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مبادئ الإضاءة ..
السيطرة على التناقض عن طريق تنويع تطوير الفيلم
CONTROLLING CONTRAST BY VARYING FILM DEVELOPMENT
Before taking up the subject of contrast control through film development control , we would like to anticipate an obvious question and answer it . Why not forget about changing the negative contrast - develop normally and then get the contrast you want by selecting the grade of paper which will give it to you from whatever negatives you get . There are several things wrong with that approach The lighting contrast of a subject in direct sunlight may be so strong that the highlights will block up badly and lose all delicate tone variations when developed normally .
On the other hand , if the lighting is very flat , the negative may be too low in contrast to print on anything but extremely contrasty paper , and such papers are usually poor in their ability to reproduce fine shades of tone accurately . The printer generally prefers to work with negatives that are reasonably similar in contrast as well as density - he can turn out a lot more work that way and his work will be noticeably better .
The commercial photographer who uses sheet film can process each film individually if necessary and he can , by that means , control its contrast to suit the subject . If the subject lighting or subject contrast is excessive , he can cut down development time and reduce contrast in that way . On the other hand , if either lighting or subject contrast is excessively low , he can increase development time .
Even if the photographer uses roll film , he can still attain the same result by keeping all exposures on one roll alike so that the entire roll can be processed for contrast control . It is not practical to cut up a roll into individual sections and process part normally , part for high or low contrast . Automatic contrast control is obtained to a limited degree - at least insofar as avoidance of blocked highlights is concerned - through the use of a compensating film developer . This subject is covered in a later Assignment , but we do want to make the point here that such control is rather limited and it is better to vary development if you want to control negative contrast .
As you were taught in the Assignment covering the development of films , increasing the time of development increases negative contrast , and decreasing development time decreases development contrast . It is generally necessary , however , to vary exposure as well as development time , since exposure also has some effect on contrast .
To reduce contrast , reduce development time . However , in strongly lighted subjects , the shadows tend to be quite dark and empty , and such shadows require full development to bring out any detail at all . To compensate for short development , it is necessary to increase exposure and this will provide enough shadow detail to permit cutting development time in half . The exact amount of overexposure and underdevelopment will depend upon quite a number of factors . These are : subject contrast , lighting contrast , type of film used ( some films are inherently more contrasty than others ) , and the developer ( some developers are more contrasty than others and also some developers respond more strongly to variations in development time ) . As a start , try doubling the exposure and cutting development by 25 % . With experience and a certain amount of trial and error experimentation , you can develop the ability to judge the effect of specific changes in exposure and development time to give you the results you want .
If you want to increase the contrast of your negative because the lighting contrast is poor , as may happen on extremely dull days or in deep shade , you reverse the procedure given above . In other words , you increase development time to build up contrast . This in itself will result in a negative that is too dense if the exposure is correct to begin with , so the obvious answer is to decrease the exposure . Bear aind that with flat lighting , the brightness range between shadows and highlights is much less than normal so that if you take a meter reading in the normal way , the shadows will have good exposure as compared to the highlights - or at least the lighter areas of the subject . This means that you can cut exposure in half without perceptible loss of shadow detail . In other words , to increase contrast for very flatly lighted subjects , the answer is to cut exposure and increase development time .
Here too , the degree to which exposure should be reduced and development increased depends on a number of factors . As a rough guide , try cutting the exposure in half and increasing development time by 50 % . Note that in this case the time of development was changed by a wider margin than in the case of overexposure and underdevelopment . This is because developers do not act uniformly with respect to time . The development process starts fairly rapidly at first and then gradually slows down . For a corresponding increase in development contrast , you must increase development to a higher degree .
One final word before we leave this subject of contrast control . There will be occasions when you simply will not have the opportunity of exercising much control over daylight . You may have to shoot in a hurry and have no time to look for a better lighting situation , or the exposure may be only one in a full roll of normal subjects and you cannot give it special treatment . In that case , shoot for picture interest rather than technical excellence . If you are photographing a model or making a portrait , do everything you can to get life and sparkle into the subject's expression . Shoot for human interest if you can . Try to build up the composition as much as possible . By going all out on such matters as these , you can often relegate technical excellence to a secondary position and still come up with a highly successful picture .
مبادئ الإضاءة ..
السيطرة على التناقض عن طريق تنويع تطوير الفيلم
CONTROLLING CONTRAST BY VARYING FILM DEVELOPMENT
Before taking up the subject of contrast control through film development control , we would like to anticipate an obvious question and answer it . Why not forget about changing the negative contrast - develop normally and then get the contrast you want by selecting the grade of paper which will give it to you from whatever negatives you get . There are several things wrong with that approach The lighting contrast of a subject in direct sunlight may be so strong that the highlights will block up badly and lose all delicate tone variations when developed normally .
On the other hand , if the lighting is very flat , the negative may be too low in contrast to print on anything but extremely contrasty paper , and such papers are usually poor in their ability to reproduce fine shades of tone accurately . The printer generally prefers to work with negatives that are reasonably similar in contrast as well as density - he can turn out a lot more work that way and his work will be noticeably better .
The commercial photographer who uses sheet film can process each film individually if necessary and he can , by that means , control its contrast to suit the subject . If the subject lighting or subject contrast is excessive , he can cut down development time and reduce contrast in that way . On the other hand , if either lighting or subject contrast is excessively low , he can increase development time .
Even if the photographer uses roll film , he can still attain the same result by keeping all exposures on one roll alike so that the entire roll can be processed for contrast control . It is not practical to cut up a roll into individual sections and process part normally , part for high or low contrast . Automatic contrast control is obtained to a limited degree - at least insofar as avoidance of blocked highlights is concerned - through the use of a compensating film developer . This subject is covered in a later Assignment , but we do want to make the point here that such control is rather limited and it is better to vary development if you want to control negative contrast .
As you were taught in the Assignment covering the development of films , increasing the time of development increases negative contrast , and decreasing development time decreases development contrast . It is generally necessary , however , to vary exposure as well as development time , since exposure also has some effect on contrast .
To reduce contrast , reduce development time . However , in strongly lighted subjects , the shadows tend to be quite dark and empty , and such shadows require full development to bring out any detail at all . To compensate for short development , it is necessary to increase exposure and this will provide enough shadow detail to permit cutting development time in half . The exact amount of overexposure and underdevelopment will depend upon quite a number of factors . These are : subject contrast , lighting contrast , type of film used ( some films are inherently more contrasty than others ) , and the developer ( some developers are more contrasty than others and also some developers respond more strongly to variations in development time ) . As a start , try doubling the exposure and cutting development by 25 % . With experience and a certain amount of trial and error experimentation , you can develop the ability to judge the effect of specific changes in exposure and development time to give you the results you want .
If you want to increase the contrast of your negative because the lighting contrast is poor , as may happen on extremely dull days or in deep shade , you reverse the procedure given above . In other words , you increase development time to build up contrast . This in itself will result in a negative that is too dense if the exposure is correct to begin with , so the obvious answer is to decrease the exposure . Bear aind that with flat lighting , the brightness range between shadows and highlights is much less than normal so that if you take a meter reading in the normal way , the shadows will have good exposure as compared to the highlights - or at least the lighter areas of the subject . This means that you can cut exposure in half without perceptible loss of shadow detail . In other words , to increase contrast for very flatly lighted subjects , the answer is to cut exposure and increase development time .
Here too , the degree to which exposure should be reduced and development increased depends on a number of factors . As a rough guide , try cutting the exposure in half and increasing development time by 50 % . Note that in this case the time of development was changed by a wider margin than in the case of overexposure and underdevelopment . This is because developers do not act uniformly with respect to time . The development process starts fairly rapidly at first and then gradually slows down . For a corresponding increase in development contrast , you must increase development to a higher degree .
One final word before we leave this subject of contrast control . There will be occasions when you simply will not have the opportunity of exercising much control over daylight . You may have to shoot in a hurry and have no time to look for a better lighting situation , or the exposure may be only one in a full roll of normal subjects and you cannot give it special treatment . In that case , shoot for picture interest rather than technical excellence . If you are photographing a model or making a portrait , do everything you can to get life and sparkle into the subject's expression . Shoot for human interest if you can . Try to build up the composition as much as possible . By going all out on such matters as these , you can often relegate technical excellence to a secondary position and still come up with a highly successful picture .
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