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الضوء الفلوريسنت .. مصدر الضوء .. كيفية التقاط وتطوير الصور الملونة
FLUORESCENT LIGHT
The most common type of artificial lighting , both outdoors and indoors , is now fluorescent . The major problem for the photographer is that these strip lights do not reproduce on film the way they appear to the eye . The reason for this lies in the way they work . Inside the glass envelope , an electrical discharge causes the gas to glow , and a fluorescent coating to the glass helps to make this look white . However , the spectrum of light that it emits has gaps , particularly in the red end of the spectrum . The result is that , while the effect is visually close to white , on film it looks green .
This would not be so bad if all fluorescent lamps were consistently green . However , there are different types , a variety of brands , and they change colour with age . The only two ways of making sure of exact correction are to use a colour meter or to make a test with several filters . For most people , neither of these alternatives is really acceptable , so the standard solution is to use one basic filter and hope for the best . All major filter manufacturers supply a fluorescent - correction filter , which is close to magenta with a strength equiva- lent to about CC30 on the Kodak Wratten scale . In fact , with a set of three gelatin Colour Compensating filters - CC10M , CC20M , and CC30M - you can bracket exposures and be reasonably certain of a close match . As fluorescent lights are deficient in red , daylight - balanced film is a better choice than Type B , which needs stronger filtration and so longer exposures .
For off - the - cuff shooting , a magenta filter over the lens is as much prepara- tion as you can make . If , however , you have more time to set up a shot , there are alternatives . One is to wrap magenta acetate sheets around the strip lights these are available from photographic dealers and suppliers of theatrical light- ing ) . Another is to aim a tungsten photographic lamp directly up into the ceiling where the fluorescent lamps are - the addition of orange light will help to overcome the green cast . A third possibility is to use portable flash - if you fit a magenta correction filter over the lens , and a CC30 green filter over the flash head , everything should balance .
BELOW A typical example of the sickly green cast that results from shooting with daylight - balanced film under
fluorescent lights . Unfortunately , the lights are not consistently green , but vary according to make and age .
LEFT Photographers wishing to use daylight - balanced film under tungsten lighting can avoid the green cast with the use of a simple filter , as shown here . Major filter manufacturers can supply a fluorescent - correction filter , which has a strength close to CC30 on the Kodak Wratten scale .
ABOVE Multi - coloured neon displays do not present the same problems as fluorescents , and can give rewarding results .
FLUORESCENT LIGHT
The most common type of artificial lighting , both outdoors and indoors , is now fluorescent . The major problem for the photographer is that these strip lights do not reproduce on film the way they appear to the eye . The reason for this lies in the way they work . Inside the glass envelope , an electrical discharge causes the gas to glow , and a fluorescent coating to the glass helps to make this look white . However , the spectrum of light that it emits has gaps , particularly in the red end of the spectrum . The result is that , while the effect is visually close to white , on film it looks green .
This would not be so bad if all fluorescent lamps were consistently green . However , there are different types , a variety of brands , and they change colour with age . The only two ways of making sure of exact correction are to use a colour meter or to make a test with several filters . For most people , neither of these alternatives is really acceptable , so the standard solution is to use one basic filter and hope for the best . All major filter manufacturers supply a fluorescent - correction filter , which is close to magenta with a strength equiva- lent to about CC30 on the Kodak Wratten scale . In fact , with a set of three gelatin Colour Compensating filters - CC10M , CC20M , and CC30M - you can bracket exposures and be reasonably certain of a close match . As fluorescent lights are deficient in red , daylight - balanced film is a better choice than Type B , which needs stronger filtration and so longer exposures .
For off - the - cuff shooting , a magenta filter over the lens is as much prepara- tion as you can make . If , however , you have more time to set up a shot , there are alternatives . One is to wrap magenta acetate sheets around the strip lights these are available from photographic dealers and suppliers of theatrical light- ing ) . Another is to aim a tungsten photographic lamp directly up into the ceiling where the fluorescent lamps are - the addition of orange light will help to overcome the green cast . A third possibility is to use portable flash - if you fit a magenta correction filter over the lens , and a CC30 green filter over the flash head , everything should balance .
BELOW A typical example of the sickly green cast that results from shooting with daylight - balanced film under
fluorescent lights . Unfortunately , the lights are not consistently green , but vary according to make and age .
LEFT Photographers wishing to use daylight - balanced film under tungsten lighting can avoid the green cast with the use of a simple filter , as shown here . Major filter manufacturers can supply a fluorescent - correction filter , which has a strength close to CC30 on the Kodak Wratten scale .
ABOVE Multi - coloured neon displays do not present the same problems as fluorescents , and can give rewarding results .
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