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درجة حرارة اللون .. مصدر الضوء .. كيفية التقاط وتطوير الصور الملونة
THE LIGHT SOURCE
COLOUR TEMPERATURE
Both daylight and tungsten lights have what is known as colour temperature . This is a measure of the bluishness or reddishness of light expressed in degrees of temperature ( Kelvins , which are similar to centigrade , but begin at absolute zero ) . Bluish light , as from a clear sky , has a high colour temperature ; reddish light , like that from a low - wattage lamp , has a low colour temperature . Noon sunlight , for which daylight - balanced film is calibrated , is 5500K .
What makes colour temperature critical in photography , particularly indoors and in open shade outside , is that the eye quickly adjusts to differences . Film simply records what is there . The table shows the range of normal conditions , from candlelight to a deep blue sky . In ordinary pictorial photography , there are often no adjustments needed : a reddish sunset is expected and normal . On occasion , however , the colour cast can look inappropriate , such as a portrait taken under a blue sky in the shade of a building ( the result will be too blue ) . Then , the answer is to use light - balancing filters over the lens , and in extreme cases of red / orange lighting , to switch to Type B film .
Calculations are often more convenient to make in the form of mireds ( micro reciprocal degrees ) . These are the equivalent of one million divided by the Kelvin number , and are easier to use because they can be added and subtracted but stay constant . The table shows how they relate to filters , each of which has a mired shift value . Bluish filters ( Kodak's 80 and 82 series ) raise colour temperature and have negative mired values ; straw- and orange - tinted filters lower the colour temperature and have positive mired shift values . For instance , if you were using Type B film , balanced for 3200K ( 312 mireds ) , but shooting by the light of a domestic lamp that gave 2900K ( 344 mireds ) , the way to correct the effect would be to use a filter with a value of minus 32 mireds - in other words , a Kodak 82B or equivalent from another manufacturer .
Outdoors , the combination of a midday sun and some surrounding blue sky gives about 5500K , for which daylight film is balanced , and which appears ' white ' . Earlier and later in the day , the sun is lower and some of its shorter , bluer wavelengths are scattered by the atmosphere , making it more yellowish , orange and sometimes even red . Out of the sun , a blue sky has a much higher colour temperature , 10,000K and higher . Clouds , if continuous , usually raise the colour temperature slightly , perhaps to about 6000K , which is why a slightly warm - tinted filter , such as an 81B , can be useful .
Indoors , tungsten lamps have more predictable colour temperatures , as the table shows . Judging the colour temperature is difficult at first , but it is usually enough to know the approximate values .
Mired shift values for Kodak filters
THE LIGHT SOURCE
COLOUR TEMPERATURE
Both daylight and tungsten lights have what is known as colour temperature . This is a measure of the bluishness or reddishness of light expressed in degrees of temperature ( Kelvins , which are similar to centigrade , but begin at absolute zero ) . Bluish light , as from a clear sky , has a high colour temperature ; reddish light , like that from a low - wattage lamp , has a low colour temperature . Noon sunlight , for which daylight - balanced film is calibrated , is 5500K .
What makes colour temperature critical in photography , particularly indoors and in open shade outside , is that the eye quickly adjusts to differences . Film simply records what is there . The table shows the range of normal conditions , from candlelight to a deep blue sky . In ordinary pictorial photography , there are often no adjustments needed : a reddish sunset is expected and normal . On occasion , however , the colour cast can look inappropriate , such as a portrait taken under a blue sky in the shade of a building ( the result will be too blue ) . Then , the answer is to use light - balancing filters over the lens , and in extreme cases of red / orange lighting , to switch to Type B film .
Calculations are often more convenient to make in the form of mireds ( micro reciprocal degrees ) . These are the equivalent of one million divided by the Kelvin number , and are easier to use because they can be added and subtracted but stay constant . The table shows how they relate to filters , each of which has a mired shift value . Bluish filters ( Kodak's 80 and 82 series ) raise colour temperature and have negative mired values ; straw- and orange - tinted filters lower the colour temperature and have positive mired shift values . For instance , if you were using Type B film , balanced for 3200K ( 312 mireds ) , but shooting by the light of a domestic lamp that gave 2900K ( 344 mireds ) , the way to correct the effect would be to use a filter with a value of minus 32 mireds - in other words , a Kodak 82B or equivalent from another manufacturer .
Outdoors , the combination of a midday sun and some surrounding blue sky gives about 5500K , for which daylight film is balanced , and which appears ' white ' . Earlier and later in the day , the sun is lower and some of its shorter , bluer wavelengths are scattered by the atmosphere , making it more yellowish , orange and sometimes even red . Out of the sun , a blue sky has a much higher colour temperature , 10,000K and higher . Clouds , if continuous , usually raise the colour temperature slightly , perhaps to about 6000K , which is why a slightly warm - tinted filter , such as an 81B , can be useful .
Indoors , tungsten lamps have more predictable colour temperatures , as the table shows . Judging the colour temperature is difficult at first , but it is usually enough to know the approximate values .
Mired shift values for Kodak filters
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