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CHOOSING THE EXPOSURE
Getting the exposure right is probably one of the main concerns in photo- graphy , even though most modern 35mm SLRs are fully automated to deal with it . What makes an exposure ' right ' is actually a mixture of how you saw the original scene and the technical needs of the film . An essential first step in being able to control exposure is to understand the principles rather than to rely blindly on the camera's built - in meter . Automatic metering works wonder- fully most of the time , but when the lighting conditions are too unusual for it you should be able to take over yourself . To begin , there are three ways of measuring exposure , only one of which is used by a built - in camera meter :
REFLECTED LIGHT READINGS
These are readings of the amount of light reflected towards the camera from the subject . Under the same lighting , a dark surface reflects less light than a bright one . TTL camera metering works in this way , as does a handheld meter pointed towards the subject . For average - toned scenes ( and most are , by defin- ition ) , this type of reading works perfectly well . Difficulties arise when the subject is very dark , very light , backlit reflected readings tend to give settings that make blacks too light or whites too dark .
ABOVE Exactly the sort of high - contrast scene that could fool a camera's built - in light meter . Here , it might be wise to use a hand - held meter to take readings from the brightest and darkest areas of the subject , then calculate a compromise between them .
ABOVE Hand - held spot meters take accurate reflected light readings , and can be aimed optically at subjects .
Methods of using a hand - held meter include : ( 1 ) pointing the meter directly towards the subject to measure the light ; ( 2 ) taking readings from the brightest and darkest areas of a subject and making a compromise between them ; ( 3 ) aiming the meter at an 18 % grey card , which has average reflectance , as a substitute for the subject ; ( 4 ) using the meter to take an incident light reading of the light falling directly onto the subject .
INCIDENT LIGHT READINGS
The shortcomings of reflected readings are caused by differences in the subject , so that in theory , the most consistent readings should be of the light alone . Incident readings do just this , but need a handheld meter fitted with a cone or dome of translucent plastic over the sensor . This dome is held in the same position as the subject , facing toward the camera . In effect , the meter with its dome acts as an average subject . Because incident readings are not influenced by the subject or the background , they are ideal for tricky lighting situations . Most professionals carry one , and they are the normal method of measuring exposure in studio photography .
SUBSTITUTE READINGS
Reflected light readings that are not influenced by the brightness of the subject are possible , by substituting some other surface . The most accurate is a card that is toned a completely average grey . It reflects exactly 18 % of the light falling on it . Such grey cards can be bought at photographic stores . Two alternatives are white card readings ( from any completely white but not - too- shiny surface ) to which is added 2½ or 3 stops , and readings from your hand . This latter method depends on your knowing the difference in brightness between your skin and average grey .
BELOW RIGHT Scenes with a relatively limited contrast range can usually be handled perfectly adequately by the average camera's built - in light meter .
BELOW LEFT Reflected light readings are ideal in situations such as this , where the contrast varies from very dark to very bright . The readings are taken of the amount of light falling on the camera from the subject .
CHOOSING THE EXPOSURE
Getting the exposure right is probably one of the main concerns in photo- graphy , even though most modern 35mm SLRs are fully automated to deal with it . What makes an exposure ' right ' is actually a mixture of how you saw the original scene and the technical needs of the film . An essential first step in being able to control exposure is to understand the principles rather than to rely blindly on the camera's built - in meter . Automatic metering works wonder- fully most of the time , but when the lighting conditions are too unusual for it you should be able to take over yourself . To begin , there are three ways of measuring exposure , only one of which is used by a built - in camera meter :
REFLECTED LIGHT READINGS
These are readings of the amount of light reflected towards the camera from the subject . Under the same lighting , a dark surface reflects less light than a bright one . TTL camera metering works in this way , as does a handheld meter pointed towards the subject . For average - toned scenes ( and most are , by defin- ition ) , this type of reading works perfectly well . Difficulties arise when the subject is very dark , very light , backlit reflected readings tend to give settings that make blacks too light or whites too dark .
ABOVE Exactly the sort of high - contrast scene that could fool a camera's built - in light meter . Here , it might be wise to use a hand - held meter to take readings from the brightest and darkest areas of the subject , then calculate a compromise between them .
ABOVE Hand - held spot meters take accurate reflected light readings , and can be aimed optically at subjects .
Methods of using a hand - held meter include : ( 1 ) pointing the meter directly towards the subject to measure the light ; ( 2 ) taking readings from the brightest and darkest areas of a subject and making a compromise between them ; ( 3 ) aiming the meter at an 18 % grey card , which has average reflectance , as a substitute for the subject ; ( 4 ) using the meter to take an incident light reading of the light falling directly onto the subject .
INCIDENT LIGHT READINGS
The shortcomings of reflected readings are caused by differences in the subject , so that in theory , the most consistent readings should be of the light alone . Incident readings do just this , but need a handheld meter fitted with a cone or dome of translucent plastic over the sensor . This dome is held in the same position as the subject , facing toward the camera . In effect , the meter with its dome acts as an average subject . Because incident readings are not influenced by the subject or the background , they are ideal for tricky lighting situations . Most professionals carry one , and they are the normal method of measuring exposure in studio photography .
SUBSTITUTE READINGS
Reflected light readings that are not influenced by the brightness of the subject are possible , by substituting some other surface . The most accurate is a card that is toned a completely average grey . It reflects exactly 18 % of the light falling on it . Such grey cards can be bought at photographic stores . Two alternatives are white card readings ( from any completely white but not - too- shiny surface ) to which is added 2½ or 3 stops , and readings from your hand . This latter method depends on your knowing the difference in brightness between your skin and average grey .
BELOW RIGHT Scenes with a relatively limited contrast range can usually be handled perfectly adequately by the average camera's built - in light meter .
BELOW LEFT Reflected light readings are ideal in situations such as this , where the contrast varies from very dark to very bright . The readings are taken of the amount of light falling on the camera from the subject .
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