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موازنة مصدر الضوء والفيلم .. التصوير الملون .. المرشد خطوة بخطوة للتصوير الفوتوغرافي
Balancing light source and film
What we call " white light " is really a mix- ture of wavelengths containing all the colors of the spectrum . This mixture varies accord- ing to the light source . For example , candle- light contains more red than blue wave- lengths , giving it a slightly warm color . In shadow areas on a clear day , where the only light is scattered from blue sky , the light is bluish . These differences in the compon- ents of white light are sometimes ex- pressed in temperatures on a scale measured in Kelvins ( K ) , see below . The temperature of each color corresponds to the temperature of a hypothetical black body when heated to emit that color light . As the body grows hotter , it glows red , then through orange and yellow to blue ; so the reddish light cast by an ordinary household lamp is lower on the scale than the more bluish light of sun- light at midday .
Most of the light sources used for photo- graphy are shown below . The 500 watt tungsten lamps used in most photolamps and spotlights have a color temperature of 3200K . Photofloods are short - life over - run lamps , which give a slightly bluer light and have a color temperature of 3400K . In practice , sunlight is often mixed with bluer sky light so that typical " photographic day- light " is at least 5400K . Noon sunlight , blue tinted flashbulbs , and electronic flash are fairly similar in color temperature .
Color correction filters
Color slide films will render true colors only in light of a specified color temperature . The two main types of slide film are " tungsten " ( 3200K ) and “ daylight " ( 5500K ) . The pictures below show you how , by fitting the appropriate correction filter over the lens and making the recommended compensa- tion in exposure , you can use both types of film in other lighting ( the filter numbers refer to Kodak filters ) . In fluorescent lighting use daylight film for " cold white " ( bluish ) tubes , and tungsten light film with a 40R correc- tion filter for " warm white " types . Color negatives can be color balanced in printing .
Color temperature and correcting filters
1800K Candlelight
2800K Household light
3200K Photolamps
Photoflood 3400K
5400K Sunlight
6000K Flash
12000K Blue sky light
Daylight film suits a mixture of sunlight plus light reflected from the sky , as in the picture above . Correcting filters must be used in lighting of lower color tempera- ture , such as household light , far left , and photographic lighting , left : or of a higher color temperature such as blue sky light , right .
Tungsten light film
Tungsten film is balanced for scenes lit by photographic lamps , such as above . Correcting filters must be used in higher color temperature lighting , such as daylight , right , and blue sky light , far right ; and in lower color temperature light- ing , such as household light , left .
Mixed light sources
The scene below was lit by two different light sources - 100 watt lamps and daylight . Because it was taken on daylight film , correct color has recorded only in the area lit by natural light the foreground . Tungsten film would reproduce . the background color correctly . but would tint other areas blue .
Where mixed light is unavoid- able you may be able to part - filter the image to correct for the mis- matched light . In studio work you can put the appropriate filter over the light source .
Color and daylight
The color temperature of daylight varies enormously according to weather conditions and time of day . Most photographers do not try to filter the light in every scene so that it appears neutral . The dawn scene , right , was taken un- filtered on daylight film and repro- duces the subject as it appeared at the time . However , with another subject , such as a portrait , the pink cast created by the light may well be unacceptable .
Other useful filters
The colored filters used in black and white photography cannot play the same role in color photo- graphy . Two apparently colorless filters are more useful ultra- violet and polarizing filters .
Ultra - violet filters
An ultra - violet ( UV ) absorbing filter removes ultra - violet light which . although invisible to the eye , re- cords as a blue cast on color film . This occurs most noticeably in dis- tant landscapes at high altitudes , and in seascapes . You can there- fore choose to include the blue haze , near right , or , by using this filter to absorb ultra - violet light . record the scene as it actually appeared to the eye , far right .
Polarizing filter
Some of the light from a blue sky is polarized ( see p . 101 ) , particu- larly in sky areas at right angles to the sun's rays . This reduces the intensity of color recorded , near right . A gray . polarizing filter can remove polarized light rays with- out distorting other colors , if posi- tioned correctly . By rotating the filter on the lens you can , for ex- ample , deepen the blue of a sky , far right , or reduce glare - polar- ized light reflected from glass , water or polished non - metal surfaces .
Balancing light source and film
What we call " white light " is really a mix- ture of wavelengths containing all the colors of the spectrum . This mixture varies accord- ing to the light source . For example , candle- light contains more red than blue wave- lengths , giving it a slightly warm color . In shadow areas on a clear day , where the only light is scattered from blue sky , the light is bluish . These differences in the compon- ents of white light are sometimes ex- pressed in temperatures on a scale measured in Kelvins ( K ) , see below . The temperature of each color corresponds to the temperature of a hypothetical black body when heated to emit that color light . As the body grows hotter , it glows red , then through orange and yellow to blue ; so the reddish light cast by an ordinary household lamp is lower on the scale than the more bluish light of sun- light at midday .
Most of the light sources used for photo- graphy are shown below . The 500 watt tungsten lamps used in most photolamps and spotlights have a color temperature of 3200K . Photofloods are short - life over - run lamps , which give a slightly bluer light and have a color temperature of 3400K . In practice , sunlight is often mixed with bluer sky light so that typical " photographic day- light " is at least 5400K . Noon sunlight , blue tinted flashbulbs , and electronic flash are fairly similar in color temperature .
Color correction filters
Color slide films will render true colors only in light of a specified color temperature . The two main types of slide film are " tungsten " ( 3200K ) and “ daylight " ( 5500K ) . The pictures below show you how , by fitting the appropriate correction filter over the lens and making the recommended compensa- tion in exposure , you can use both types of film in other lighting ( the filter numbers refer to Kodak filters ) . In fluorescent lighting use daylight film for " cold white " ( bluish ) tubes , and tungsten light film with a 40R correc- tion filter for " warm white " types . Color negatives can be color balanced in printing .
Color temperature and correcting filters
1800K Candlelight
2800K Household light
3200K Photolamps
Photoflood 3400K
5400K Sunlight
6000K Flash
12000K Blue sky light
Daylight film suits a mixture of sunlight plus light reflected from the sky , as in the picture above . Correcting filters must be used in lighting of lower color tempera- ture , such as household light , far left , and photographic lighting , left : or of a higher color temperature such as blue sky light , right .
Tungsten light film
Tungsten film is balanced for scenes lit by photographic lamps , such as above . Correcting filters must be used in higher color temperature lighting , such as daylight , right , and blue sky light , far right ; and in lower color temperature light- ing , such as household light , left .
Mixed light sources
The scene below was lit by two different light sources - 100 watt lamps and daylight . Because it was taken on daylight film , correct color has recorded only in the area lit by natural light the foreground . Tungsten film would reproduce . the background color correctly . but would tint other areas blue .
Where mixed light is unavoid- able you may be able to part - filter the image to correct for the mis- matched light . In studio work you can put the appropriate filter over the light source .
Color and daylight
The color temperature of daylight varies enormously according to weather conditions and time of day . Most photographers do not try to filter the light in every scene so that it appears neutral . The dawn scene , right , was taken un- filtered on daylight film and repro- duces the subject as it appeared at the time . However , with another subject , such as a portrait , the pink cast created by the light may well be unacceptable .
Other useful filters
The colored filters used in black and white photography cannot play the same role in color photo- graphy . Two apparently colorless filters are more useful ultra- violet and polarizing filters .
Ultra - violet filters
An ultra - violet ( UV ) absorbing filter removes ultra - violet light which . although invisible to the eye , re- cords as a blue cast on color film . This occurs most noticeably in dis- tant landscapes at high altitudes , and in seascapes . You can there- fore choose to include the blue haze , near right , or , by using this filter to absorb ultra - violet light . record the scene as it actually appeared to the eye , far right .
Polarizing filter
Some of the light from a blue sky is polarized ( see p . 101 ) , particu- larly in sky areas at right angles to the sun's rays . This reduces the intensity of color recorded , near right . A gray . polarizing filter can remove polarized light rays with- out distorting other colors , if posi- tioned correctly . By rotating the filter on the lens you can , for ex- ample , deepen the blue of a sky , far right , or reduce glare - polar- ized light reflected from glass , water or polished non - metal surfaces .
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