تويت
التصوير الفوتوغرافي الحديث
التصوير بالألوان وحقائق حول المرشحات
الجزء الأول التصوير بالألوان
توازن اللون
COLOR BALANCE
COLOR FILMS
Let us assume , for the moment , that daylight is composed of exactly equal proportions of blue , green , and red light . A perfectly white object would then reflect equal amounts of blue , green and red light . To reproduce this object accurately with color film , the three emulsion layers must be carefully balanced . so that all three have equal sensitivity . They will then produce three equally dense color images in the three color layers , which will add up to the original , perfect white .
Now let us see what happens if we use this same film to photograph this same object under indoor tungsten illumination . Tungsten illumination has proportionally more red and less blue than daylight . The white object will , therefore , reflect more red than blue . This will cause it to photograph as a warm white , tending toward orange or red . The object appeared white to us because our eyes had accommodated to the color balance of tungsten illumination . The photograph will , therefore , appear off - color , even though it is actually an accurate reproduction of the original color ..
To photograph our white object so that it will be reproduced as white under tungsten illumination can be done by increasing the sensitivity of the blue - sensitive emulsion ( or reducing the sensitivity of the red - sensitive emulsion ) . With a film so balanced , even though there is actually more red light present , the more sensitive blue - sensitive emulsion will compensate for it and restore the balance to produce a true white . The film will now photograph colors without the orange tint under tungsten illumination . However , if this film were to be used in blue - rich daylight , the increased blue sensitivity would result in an overall bluish cast to everything in the photograph .
From the foregoing explanation , we can see that if we want to photograph objects in their true colors , the three emulsions of the film must be carefully balanced for use with the light under which the photograph is to be made .
Even a casual glance at Table II , page 20 , shows you that the color of so - called white light can vary through a tremendous range from the yellow of a candle flame to the blue of a northern sky . It is impossible to provide color films that exactly match this wide range . However , film manufacturers have standardized on three different color balances which take care of most situations quite well : Daylight , Type A tungsten , and Type B tungsten films .
DAYLIGHT FILM . Daylight type film is balanced for a color temperature of 6000 ° K. This is the color of average noon daylight in the northern hemisphere when the sun is shining brightly and there are a few white clouds in the sky . When . the sun is low on the horizon , either early in the morning or late in the afternoon , daylight is noticeably warmer ( more red ) . Its color temperature may drop to 5000 ° K . Pictures taken with daylight type film under such lighting have a pronounced orange or reddish cast .
TYPE A TUNGSTEN FILM . Type A tungsten film is balanced for a color temperature of 3400 ° K. This is the light given off by photoflood lamps . Such lamps were once used almost exclusively for indoor color photography , particularly by the amateur , because they produced more light per watt of electricity than any other type of light easily available . They could , therefore , be used in homes where electrical power was limited . Type A tungsten film is now used almost exclusively for 8mm and 16mm motion picture photography .
TYPE B TUNGSTEN FILM . Type B tungsten film is balanced for a color temperature of 3200 ° K. Photoflood lamps are generally very efficient , but they have off - setting disadvantages . At 3400 ° K. they are operated at very near temperature at which tungsten boils . As a result , photoflood lamps are very short - lived from two hours in the smaller sizes to four hours in the larger . Furthermore , the color temperature changes noticeably after only a short period of use . Accordingly , lamp manufacturers have developed a new type of lamp which operates at 3200 ° K. as compared to 3400 ° K. for the photoflood . At this lower temperature the lamps are more uniform in color throughout their life and have a longer life as well . These lamps are called 3200⁰ lamps . Type B tungsten film is color - balanced to match their light .
One very important source of light employed extensively by photographers is flash . Electronic flash generally produces light having a color temperature of 6000⁰ 6500 ° K. , which is substantially the same as daylight . Electronic flash can , therefore , be used with daylight type color films without a color compensating filter , and the resulting color will be quite satisfactory for all but very critical work
The material in an expendable flash bulb emits light at a color temperature of 3800 ° K. when ignited . Flash lamps are , therefore , coated with a blue dye which acts as a color filter , and the resulting light has a temperature of 6000⁰ K. Blue flash bulbs are suitable for use with daylight type color films .
NEGATIVE COLOR FILMS . Negative color films are generally not supplied with differing color balances . From the manufacturer's point of view , it is much more economical to supply this film with only one color balance and then adjust the color of the final print during process of printing by means of a suitable filter . This , of course , is of advantage to the photographer also , since he need stock only one film for use in either daylight or artificial light .
التصوير بالألوان وحقائق حول المرشحات
الجزء الأول التصوير بالألوان
توازن اللون
COLOR BALANCE
COLOR FILMS
Let us assume , for the moment , that daylight is composed of exactly equal proportions of blue , green , and red light . A perfectly white object would then reflect equal amounts of blue , green and red light . To reproduce this object accurately with color film , the three emulsion layers must be carefully balanced . so that all three have equal sensitivity . They will then produce three equally dense color images in the three color layers , which will add up to the original , perfect white .
Now let us see what happens if we use this same film to photograph this same object under indoor tungsten illumination . Tungsten illumination has proportionally more red and less blue than daylight . The white object will , therefore , reflect more red than blue . This will cause it to photograph as a warm white , tending toward orange or red . The object appeared white to us because our eyes had accommodated to the color balance of tungsten illumination . The photograph will , therefore , appear off - color , even though it is actually an accurate reproduction of the original color ..
To photograph our white object so that it will be reproduced as white under tungsten illumination can be done by increasing the sensitivity of the blue - sensitive emulsion ( or reducing the sensitivity of the red - sensitive emulsion ) . With a film so balanced , even though there is actually more red light present , the more sensitive blue - sensitive emulsion will compensate for it and restore the balance to produce a true white . The film will now photograph colors without the orange tint under tungsten illumination . However , if this film were to be used in blue - rich daylight , the increased blue sensitivity would result in an overall bluish cast to everything in the photograph .
From the foregoing explanation , we can see that if we want to photograph objects in their true colors , the three emulsions of the film must be carefully balanced for use with the light under which the photograph is to be made .
Even a casual glance at Table II , page 20 , shows you that the color of so - called white light can vary through a tremendous range from the yellow of a candle flame to the blue of a northern sky . It is impossible to provide color films that exactly match this wide range . However , film manufacturers have standardized on three different color balances which take care of most situations quite well : Daylight , Type A tungsten , and Type B tungsten films .
DAYLIGHT FILM . Daylight type film is balanced for a color temperature of 6000 ° K. This is the color of average noon daylight in the northern hemisphere when the sun is shining brightly and there are a few white clouds in the sky . When . the sun is low on the horizon , either early in the morning or late in the afternoon , daylight is noticeably warmer ( more red ) . Its color temperature may drop to 5000 ° K . Pictures taken with daylight type film under such lighting have a pronounced orange or reddish cast .
TYPE A TUNGSTEN FILM . Type A tungsten film is balanced for a color temperature of 3400 ° K. This is the light given off by photoflood lamps . Such lamps were once used almost exclusively for indoor color photography , particularly by the amateur , because they produced more light per watt of electricity than any other type of light easily available . They could , therefore , be used in homes where electrical power was limited . Type A tungsten film is now used almost exclusively for 8mm and 16mm motion picture photography .
TYPE B TUNGSTEN FILM . Type B tungsten film is balanced for a color temperature of 3200 ° K. Photoflood lamps are generally very efficient , but they have off - setting disadvantages . At 3400 ° K. they are operated at very near temperature at which tungsten boils . As a result , photoflood lamps are very short - lived from two hours in the smaller sizes to four hours in the larger . Furthermore , the color temperature changes noticeably after only a short period of use . Accordingly , lamp manufacturers have developed a new type of lamp which operates at 3200 ° K. as compared to 3400 ° K. for the photoflood . At this lower temperature the lamps are more uniform in color throughout their life and have a longer life as well . These lamps are called 3200⁰ lamps . Type B tungsten film is color - balanced to match their light .
One very important source of light employed extensively by photographers is flash . Electronic flash generally produces light having a color temperature of 6000⁰ 6500 ° K. , which is substantially the same as daylight . Electronic flash can , therefore , be used with daylight type color films without a color compensating filter , and the resulting color will be quite satisfactory for all but very critical work
The material in an expendable flash bulb emits light at a color temperature of 3800 ° K. when ignited . Flash lamps are , therefore , coated with a blue dye which acts as a color filter , and the resulting light has a temperature of 6000⁰ K. Blue flash bulbs are suitable for use with daylight type color films .
NEGATIVE COLOR FILMS . Negative color films are generally not supplied with differing color balances . From the manufacturer's point of view , it is much more economical to supply this film with only one color balance and then adjust the color of the final print during process of printing by means of a suitable filter . This , of course , is of advantage to the photographer also , since he need stock only one film for use in either daylight or artificial light .
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