تويت
التصوير الفوتوغرافي الحديث
معدات الغرفة المظلمة ..
الأمان ..
تحديد موقع الأمان ..
SAFELIGHTS
The high speed panchromatic films generally used today are so sensitive to all colors of light that they must be handled in complete darkness . In those circumstances where it is necessary to have some light , the illumination is provided by very dim green light . This color is chosen because the eye has a relatively high sensitivity green , and panchromatic film usually has less sensitivity to green than to red or blue . Green light can , therefore , be considered at least to some extent a safe light for panchromatic film if the intensity is kept low enough .
Enlarging papers are very much slower than films and they are not panchromatic . Their sensitivity is largely to the blue , with certain papers extending their sensitivity slightly into the green . For such papers , a safe light could be amber , orange or red .
The manufacturers of the various sensitive emulsions provide information as to the color of safe light which may be used for any particular emulsion to give maximum visibility consistent with safety . Lamps which provide such safe light through the use of special large filters are obtainable in practically any camera store and such lamps are called safelights . Typical safelights are shown in Figures 14 , 15 and 16 .
It is important that the safelight be provided with the correct safelight filter for the sensitized material with which it is to be used . Only in this way can you obtain the maximum amount of light consistent with safety , and the high level of illumination essential to good work . It is for this reason that manufacturers of sensitized photographic material always specify the color of the safelight filter which gives maximum safe illumination for their various products . Even here , it is important to understand that safety is a relative term . By this we mean that the total level of illumination as well as its color are factors . For example , even if a recommended safe light is used for a particular brand of enlarging paper , it can still be fogged if the lamp in the safelight is brighter than is recommended , or if the sensitized material is exposed to the safe light for excessively long periods .
LOCATING THE SAFELIGHTS
The placement of a safelight is as important as the amount of light it provides . The placement , of course , is determined by the use to which the light is to be put . Figure 14 shows a safelight that is designed to provide a general overall illumination of a relatively low value throughout the darkroom . Such general over all illimination should be supple mented by additional small safe lights which provide higher area illumination at specific areas such as over the processing trays . Safelights intended primarily for such local illumination are shown in Figures 15 and 16. How best to combine overall illumination and local illumination will
Figure 14 Large safelight ( hanging from ceiling ) used for general overall illumination in the dark room .
depend upon the size of the dark room , the location of the various work areas and other considerations of a like nature . General illumination is seldom if ever required in a dark room that is devoted exclusively to the processing of film , since most of them must be handled in complete darkness . However , local illumination may sometimes be necessary , as , for example , the illumination of a timer or clock . A timer can be illuminated adequately without danger fogging panchromatic film by mounting small safelight equipped with deep green filter in front of the timer in such a way that the face of the timer is illuminated , but no direct light can ever reach the film . A similar arrange ment can be used in the enlarging room , but there the light can be quite a bit stronger . As a matter of fact , an ordinary small red lamp such as is used for Christmas tree lighting may be used provided it is well shaded and only a narrow beam of light reaches the clock face itself .
Figure 15 Simple safelight lamp with separ able mounting bracket .
A useful accessory for providing some I light in the film developing or handling i room in an emergency is to have a small hand flashlight fitted with a Wratten Series 3 safelight filter instead of the usual clear glass or plastic . Before using it , check it carefully to make sure that no white light gets through . If there is any light leakage , use some electrical tape to cover the leak .
The subject of safelight placement for maximum utilization in the enlarging or printing room was discussed earlier in this Assignment .
Figure 16 A safelight used for local illumination .
معدات الغرفة المظلمة ..
الأمان ..
تحديد موقع الأمان ..
SAFELIGHTS
The high speed panchromatic films generally used today are so sensitive to all colors of light that they must be handled in complete darkness . In those circumstances where it is necessary to have some light , the illumination is provided by very dim green light . This color is chosen because the eye has a relatively high sensitivity green , and panchromatic film usually has less sensitivity to green than to red or blue . Green light can , therefore , be considered at least to some extent a safe light for panchromatic film if the intensity is kept low enough .
Enlarging papers are very much slower than films and they are not panchromatic . Their sensitivity is largely to the blue , with certain papers extending their sensitivity slightly into the green . For such papers , a safe light could be amber , orange or red .
The manufacturers of the various sensitive emulsions provide information as to the color of safe light which may be used for any particular emulsion to give maximum visibility consistent with safety . Lamps which provide such safe light through the use of special large filters are obtainable in practically any camera store and such lamps are called safelights . Typical safelights are shown in Figures 14 , 15 and 16 .
It is important that the safelight be provided with the correct safelight filter for the sensitized material with which it is to be used . Only in this way can you obtain the maximum amount of light consistent with safety , and the high level of illumination essential to good work . It is for this reason that manufacturers of sensitized photographic material always specify the color of the safelight filter which gives maximum safe illumination for their various products . Even here , it is important to understand that safety is a relative term . By this we mean that the total level of illumination as well as its color are factors . For example , even if a recommended safe light is used for a particular brand of enlarging paper , it can still be fogged if the lamp in the safelight is brighter than is recommended , or if the sensitized material is exposed to the safe light for excessively long periods .
LOCATING THE SAFELIGHTS
The placement of a safelight is as important as the amount of light it provides . The placement , of course , is determined by the use to which the light is to be put . Figure 14 shows a safelight that is designed to provide a general overall illumination of a relatively low value throughout the darkroom . Such general over all illimination should be supple mented by additional small safe lights which provide higher area illumination at specific areas such as over the processing trays . Safelights intended primarily for such local illumination are shown in Figures 15 and 16. How best to combine overall illumination and local illumination will
Figure 14 Large safelight ( hanging from ceiling ) used for general overall illumination in the dark room .
depend upon the size of the dark room , the location of the various work areas and other considerations of a like nature . General illumination is seldom if ever required in a dark room that is devoted exclusively to the processing of film , since most of them must be handled in complete darkness . However , local illumination may sometimes be necessary , as , for example , the illumination of a timer or clock . A timer can be illuminated adequately without danger fogging panchromatic film by mounting small safelight equipped with deep green filter in front of the timer in such a way that the face of the timer is illuminated , but no direct light can ever reach the film . A similar arrange ment can be used in the enlarging room , but there the light can be quite a bit stronger . As a matter of fact , an ordinary small red lamp such as is used for Christmas tree lighting may be used provided it is well shaded and only a narrow beam of light reaches the clock face itself .
Figure 15 Simple safelight lamp with separ able mounting bracket .
A useful accessory for providing some I light in the film developing or handling i room in an emergency is to have a small hand flashlight fitted with a Wratten Series 3 safelight filter instead of the usual clear glass or plastic . Before using it , check it carefully to make sure that no white light gets through . If there is any light leakage , use some electrical tape to cover the leak .
The subject of safelight placement for maximum utilization in the enlarging or printing room was discussed earlier in this Assignment .
Figure 16 A safelight used for local illumination .
تعليق