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الحبيبات - ١ - اختيار الفيلم .. كيفية التقاط وتطوير الصور بالأبيض والأسود
GRAININESS
Graininess is a purely photographic quality . It comes from the process of pho- tography , and not from the scene or subject . Practically , it is one of the most important image qualities , and is more noticeable in a black - and - white picture than in colour . This is because the grains in a black - and - white negative are solid black , whereas developed colour film has instead overlapping patches of trans- parent dye in three hues , giving a less distinct effect . Whether you consider graininess as interfering with the image or adding to it is a matter of opinion , but how visible it is depends on the type of film , how you develop it , and the degree of enlargement .
The picture opposite shows typical graininess - a speckled texture . What you see here , however , is not the individual grains themselves ; they are far too small to be distinguished by the naked eye . Graininess is the appearance of clumps of many grains , overlapping each other in what is a relatively thick layer of emulsion . The grains are jumbled and stacked on top of each other . Never- theless , graininess reflects granularity , which is the actual measurement of how big and prominent the grains are .
Graininess runs hand in hand with film speed , as is easy enough to see by making a direct comparison between slow , medium and fast film . Photograph the same scene with each in turn ; with the only change to the camera and lens being the exposure setting . The difference in the finished print is obvious .
Now , the important result of making this comparison is the most obvious one : graininess only becomes apparent beyond a certain enlargement . The set of full frames printed here from 35mm negatives are not big enough to show any significant difference . This is a valuable exercise to do for yourself , and it will help you in deciding when to use films of different speeds . By experiment- ing with different enlarger settings , find the degree of enlargement at which you can just detect a grainy texture with each of the three speed categories .
ISO Ratings
Compare the difference in graininess of these three films with different ISO ratings . The print ( below left ) was taken from the Plus - X film , which has the rating most commonly found .
Panatomic - X , ISO 25 ; very fine grain
Plus - X , ISP 100 ; medium grain .
Tri - X , ISO 400 ; fast , grainy .
ABOVE AND INSET Graininess creates its own mood , as in this portrait , and should not therefore be seen as inherently detrimental to good prints .
The amount of graininess from any particular film is not necessarily consist- ent . One other action can affect it : the development . As we will see later , in the section on processing , there are different kinds of developer , and one type is designed to reduce the way in which the silver grains clump together . Known as extra - fine - grain developer , it reduces graininess in any film , although at the expense of speed and contrast . The opposite effect of enhanced graininess occurs if a high - energy developer is used . This is chosen principally to increase the speed performance of film , and makes the grain clumps appear coarser . Over - development increases graininess , under - development reduces it .
GRAININESS
Graininess is a purely photographic quality . It comes from the process of pho- tography , and not from the scene or subject . Practically , it is one of the most important image qualities , and is more noticeable in a black - and - white picture than in colour . This is because the grains in a black - and - white negative are solid black , whereas developed colour film has instead overlapping patches of trans- parent dye in three hues , giving a less distinct effect . Whether you consider graininess as interfering with the image or adding to it is a matter of opinion , but how visible it is depends on the type of film , how you develop it , and the degree of enlargement .
The picture opposite shows typical graininess - a speckled texture . What you see here , however , is not the individual grains themselves ; they are far too small to be distinguished by the naked eye . Graininess is the appearance of clumps of many grains , overlapping each other in what is a relatively thick layer of emulsion . The grains are jumbled and stacked on top of each other . Never- theless , graininess reflects granularity , which is the actual measurement of how big and prominent the grains are .
Graininess runs hand in hand with film speed , as is easy enough to see by making a direct comparison between slow , medium and fast film . Photograph the same scene with each in turn ; with the only change to the camera and lens being the exposure setting . The difference in the finished print is obvious .
Now , the important result of making this comparison is the most obvious one : graininess only becomes apparent beyond a certain enlargement . The set of full frames printed here from 35mm negatives are not big enough to show any significant difference . This is a valuable exercise to do for yourself , and it will help you in deciding when to use films of different speeds . By experiment- ing with different enlarger settings , find the degree of enlargement at which you can just detect a grainy texture with each of the three speed categories .
ISO Ratings
Compare the difference in graininess of these three films with different ISO ratings . The print ( below left ) was taken from the Plus - X film , which has the rating most commonly found .
Panatomic - X , ISO 25 ; very fine grain
Plus - X , ISP 100 ; medium grain .
Tri - X , ISO 400 ; fast , grainy .
ABOVE AND INSET Graininess creates its own mood , as in this portrait , and should not therefore be seen as inherently detrimental to good prints .
The amount of graininess from any particular film is not necessarily consist- ent . One other action can affect it : the development . As we will see later , in the section on processing , there are different kinds of developer , and one type is designed to reduce the way in which the silver grains clump together . Known as extra - fine - grain developer , it reduces graininess in any film , although at the expense of speed and contrast . The opposite effect of enhanced graininess occurs if a high - energy developer is used . This is chosen principally to increase the speed performance of film , and makes the grain clumps appear coarser . Over - development increases graininess , under - development reduces it .
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