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الإضاءة المنخفضة .. معدات وتقنيات إضافية .. المرشد خطوة بخطوة للتصوير الفوتوغرافي
Low lighting
If you intend to take many pictures indoors or after dark using available light you should use lenses that have a wide maximum aper- ture . A lens with a maximum aperture of f2 will allow you to take hand - held pictures in half the light possible with an f2.8 lens .
In dim lighting a light meter sensitive enough to give reliable readings is essential . Selenium cell meters are comparatively insensitive in poor light . Battery powered hand and built - in meters with CdS , silicon or similar cells ( see p . 39 ) are much more responsive . If lighting conditions are very low , you can use a white card reading to get a response from the meter , as shown on page 104. Alternatively , set the ASA dial to twice or four times the correct rating for the film to get a meter reading . Then multiply the reading by this amount .
Long exposure times create problems of camera shake and reciprocity failure , as ex- plained on the opposite page . To avoid these , you can use supplementary lighting , dis- cussed on pages 108-13 .
Low intensity , soft lighting
Subjects with low , soft lighting , such as shown left , are not difficult to expose for if you have an accur- ate light meter . The exposure read- ing suggested was 1/30 sec at f2 on fast , 1200 ASA film . But to : avoid camera shake it was exposed at 1/60 sec , and the film given longer development . Because the lighting was soft the overdeveloped negative still printed well on nor- mal grade paper .
Low intensity , harsh lighting
Low intensity , harsh light created by a dark - toned interior , and bril- liant daylight outside a window presents a difficult exposure problem . It was solved in the picture , below . by losing the detail through the window . The exposure was mea- sured by averaging only the light and dark areas within the room . The 400 ASA film was overexposed by one stop , then given reduced development to decrease the contrast .
Contrasty lighting
Low light level subjects such as room interiors , bars , or street scenes at night are usually contrasty as well as dim . The lighting is much more uneven than day- light . As a result contrast is more of a problem than dimness . The more exposure you give to bring out shadow detail , the more " burned out " the lightest areas become . " Uprating " the film , by under- exposing and overdeveloping ( see pp . 126- 7 ) , which has advantages for dim lighting . increases the contrast still further . It is better to choose a viewpoint from which the subject is as softly and evenly lit as possible . rather than just brightly lit. To do this , make use of any supplementary lighting from signs , reflective surfaces , or open doorways . The flatter the lighting the more you can overdevelop fast film - up to 3000 ASA or beyond and still avoid producing unac- ceptably hard negatives .
If you are using flash lighting you can reduce contrast by firing the flash several times during a long exposure ( see p . 113 ) .
Contrast and distance
When photographing someone in- doors it is tempting to place them near the window . This does in- crease the light but often gives very harsh contrast , as shown near right . By moving the subject away from the window and toward the oppo- site wall the contrast is reduced , as shown far right . Light from the window is weaker and reflected light from surroundings such as the rear wall is increased . The exposure must be increased to compensate for the reduced light .
Weak , uneven illumination
Under weak , uneven light you will often have to use a very long ex- posure . One way of reducing the contrast is to spread the illumi- nation . Indoors you can do this by using light - toned reflectors pos- itioned around the subject . Or , if you are working under normal room lighting , you can swing the light , during exposure , to spread the illumination . If the lamp is included in the picture its path will record as white trails . Outdoors at night you can use street lamps or the light cast by passing automobiles to illuminate a scene . The long ex- posure will record moving lights as bright lines , such as shown right , which can form interesting patterns in themselves .
Reciprocity failure
If you give extremely brief or long exposures most films behave as if they have a slower speed rating and give altered contrast . This is called reciprocity failure . It means that you must give extra exposure when working at speeds of faster than 1/1000 sec or longer than sec . The easiest way to do this is by opening the aperture , as a longer exposure will simply increase the reciprocity failure .
In practice you will hardly notice
any effect on black and white film with exposure times of up to 2-3 seconds . Color films show a notice- able color change at slow speeds .
The table below shows by how much you should open the aper- ture to compensate for reciprocity failure with normal black and white film . The development time should also be adjusted as shown below . to reduce the contrast . Long expo- sures increase contrast and require a shorter development .
Candlelight
A solitary candle gives very hard . contrasty lighting . But in the pic- ture above , the random grouping of candles has created a softer , almost floodlit effect . The high contrast was reduced by the reflec- live white table cloth and slight flame movement during the 4 sec- ond exposure . The light reading was measured from the faces to record them correctly . Notice how the figures were arranged so that they could hold their positions comfortably during the exposure .
The aperture suggested by the meter reading was increased and the development time of the film reduced to avoid reciprocity failure with the long exposure .
Assignment : measuring exposure
Photograph part of a room interior from a viewpoint which includes a window . Use the camera on a tripod . By means of the most appropriate reading technique take the following pictures :
A. One taken during daylight hours ( harsh sunlight should not be shining directly into the room ) . This picture must show maximum detail within the room .
B. One picture under the same lighting conditions but including detail both inside and outside the room .
C. A picture taken after dark using existing room lighting only .
Compare the appearance of the room in each picture and check your exposure accuracy .
Low lighting
If you intend to take many pictures indoors or after dark using available light you should use lenses that have a wide maximum aper- ture . A lens with a maximum aperture of f2 will allow you to take hand - held pictures in half the light possible with an f2.8 lens .
In dim lighting a light meter sensitive enough to give reliable readings is essential . Selenium cell meters are comparatively insensitive in poor light . Battery powered hand and built - in meters with CdS , silicon or similar cells ( see p . 39 ) are much more responsive . If lighting conditions are very low , you can use a white card reading to get a response from the meter , as shown on page 104. Alternatively , set the ASA dial to twice or four times the correct rating for the film to get a meter reading . Then multiply the reading by this amount .
Long exposure times create problems of camera shake and reciprocity failure , as ex- plained on the opposite page . To avoid these , you can use supplementary lighting , dis- cussed on pages 108-13 .
Low intensity , soft lighting
Subjects with low , soft lighting , such as shown left , are not difficult to expose for if you have an accur- ate light meter . The exposure read- ing suggested was 1/30 sec at f2 on fast , 1200 ASA film . But to : avoid camera shake it was exposed at 1/60 sec , and the film given longer development . Because the lighting was soft the overdeveloped negative still printed well on nor- mal grade paper .
Low intensity , harsh lighting
Low intensity , harsh light created by a dark - toned interior , and bril- liant daylight outside a window presents a difficult exposure problem . It was solved in the picture , below . by losing the detail through the window . The exposure was mea- sured by averaging only the light and dark areas within the room . The 400 ASA film was overexposed by one stop , then given reduced development to decrease the contrast .
Contrasty lighting
Low light level subjects such as room interiors , bars , or street scenes at night are usually contrasty as well as dim . The lighting is much more uneven than day- light . As a result contrast is more of a problem than dimness . The more exposure you give to bring out shadow detail , the more " burned out " the lightest areas become . " Uprating " the film , by under- exposing and overdeveloping ( see pp . 126- 7 ) , which has advantages for dim lighting . increases the contrast still further . It is better to choose a viewpoint from which the subject is as softly and evenly lit as possible . rather than just brightly lit. To do this , make use of any supplementary lighting from signs , reflective surfaces , or open doorways . The flatter the lighting the more you can overdevelop fast film - up to 3000 ASA or beyond and still avoid producing unac- ceptably hard negatives .
If you are using flash lighting you can reduce contrast by firing the flash several times during a long exposure ( see p . 113 ) .
Contrast and distance
When photographing someone in- doors it is tempting to place them near the window . This does in- crease the light but often gives very harsh contrast , as shown near right . By moving the subject away from the window and toward the oppo- site wall the contrast is reduced , as shown far right . Light from the window is weaker and reflected light from surroundings such as the rear wall is increased . The exposure must be increased to compensate for the reduced light .
Weak , uneven illumination
Under weak , uneven light you will often have to use a very long ex- posure . One way of reducing the contrast is to spread the illumi- nation . Indoors you can do this by using light - toned reflectors pos- itioned around the subject . Or , if you are working under normal room lighting , you can swing the light , during exposure , to spread the illumination . If the lamp is included in the picture its path will record as white trails . Outdoors at night you can use street lamps or the light cast by passing automobiles to illuminate a scene . The long ex- posure will record moving lights as bright lines , such as shown right , which can form interesting patterns in themselves .
Reciprocity failure
If you give extremely brief or long exposures most films behave as if they have a slower speed rating and give altered contrast . This is called reciprocity failure . It means that you must give extra exposure when working at speeds of faster than 1/1000 sec or longer than sec . The easiest way to do this is by opening the aperture , as a longer exposure will simply increase the reciprocity failure .
In practice you will hardly notice
any effect on black and white film with exposure times of up to 2-3 seconds . Color films show a notice- able color change at slow speeds .
The table below shows by how much you should open the aper- ture to compensate for reciprocity failure with normal black and white film . The development time should also be adjusted as shown below . to reduce the contrast . Long expo- sures increase contrast and require a shorter development .
Candlelight
A solitary candle gives very hard . contrasty lighting . But in the pic- ture above , the random grouping of candles has created a softer , almost floodlit effect . The high contrast was reduced by the reflec- live white table cloth and slight flame movement during the 4 sec- ond exposure . The light reading was measured from the faces to record them correctly . Notice how the figures were arranged so that they could hold their positions comfortably during the exposure .
The aperture suggested by the meter reading was increased and the development time of the film reduced to avoid reciprocity failure with the long exposure .
Assignment : measuring exposure
Photograph part of a room interior from a viewpoint which includes a window . Use the camera on a tripod . By means of the most appropriate reading technique take the following pictures :
A. One taken during daylight hours ( harsh sunlight should not be shining directly into the room ) . This picture must show maximum detail within the room .
B. One picture under the same lighting conditions but including detail both inside and outside the room .
C. A picture taken after dark using existing room lighting only .
Compare the appearance of the room in each picture and check your exposure accuracy .
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