تويت
التصوير الفوتوغرافي الحديث
تطوير السلبية ..
تأثير التعرض وتطوير الجودة السلبية
EFFECT OF EXPOSURE
AND DEVELOPMENT ON NEGATIVE QUALITY
The two main factors that govern the quality of a negative are exposure and development . Exposure is either correct , over ( too much ) , or under ( too little ) , and development also is either correct , over , or under . Therefore , there are nine possible combinations of exposure and development . These are given below :
Exposure - - - Development
1 . correct - - - correct
2 . correct - - - too much
3 . correct - - - too little
4 . over - - - correct
5 . over - - - too much
6 . over - - - too much
7 . under - - - correct
8 . under - - - too much
9 . under - - - too little
A negative that has received correct exposure and correct development is a the normal negative that will give a good print on a normal grade of paper . This . kind of negative you want to get every time you make an exposure .
A correctly exposed negative that has been overdeveloped will have too . much contrast and will need a soft paper , while a correctly exposed negative that has been underdeveloped will be weak and lacking in contrast , and will call for a hard paper .
EFFECT OF DEVELOPMENT . The variation in contrast with development is due to the fact that in the process of development of a normally exposed negative , the highlights ( dense areas ) and shadows ( thin areas ) increase in density at different rates the highlights depositing silver rapidly , and the shadow tones much more . slowly . Therefore , in the development of the negative , you can control the contrast simply by regulating the time of development .
Short development will give a short range of contrast , and prolonged development will give a long range with considerable difference in density . between the highlights and the shadows . This is an important point to bear in mind because the possibility of control over the contrast of a negative is extremely useful .
Different printing processes call for different types of negatives to give the best results . The best kind of negative for making an enlargement is the one that is moderately thin and soft , without too much contrast . A highly efficient condenser - type enlarger requires a softer and thinner negative than does a diffusion enlarger . Contact printing , on the other hand , calls for a negative with a good range of tones and good contrast between the highlights and shadows .
The change in contrast that you can get by regulating the time of development makes it possible for you to adapt a negative to the printing process . you want to use . If you are planning to make enlargements from the negative , you would keep it thin and soft , but you would develop it longer and make it stronger and more contrasty if you intended to make contact prints from it . Similarly , if you were to make a portrait of a girl , you would want a fairly soft negative , so you would keep the development on the short side ; if you were to make a commercial picture for a catalog illustration , you would want more contrast , so you would develop slightly longer .
NORMALLY EXPOSED NEGATIVES . As a rule , a correctly exposed film that has received normal development will give a normal , well - graded negative that can be properly printed on a normal paper . If this correctly exposed film has been overdeveloped , its contrasts will be greater , the scale of tones or gradations will be wider , and it will call for a printing paper of a softer grade to counteract its excessive contrast . A correctly exposed film that has been underdeveloped will be lacking in contrast , its range of tones will be narrower , and it will call for the use of a paper that will produce more snap - in other words , a hard paper .
Of course , the choice of paper depends to a certain extent on personal preference ; some photographers like a soft print , while others prefer one that is snappier or more contrasty .
OVEREXPOSED NEGATIVES . A grossly overexposed negative of an average subject made with normal lighting will tend to flat . However , if the lighting itself is very contrasty , this may not be entirely true . For example , if you should take a picture of an average outdoor landscape without many deep shadows and overexpose it badly , the negative would be both dense and flat . You can get a passable print from such a negative by using a contrasty paper . If the printing time is too long , you can reduce the negative chemically . It would be best to use the type of reducer that increases contrast while reduces , as will be explained in a later Assignment .
On the other hand , let us say you took a portrait indoors and used harsh lighting so that the face of your subject was strongly lighted on one side , but in deep shadow on the other side . If you overexposed badly , the lighted portion of the face would be very dense while the shadow portion would still be fairly clear . In that respect , your negative would be too contrasty because the difference in density between the highlights and shadows would be very great . Nevertheless , you wouldn't be able to make a satisfactory print on soft paper from such a negative . Let us consider why .
Actually , you did not overexpose the shadows - they were so dark that they required many times the average exposure to show any detail . The highlights in the face , however , were a different matter . There you did overexpose . This means that if you look at the lighter part of the face alone , you find that it is too flat - that is , there is very little difference between the highest highlight and the less strongly lighted highlights , so that except for the deep shadows , the entire face is a uniform , uninteresting white without any roundness or modeling .
A negative of this kind is hopeless and can't be printed properly on any kind of paper . We need a contrasty paper to separate the tones in the lighted part of the face , yet we need a soft paper to being together the shadows and highlights . That is why correct exposure and proper lighting are so extremely important in portraiture .
An overexposed negative that is underdeveloped will have an even shorter range of tones and will need a very contrasty grade of paper . An overexposed , overdeveloped negative will be very dense and black ; it will need a long exposure in printing . It may require either a soft or contrasty grade of printing paper , depending upon the contrast of the lighting and whether the overexposure leads to flatness , was carried further than the overdevelopment , which increases contrast . All overexposed negatives can be very much improved by reduction and sometimes by both reduction and intensification . These are chemical processes that will be fully explained to you in a later Assignment .
UNDEREXPOSED NEGATIVES . A badly underexposed negative will have completely empty shadows and no amount of after - treatment will do much good . If it is only slightly underexposed , however , it will be rather thin and soft , and so you may be able to save it by using a very contrasty paper or by intensification , which will build up the thin image and give it enough contrast .
تطوير السلبية ..
تأثير التعرض وتطوير الجودة السلبية
EFFECT OF EXPOSURE
AND DEVELOPMENT ON NEGATIVE QUALITY
The two main factors that govern the quality of a negative are exposure and development . Exposure is either correct , over ( too much ) , or under ( too little ) , and development also is either correct , over , or under . Therefore , there are nine possible combinations of exposure and development . These are given below :
Exposure - - - Development
1 . correct - - - correct
2 . correct - - - too much
3 . correct - - - too little
4 . over - - - correct
5 . over - - - too much
6 . over - - - too much
7 . under - - - correct
8 . under - - - too much
9 . under - - - too little
A negative that has received correct exposure and correct development is a the normal negative that will give a good print on a normal grade of paper . This . kind of negative you want to get every time you make an exposure .
A correctly exposed negative that has been overdeveloped will have too . much contrast and will need a soft paper , while a correctly exposed negative that has been underdeveloped will be weak and lacking in contrast , and will call for a hard paper .
EFFECT OF DEVELOPMENT . The variation in contrast with development is due to the fact that in the process of development of a normally exposed negative , the highlights ( dense areas ) and shadows ( thin areas ) increase in density at different rates the highlights depositing silver rapidly , and the shadow tones much more . slowly . Therefore , in the development of the negative , you can control the contrast simply by regulating the time of development .
Short development will give a short range of contrast , and prolonged development will give a long range with considerable difference in density . between the highlights and the shadows . This is an important point to bear in mind because the possibility of control over the contrast of a negative is extremely useful .
Different printing processes call for different types of negatives to give the best results . The best kind of negative for making an enlargement is the one that is moderately thin and soft , without too much contrast . A highly efficient condenser - type enlarger requires a softer and thinner negative than does a diffusion enlarger . Contact printing , on the other hand , calls for a negative with a good range of tones and good contrast between the highlights and shadows .
The change in contrast that you can get by regulating the time of development makes it possible for you to adapt a negative to the printing process . you want to use . If you are planning to make enlargements from the negative , you would keep it thin and soft , but you would develop it longer and make it stronger and more contrasty if you intended to make contact prints from it . Similarly , if you were to make a portrait of a girl , you would want a fairly soft negative , so you would keep the development on the short side ; if you were to make a commercial picture for a catalog illustration , you would want more contrast , so you would develop slightly longer .
NORMALLY EXPOSED NEGATIVES . As a rule , a correctly exposed film that has received normal development will give a normal , well - graded negative that can be properly printed on a normal paper . If this correctly exposed film has been overdeveloped , its contrasts will be greater , the scale of tones or gradations will be wider , and it will call for a printing paper of a softer grade to counteract its excessive contrast . A correctly exposed film that has been underdeveloped will be lacking in contrast , its range of tones will be narrower , and it will call for the use of a paper that will produce more snap - in other words , a hard paper .
Of course , the choice of paper depends to a certain extent on personal preference ; some photographers like a soft print , while others prefer one that is snappier or more contrasty .
OVEREXPOSED NEGATIVES . A grossly overexposed negative of an average subject made with normal lighting will tend to flat . However , if the lighting itself is very contrasty , this may not be entirely true . For example , if you should take a picture of an average outdoor landscape without many deep shadows and overexpose it badly , the negative would be both dense and flat . You can get a passable print from such a negative by using a contrasty paper . If the printing time is too long , you can reduce the negative chemically . It would be best to use the type of reducer that increases contrast while reduces , as will be explained in a later Assignment .
On the other hand , let us say you took a portrait indoors and used harsh lighting so that the face of your subject was strongly lighted on one side , but in deep shadow on the other side . If you overexposed badly , the lighted portion of the face would be very dense while the shadow portion would still be fairly clear . In that respect , your negative would be too contrasty because the difference in density between the highlights and shadows would be very great . Nevertheless , you wouldn't be able to make a satisfactory print on soft paper from such a negative . Let us consider why .
Actually , you did not overexpose the shadows - they were so dark that they required many times the average exposure to show any detail . The highlights in the face , however , were a different matter . There you did overexpose . This means that if you look at the lighter part of the face alone , you find that it is too flat - that is , there is very little difference between the highest highlight and the less strongly lighted highlights , so that except for the deep shadows , the entire face is a uniform , uninteresting white without any roundness or modeling .
A negative of this kind is hopeless and can't be printed properly on any kind of paper . We need a contrasty paper to separate the tones in the lighted part of the face , yet we need a soft paper to being together the shadows and highlights . That is why correct exposure and proper lighting are so extremely important in portraiture .
An overexposed negative that is underdeveloped will have an even shorter range of tones and will need a very contrasty grade of paper . An overexposed , overdeveloped negative will be very dense and black ; it will need a long exposure in printing . It may require either a soft or contrasty grade of printing paper , depending upon the contrast of the lighting and whether the overexposure leads to flatness , was carried further than the overdevelopment , which increases contrast . All overexposed negatives can be very much improved by reduction and sometimes by both reduction and intensification . These are chemical processes that will be fully explained to you in a later Assignment .
UNDEREXPOSED NEGATIVES . A badly underexposed negative will have completely empty shadows and no amount of after - treatment will do much good . If it is only slightly underexposed , however , it will be rather thin and soft , and so you may be able to save it by using a very contrasty paper or by intensification , which will build up the thin image and give it enough contrast .
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