تويت
التصوير الفوتوغرافي الحديث
فن النسخ
الإضاءة
LIGHTING
For copying in black - and - white , almost any convenient lamps may be used provided they are equipped with reflectors to keep the light from shining on the lens . The reflectors may be quite small and simple , as shown in the illustrations of copy equipment , or they may be of the mushroom type with their own built - in reflectors , such as the Reflectorfloods .
If color film is being used in the camera , then , of course , proper attention should be paid to matching the color temperature of the light to the film . This point has been discussed a number of times in earlier Assignments , so we won't repeat that discussion here .
Perhaps the most important factor in producing a successful copy is to illuminate the original with absolute uniformity over its entire area . Nothing will attract so much attention and cause as much dissatisfaction as an incorrectly illuminated original .
You can obtain uniform illumination of the material to be copied by using two identical lamps in the same relative position on two opposite sides of the easel , as illustrated in Figure 23. If the camera has a relatively short focal length lens , the lamps are usually positioned at an angle of 45 ° to the easel ; if the lens has a long focal length , the lights may be at an angle of from 20 ° to 30 ° . The 45 ° angle is recommended for general use and the narrow angle for use with copy having troublesome reflections .
( In copy work , it is customary practice to call the material that is to be copied , " the copy . " This can be misleading if you are not careful . )
Figure 23 Correct lighting setup ( as seen from above ) . This arrangement will provide even illumination over entire easel area .
Figure 24 To test the evenness of the lighting arrangement shown in Figure 23 , hold a pencil . close to and in the center of the copy board two shadows are of equal darkness , the lighting will be even .
The lighting must always be checked for uniformity just before the exposure is made , even if the lights are equally spaced from the copy . As lamps get old , the amount of light they emit falls off , so that except when they are brand new , two apparently identical lamps do not necessarily provide equal illumination . This is particularly true of photoflood lamps .
An exposure meter is valuable in checking the evenness of illumination . Place a large matte - surfaced card or board against the easel in front of the copy and , holding the meter a few inches from its surface , take readings in the center and at all four sides and corners . Be careful that the shadow of the meter does not fall on the card within the acceptance angle of the meter or you will get an incorrect reading . If the meter reading is not uniform within one third stop over the entire area to be copied , move the lights as necessary until it is .
If you are copying only a small area , the meter method may not be good enough to provide accurate information as to evenness of illumination . The pencil method is an old standby in such cases . Hold a pencil about an inch in front of the easel , as shown in Figure 24. You should see two identical shadows , one from each lamp . If one shadow is darker than the other , the lamp causing it is throwing more light on the easel . Move this lamp back ( or the other forward ) until both shadows are equally dark .
REFLECTIONS . Reflections from the copy or the copy easel may be very troublesome . There are a number of ways to reduce them to values which are negligible . Paint the easel black or some other dark color , and see to it that no brightly illuminated objects other than the copy material are in front of the If the copy material is glossy so that reflection from its surface is very pronounced , you may have to use either a very narrow or very wide angle for the lights .
Polarizing Screens . Polarizing screens and filters provide the best means of reducing troublesome reflections . A great deal of control of specular reflections from the copy ( which produce bright glare spots ) may be obtained with a polarizing filter in front of the lens . Using polarizing screens in front of the lights in addition to a polarizing filter stops practically all specular reflections , and only the diffused reflections from the original are photographed .
Rotating the polarizing filter in front of the lens permits varying amounts of specular reflections to pass through the lens . The effect can be observed on the groundglass viewing directly through the polarizing filter . This control is valuable in reproducing oil paintings and other art work where the elimination of all specular reflection may result in a rendition that is different from that which the artist intended .
فن النسخ
الإضاءة
LIGHTING
For copying in black - and - white , almost any convenient lamps may be used provided they are equipped with reflectors to keep the light from shining on the lens . The reflectors may be quite small and simple , as shown in the illustrations of copy equipment , or they may be of the mushroom type with their own built - in reflectors , such as the Reflectorfloods .
If color film is being used in the camera , then , of course , proper attention should be paid to matching the color temperature of the light to the film . This point has been discussed a number of times in earlier Assignments , so we won't repeat that discussion here .
Perhaps the most important factor in producing a successful copy is to illuminate the original with absolute uniformity over its entire area . Nothing will attract so much attention and cause as much dissatisfaction as an incorrectly illuminated original .
You can obtain uniform illumination of the material to be copied by using two identical lamps in the same relative position on two opposite sides of the easel , as illustrated in Figure 23. If the camera has a relatively short focal length lens , the lamps are usually positioned at an angle of 45 ° to the easel ; if the lens has a long focal length , the lights may be at an angle of from 20 ° to 30 ° . The 45 ° angle is recommended for general use and the narrow angle for use with copy having troublesome reflections .
( In copy work , it is customary practice to call the material that is to be copied , " the copy . " This can be misleading if you are not careful . )
Figure 23 Correct lighting setup ( as seen from above ) . This arrangement will provide even illumination over entire easel area .
Figure 24 To test the evenness of the lighting arrangement shown in Figure 23 , hold a pencil . close to and in the center of the copy board two shadows are of equal darkness , the lighting will be even .
The lighting must always be checked for uniformity just before the exposure is made , even if the lights are equally spaced from the copy . As lamps get old , the amount of light they emit falls off , so that except when they are brand new , two apparently identical lamps do not necessarily provide equal illumination . This is particularly true of photoflood lamps .
An exposure meter is valuable in checking the evenness of illumination . Place a large matte - surfaced card or board against the easel in front of the copy and , holding the meter a few inches from its surface , take readings in the center and at all four sides and corners . Be careful that the shadow of the meter does not fall on the card within the acceptance angle of the meter or you will get an incorrect reading . If the meter reading is not uniform within one third stop over the entire area to be copied , move the lights as necessary until it is .
If you are copying only a small area , the meter method may not be good enough to provide accurate information as to evenness of illumination . The pencil method is an old standby in such cases . Hold a pencil about an inch in front of the easel , as shown in Figure 24. You should see two identical shadows , one from each lamp . If one shadow is darker than the other , the lamp causing it is throwing more light on the easel . Move this lamp back ( or the other forward ) until both shadows are equally dark .
REFLECTIONS . Reflections from the copy or the copy easel may be very troublesome . There are a number of ways to reduce them to values which are negligible . Paint the easel black or some other dark color , and see to it that no brightly illuminated objects other than the copy material are in front of the If the copy material is glossy so that reflection from its surface is very pronounced , you may have to use either a very narrow or very wide angle for the lights .
Polarizing Screens . Polarizing screens and filters provide the best means of reducing troublesome reflections . A great deal of control of specular reflections from the copy ( which produce bright glare spots ) may be obtained with a polarizing filter in front of the lens . Using polarizing screens in front of the lights in addition to a polarizing filter stops practically all specular reflections , and only the diffused reflections from the original are photographed .
Rotating the polarizing filter in front of the lens permits varying amounts of specular reflections to pass through the lens . The effect can be observed on the groundglass viewing directly through the polarizing filter . This control is valuable in reproducing oil paintings and other art work where the elimination of all specular reflection may result in a rendition that is different from that which the artist intended .
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