تويت
التصوير الفوتوغرافي الحديث
تطوير السلبية ..
فحص سلبي ..
ملخص لتأثير التعرض والتطور على الكثافة والتباين
INSPECTING A NEGATIVE
It is sometimes difficult to inspect a negative and really tell whether its exposure and development were correct or not . This is particularly true of smaller negatives developed in ultra - fine grain developers . However , some general rules may be used as guides in judging negatives .
Always judge a negative by looking through it , not at it . Hold it up to a diffused source of light or a well - lighted , white surface and then look at the light source through it . Your viewing light source is quite important . A bright light will blank out thin detail because of its glare . A dim one will show up detail which is too thin to print . If you want to develop your sense of how a negative will print , you must view your negatives with the same light every time .
Probably the simplest negative viewer consists of a standard darkroom safelight fitted with a sheet of opal glass , as shown in Figure 28. With this viewing light , a correctly exposed and developed negative appears fairly thin . The shadow areas have some detail and the highlight areas are semi - transparent . If you place such a negative over some printed material , you should be able to read through the shadows and most of the middle tones . The negative being viewed in Figure 28 is correctly exposed and correctly developed . It appears somewhat thin because it is a studio portrait . Outdoor pictures usually produce denser looking negatives .
Fig . 28 Correctly exposed and correctly developed portrait negative . It is thin but has good shadow detail and clear highlights .
In talking about negatives , two terms are used very frequently , and it is well for the student to thoroughly understand them before going any further . These terms are density and contrast .
It might be well at this point to touch briefly on the difference between density and contrast . Density is used to describe the amount of silver deposited on the negative and nothing more . If the blacks on your negative are heavy and dark , you have a dense negative . If you have an almost transparent image , you have a thin negative , lacking in density . Contrast , on the other hand , is the difference in density between the highlights and shadows of the same negative . You can have high contrast in a dense negative - but you can also have high contrast in a thin negative . Figures 29 through 34 illustrate this point .
An underexposed negative appears thinner than normal and has shadow areas which are either completely clear or have too faint an image to show up in the print . An underdeveloped negative is also thin , but has normal detail in the shadows . You can generally tell underexposure from underdevelopment by examining the shadow areas of the negative . In an underexposed negative they are empty ; in an underdeveloped negative they have almost normal detail but lack density .
An overexposed negative is too dense . An overdeveloped negative is also too dense . It is possible to tell them apart with a little practice by examining the shadows . An overexposed negative has fully exposed shadows with lots of printable detail even in the deep shadows where you would normally not get any . An overdeveloped negative has slightly more than normal density in the shadows , but the deep shadows remain empty .
Table I summarizes this information . Note that the density and appearance of the shadows are the best and most reliable guides to both exposure and development . At first it may be difficult for you to tell when a shadow is too empty to print and , therefore , underexposed . But if you make a print of every negative on normal paper , and then compare the prints with the negatives , you will soon begin to have a visual idea of the relation between negative appearance and the finished print . In the final analysis , it is the print which tells the story .
SUMMARY OF THE EFFECT OF EXPOSURE AND DEVELOPMENT ON DENSITY AND CONTRAST
The image in an exposed and developed film has two important characteristics : density and contrast . Many photographers have a difficult time distinguishing one from the other . Because a clear understanding of these two characteristics is essential to good picture making , let us study them further , even though we have already discussed them in this Assignment .
Density is the overall denseness or blackness of the image , whether it is a negative or print . Contrast is the difference in density between the highlights and shadow areas of the same image . Let us see if we can illustrate this .
Fig . 29 Dense negative with low
contrast .
Fig . 30 Dense negative with normal contrast .
Fig . 31 Dense negative with extreme contrast .
Fig . 32 Thin negative with low contrast .
Fig . 33 Thin negative with normal contrast .
Fig . 34 Thin negative with extreme contrast .
تطوير السلبية ..
فحص سلبي ..
ملخص لتأثير التعرض والتطور على الكثافة والتباين
INSPECTING A NEGATIVE
It is sometimes difficult to inspect a negative and really tell whether its exposure and development were correct or not . This is particularly true of smaller negatives developed in ultra - fine grain developers . However , some general rules may be used as guides in judging negatives .
Always judge a negative by looking through it , not at it . Hold it up to a diffused source of light or a well - lighted , white surface and then look at the light source through it . Your viewing light source is quite important . A bright light will blank out thin detail because of its glare . A dim one will show up detail which is too thin to print . If you want to develop your sense of how a negative will print , you must view your negatives with the same light every time .
Probably the simplest negative viewer consists of a standard darkroom safelight fitted with a sheet of opal glass , as shown in Figure 28. With this viewing light , a correctly exposed and developed negative appears fairly thin . The shadow areas have some detail and the highlight areas are semi - transparent . If you place such a negative over some printed material , you should be able to read through the shadows and most of the middle tones . The negative being viewed in Figure 28 is correctly exposed and correctly developed . It appears somewhat thin because it is a studio portrait . Outdoor pictures usually produce denser looking negatives .
Fig . 28 Correctly exposed and correctly developed portrait negative . It is thin but has good shadow detail and clear highlights .
In talking about negatives , two terms are used very frequently , and it is well for the student to thoroughly understand them before going any further . These terms are density and contrast .
It might be well at this point to touch briefly on the difference between density and contrast . Density is used to describe the amount of silver deposited on the negative and nothing more . If the blacks on your negative are heavy and dark , you have a dense negative . If you have an almost transparent image , you have a thin negative , lacking in density . Contrast , on the other hand , is the difference in density between the highlights and shadows of the same negative . You can have high contrast in a dense negative - but you can also have high contrast in a thin negative . Figures 29 through 34 illustrate this point .
An underexposed negative appears thinner than normal and has shadow areas which are either completely clear or have too faint an image to show up in the print . An underdeveloped negative is also thin , but has normal detail in the shadows . You can generally tell underexposure from underdevelopment by examining the shadow areas of the negative . In an underexposed negative they are empty ; in an underdeveloped negative they have almost normal detail but lack density .
An overexposed negative is too dense . An overdeveloped negative is also too dense . It is possible to tell them apart with a little practice by examining the shadows . An overexposed negative has fully exposed shadows with lots of printable detail even in the deep shadows where you would normally not get any . An overdeveloped negative has slightly more than normal density in the shadows , but the deep shadows remain empty .
Table I summarizes this information . Note that the density and appearance of the shadows are the best and most reliable guides to both exposure and development . At first it may be difficult for you to tell when a shadow is too empty to print and , therefore , underexposed . But if you make a print of every negative on normal paper , and then compare the prints with the negatives , you will soon begin to have a visual idea of the relation between negative appearance and the finished print . In the final analysis , it is the print which tells the story .
SUMMARY OF THE EFFECT OF EXPOSURE AND DEVELOPMENT ON DENSITY AND CONTRAST
The image in an exposed and developed film has two important characteristics : density and contrast . Many photographers have a difficult time distinguishing one from the other . Because a clear understanding of these two characteristics is essential to good picture making , let us study them further , even though we have already discussed them in this Assignment .
Density is the overall denseness or blackness of the image , whether it is a negative or print . Contrast is the difference in density between the highlights and shadow areas of the same image . Let us see if we can illustrate this .
Fig . 29 Dense negative with low
contrast .
Fig . 30 Dense negative with normal contrast .
Fig . 31 Dense negative with extreme contrast .
Fig . 32 Thin negative with low contrast .
Fig . 33 Thin negative with normal contrast .
Fig . 34 Thin negative with extreme contrast .
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