foil or wire , which immediately burns in the oxygen - filled bulb .. The burning foil or wire produces an intense flash of light . Though this action sounds complex , the complete series of events occurs in about 1/25 second .
TYPES OF FLASHBULBS . Flashbulbs come in a large selection of sizes and styles to serve a wide variety of uses . The amount of light emitted , the length of time during which it is emitted , and the time elapsing between pressing the contact button and the actual flash are all important factors which determine how the flashbulb can best be used . For close - up work , the bulbs are quite small . For wide coverage where large amounts of light are needed , as for outdoor sports , the bulbs are as large as regular light bulbs .
Some bulbs burn very quickly ; these are generally designed for the simplest cameras without accurate synchronization . Others are designed to burn more slowly , so the lamp can be fired and a very short exposure made while the lamp is burning . This requires extremely accurate synchronization between the opening of the shutter and the flashing of the lamp , but it permits the photographer to make very short exposures and to stop motion ..
Before we go into the use of the flashbulb , we must briefly discuss some of the terms used in determining its operating characteristics . The first of these terms is lumen .
The lumen is a unit of light . It is used to measure the intensity of light coming from any source . The total amount of light from any source is determined by multiplying the intensity ( lumens ) of the light by the length of time ( seconds ) the light is shining . Therefore , a flashbulb's light output ( how much and for how long ) is expressed in lumen - seconds .
Another important characteristic of a flashbulb is the intensity of its light when burning at peak brilliance . This is called the peak lumens . Peak lumens and lumen - seconds are not the same and cannot be used interchangeably . The more commonly used flashbulbs and their light output ( also called time - lag curves ) are illustrated in Figure 1 , for G - E bulbs . Other makes of bulbs have substantially the same characteristics . Note the light output starts a short time after electric contact is made ; then rises quite rapidly to a peak and finally dies down to zero again after the flash material is exhausted . Peak lumens are measured by the height of the curve at its peak , while lumen - seconds are measured by the total area under the curve . ( Figure 1 )
TIME - LIGHT CURVES FOR G - E FLASHBULBS
A time - light curve shows the intensity of light at each instant of time after electrical contact is made . The inten sity of light is plotted vertically on the chart and is measured in millions of lumens . The time scale is read horizontally and is measured in Milliseconds ( 1 milli . second - 1 / 1000th second ) .
THE TERM " LUMEN - SECONDS " means the total amount of light emitted by the flashbulb .
TIME - TO - PEAK is the expression used to indicate the number of milliseconds it takes a flashbulb to reach its highest intensity after electrical contact has been made .
A millisecond or one thousandth of a second is the time interval used in measuring flash characteristics . Time lag is the time that elapses between the closing of the electrical circuit and the peak of the flash . For most flashbulbs this is slightly less than 20 milliseconds , which is the same as .020 seconds ( 1/50 second ) . Flashbulbs are generally classified according to their time lag . The principle classes are the intermediate peak ( M - 2 , M - 3 , M - 25 and AG - 1 ) , the medium peak ( M ) , the slow peak ( S ) , and the very slow peak for focal plane shutters ( FP ) .
Flashcubes and AG - I Flashbulbs . These are midget lamps which reach maximum light output about 15 milliseconds after electrical contact is made . Both the flashcube and the AG - 1 flashbulb are quite small , and every effort has been made to reduce their size and weight . The AG - 1 , for example , has no base the wires which carry the current simply come out through a glass seal at the bottom of the bulb . Each flashcube is really four tiny flashbulbs in one . Each of the tiny flash units of the flashcube has its own highly polished reflector and four of them are sealed into a cube of clear plastic , so that there is a lamp for each of the four sides . The contact terminals are at the bottom of the cube .
The flashcube was designed primarily for use with small automatic cameras used by the novice , and the sockets built into the cameras are equipped with spring mechanisms which rotate the cube one - quarter turn automatically after each flash until all four flash units are fired . Flashcube adapters and complete flashguns are available , so that flashcubes may be used with conventional flashguns .
The high efficiency of the reflectors used with both the flashcubes and the AG - 1 flashbulbs compensates to a considerable degree for the low light output of these tiny lamps . Because of their relatively short peak interval or time lag , these flashbulbs can be used quite satisfactorily without synchronized shutters by setting the shutter to 1/25 or 1/30 second . This is explained more fully later in the Assignment .
Class M Flashbulbs . These are medium peak lamps , reaching maximum light output in 18 to 20 milliseconds after current is applied . The condition of the batteries has considerable influence on the time of peak - it may be as short as 16 milliseconds with absolutely fresh batteries of the proper type , or as long as 25 milliseconds if the batteries are run down . Therefore , it is important to keep flash batteries fresh at all times .
Class S Flashbulbs . These large lamps are used primarily for open flash work , so their time to peak brilliance is about 30 milliseconds after contact . They cannot be used with synchronized shutters because of their long time lag .
Class FP Flashbulbs . These lamps are designed for use with focal plane shutters . A focal plane shutter must move across the entire length of the film while making the exposure , even though its slit may be quite narrow . In the average 35mm camera , this takes about 20 milliseconds ( 1/50 second ) . The flash lamp must , therefore , give out a fairly uniform light throughout the time the shutter is moving , even though the actual exposure may be only 1/1000 second . If the light is not uniform for this 1/50 second , the exposure for one part of the film will not be the same as for others .
The FP type of flash lamps are made so that illumination rises to a maximum in from 15 to 20 milliseconds , holds constant at this level for another 20 milliseconds ( 40 for large lamps ) , and then dies out . This is shown in the timelight curves for the G - E No. 6 and No. 31 flashbulbs in Figure 1 .
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