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اختيار علامة التعريض .. مصدر الضوء .. كيفية التقاط وتطوير الصور بالأبيض والأسود
SIGN CHOOSING THE EXPOSURE
There are three basic methods of measuring light and exposure , although only two are possible with a camera's through - the - lens meter . They are : reflec- ted light readings , incident light readings , and substitute readings . Each has its advantages in certain conditions . Incident light readings can only be made with a hand - held meter fitted with a specially diffused receptor , but they are so valuable in some situations that most serious photographers carry one .
REFLECTED LIGHT READINGS
These can be made either with the camera's through - the - lens system or a hand- held meter pointed directly at the scene . The meter measures the light reflec- ted from surfaces , and so a combination of the intensity of the light itself and the inherent darkness or brightness of objects . It is ideal for uncomplicated lighting conditions in which there are no really great differences in tone across the image . However , if there are strong shadows and bright highlights , an average reflected light reading may not give an accurate exposure for what is important in the picture . Instead , it is normal to take two readings , one from a shadow and the other from a bright area , and set the exposure halfway be- tween . For such two - part readings , a spotmeter is very useful ; with the camera's built - in meter , you should either approach the subject more closely to make the reading , or change temporarily to a longer focus lens .
Another alternative , useful if the important part of the picture is very small and either brighter or darker than its surroundings , is to limit the area that you measure . Here again , use a spotmeter , move closer , or switch to a lens with a narrower angle of view .
INCIDENT LIGHT READINGS
The second method of measuring exposure is to ignore how bright or dark the subject is , and record only the strength of the light falling on it . This is the principle of the incident light reading , which is made with a hand - held meter that has a milky white plastic dome fitted over the light sensor ( this is removable so that the meter can be used for incident or reflected light readings ) .
The technique is to hold the meter in the same position as the subject - or at least in the same lighting , if the subject is not conveniently accessible - pointing the receptor towards the camera . The great value of this method is that the setting is not confused by dark or light subjects .
SUBSTITUTE READINGS
By measuring the light reflected from a surface that you are already familiar with , you can make reflected light readings that are not influenced by the subject . The most accurate substitute is an average grey , and a card made for this purpose can be bought from photo dealers .
Taking Readings
The four basic methods of using a hand - held meter :
1. With the reflected - light method , the meter is pointed directly towards the subject to measure the light .
2. With contrasty subjects , it is a good idea to take readings from the brightest and darkest areas of the subject and then make a compromise between them .
3. An 18 % gray card , which has average reflectance , can be used as a substitute for the subject .
4. An incident - light reading measures only the light falling on the subject . A translucent plastic cover is fitted to the meter .
BELOW Grey scales are commonly used to take substitute readings , whereby a measurement is taken of light being reflected from a surface that you are familiar with . The reflected light reading is not , therefore , influenced by the subject .
Shading the Meter
When using a hand - held meter outdoors , shade the meter with your hand so that the reading is not overly influenced by the sky .
TOP LEFT High contrast subjects may require a modification to the standard reflected light reading technique . Instead of a single reading , two should be taken , one from the highlights , and one from the shadow . The correct exposure should fall half - way between .
LEFT Unlike the above example low contrast scenes usually only need a single reflected light reading . This can be done either with a hand - held meter pointed directly at the scene , or with the camera's TTL light meter .
SIGN CHOOSING THE EXPOSURE
There are three basic methods of measuring light and exposure , although only two are possible with a camera's through - the - lens meter . They are : reflec- ted light readings , incident light readings , and substitute readings . Each has its advantages in certain conditions . Incident light readings can only be made with a hand - held meter fitted with a specially diffused receptor , but they are so valuable in some situations that most serious photographers carry one .
REFLECTED LIGHT READINGS
These can be made either with the camera's through - the - lens system or a hand- held meter pointed directly at the scene . The meter measures the light reflec- ted from surfaces , and so a combination of the intensity of the light itself and the inherent darkness or brightness of objects . It is ideal for uncomplicated lighting conditions in which there are no really great differences in tone across the image . However , if there are strong shadows and bright highlights , an average reflected light reading may not give an accurate exposure for what is important in the picture . Instead , it is normal to take two readings , one from a shadow and the other from a bright area , and set the exposure halfway be- tween . For such two - part readings , a spotmeter is very useful ; with the camera's built - in meter , you should either approach the subject more closely to make the reading , or change temporarily to a longer focus lens .
Another alternative , useful if the important part of the picture is very small and either brighter or darker than its surroundings , is to limit the area that you measure . Here again , use a spotmeter , move closer , or switch to a lens with a narrower angle of view .
INCIDENT LIGHT READINGS
The second method of measuring exposure is to ignore how bright or dark the subject is , and record only the strength of the light falling on it . This is the principle of the incident light reading , which is made with a hand - held meter that has a milky white plastic dome fitted over the light sensor ( this is removable so that the meter can be used for incident or reflected light readings ) .
The technique is to hold the meter in the same position as the subject - or at least in the same lighting , if the subject is not conveniently accessible - pointing the receptor towards the camera . The great value of this method is that the setting is not confused by dark or light subjects .
SUBSTITUTE READINGS
By measuring the light reflected from a surface that you are already familiar with , you can make reflected light readings that are not influenced by the subject . The most accurate substitute is an average grey , and a card made for this purpose can be bought from photo dealers .
Taking Readings
The four basic methods of using a hand - held meter :
1. With the reflected - light method , the meter is pointed directly towards the subject to measure the light .
2. With contrasty subjects , it is a good idea to take readings from the brightest and darkest areas of the subject and then make a compromise between them .
3. An 18 % gray card , which has average reflectance , can be used as a substitute for the subject .
4. An incident - light reading measures only the light falling on the subject . A translucent plastic cover is fitted to the meter .
BELOW Grey scales are commonly used to take substitute readings , whereby a measurement is taken of light being reflected from a surface that you are familiar with . The reflected light reading is not , therefore , influenced by the subject .
Shading the Meter
When using a hand - held meter outdoors , shade the meter with your hand so that the reading is not overly influenced by the sky .
TOP LEFT High contrast subjects may require a modification to the standard reflected light reading technique . Instead of a single reading , two should be taken , one from the highlights , and one from the shadow . The correct exposure should fall half - way between .
LEFT Unlike the above example low contrast scenes usually only need a single reflected light reading . This can be done either with a hand - held meter pointed directly at the scene , or with the camera's TTL light meter .
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