تويت
الخطوة 1: الفيلم الملون / الأنواع والبنية .. التصوير الملون .. المرشد خطوة بخطوة للتصوير الفوتوغرافي
STEP 1 : COLOR FILM / Types and structure
There are two main factors to consider when choosing color film . First , the form you want your result to take - slide , print , or perhaps both . And second , the lighting you will be using to take the pictures . Different types of film must be used under daylight and tungsten ( artificial ) lighting .
Modern color films produce either slides ( color transparencies ) or color negatives ( for color prints ) . Black and white prints can be obtained from both types of film . The final form of your image is not fixed by the film you use . You can obtain slides from negatives , or prints from slides ( see pp . 172- 5 ) . But the best all - round results are achiev- ed when you use the film that gives you the final form you want transparencies or prints . A third type of color film - instant picture film is discussed on page 210 .
Color slide film
Slide film , also called reversal film , is given a processing sequence which forms positive images directly on the film taken from the camera . These transparencies can either be projected on to a screen or looked at in a hand viewer . You can process most color slide films , such as Ektachrome and Agfa- chrome , yourself , as explained on page 164 . A few types , such as Kodachrome , have a particular chemical structure which means that the processing must be done by the manufacturers or their agents .
Using color slide film has several advan- tages . You can do your own processing without a darkroom or any special equip- ment . Color slides , shown on a good pro- jector in a blacked out room , give images . that are unrivalled for fine detail , brilliance , and accuracy of color . Another consider- ation in favor of color slide film is that in terms of cost per picture , slides are the cheapest form of color photography .
Color negative film
All color negative films can be home pro- cessed . In processing , they follow a simpler sequence of stages than slide film to produce an image with negative tone values and complementary ( or " opposite " ) colors . Like a black and white negative , this is an inter- mediate form from which positive prints can be made on photographic paper for which you require a darkroom . You will need much of the equipment used in black and white printing , shown in the larger dark- room on page 74 .
Unlike color slide film , negatives allow you to lighten or darken the image during . printing , and adjust the colors by filtering . Color prints are a convenient form for your pictures , and you can make many prints from the same negative .
Daylight and tungsten film
Each layer is sensitive to one of the three primary colors - blue , green , and red - from which all other colors are composed . The sensitivity of all three emulsion layers of the film is carefully " balanced " to record and reproduce colors and tones acceptably .
Most color films are balanced for subjects lit by daylight . Tungsten lighting produces slightly more red and less blue wavelengths than daylight . This is not normally notice- able because our eyes quickly adapt when changing from outdoor daylight to tungsten lit , indoor surroundings . Unlike our eyes color film is fixed in its response . Con- sequently , daylight balanced films give results with a strong orange cast if the sub- ject is in tungsten light . If you use a film balanced for tungsten lighting in daylight conditions , the results will appear blue .
If you are using color negative film with the wrong light source , you can , to some extent , correct for this when printing . But this should be avoided as the heavy filtering required often obstructs other , more subtle color controls .
For the best results use daylight and tungsten films only in the lighting for which they are intended . Try to avoid subjects lit by a mixture of daylight and tungsten light unless noticeable differences in color are part of the effect you want . On page 146 you can see how to use correction filters with tungsten or daylight film to compensate for incorrect lighting .
Speed and brand
The speed ratings of color films for general photography range from 25 ASA ( Koda- chrome ) , the slowest , to 400 ASA ( Koda- color and Fujicolor ) , the fastest color film available . As in black and white photo- graphy , the appearance of fine detail deterio- rates and grain becomes more noticeable with faster film . In extreme cases , particu- larly when very fast film is overdeveloped , tiny irregular globules of color can be seen in enlargements . For maximum resolution of detail , you should use the slowest film that lighting conditions will allow .
Each make and brand of color film gives slightly different reproduction of colors , as shown opposite . Some people find that they prefer the colors given by one brand to another . But the differences are unavoid- able , so if you want to make a series of pictures , keep to the same film type , or at least to the same manufacturer .
When using color film , try to choose lighting that will keep the exposure times within the range 1 / 1000–1 second . Owing to reciprocity failure ( see p . 107 ) films not only respond to very long or very short exposures as if they had a slower speed rating , but often alter their color balance , distorting the color reproduction .
Before and after use store all unprocessed color film in cool , dry conditions .
The structure of color film
Gelatin supercoat
Blue sensitive layer
Yellow filter layer
Green sensitive layer
Red sensitive layer
Film base with anti - halation dye
Anti - curl backing
Color film consists of three per- manently coated layers of black and white emulsion , carefully bal- anced in speed and contrast , and one filter layer . The top emulsion is sensitive only to blue light- similar to the blue - only color sen- sitivity of bromide paper . Below this , a yellow filter layer prevents blue light from penetrating further .. The second emulsion layer is sensi- tive to green light . The third layer is sensitive to red . The film base and backing are the same as in black and white film ( see p . 125 ) .
All four layers collectively measure less than 001 mm thick . Together they can encode all the colors of an image , each color or tone giving a different combination of responses in the three emulsion layers . White or neutral gray gives an equal response throughout .
In most film , dye - forming com- pounds are present in each emul- sion layer . These combine with the processing chemicals to develop three separate image layers , each in a different color ( the yellow filter becomes colorless ) . The changes . which occur in each layer during processing to form a full color image are shown on pages 162-3 .
Slide and print systems
Color slide film given color reversal processing produces positive color images on the film . Each image can be mounted separately in plas- tic or card frames , and projected or hand - viewed .
Color negative film is processed to form negatives . These can be enlarged and printed on to color photographic paper . The negatives appear orange , because of a dye arrangement which reduces con- trast and improves the color accu- racy of the print .
The procedures for making prints from color slides , slides from color negatives , and black and white prints from both types of film , are shown on pages 172-5 .
Over- and underexposure
To measure exposure for color film . you can generally use the same methods you have found success- ful in black and white work ( see pp . 39-43 and 104-7 ) . But there are some characteristic differences between negative and slide films .
Underexposing slide film results in a dark image , near right , particu- larly in the shadows . Overexposure gives a pale image , far right . par- ticularly in the highlights . In prac- tice , a slightly dark transparency is usually more acceptable than one which looks washed out , so underexposure is preferable to overexposure with color slide film .
Underexposing color negative film gives a thin image , near right , and overexposing produces a dense result . far right .
The orange mask on the nega- tives makes them appear darker than they really are , so check very carefully for the presence of shadow detail . Because the negatives are an intermediate stage , general ad- justment of density is possible dur- ing printing , providing sufficient detail exists in the image . Thin color negatives seldom print well so you should overexpose rather than underexpose .
Differences in color reproduction
Even with accurate exposure and the correct light source , different brands of film give slightly different color reproduction , particularly on slide film . This is largely due to : differences in chemical dyes .
The films shown here are , from left to right . Kodachrome . Fuji- chrome , and Agfachrome . Varia- tions between them are much more noticeable in neutral tones or pale , skin colors than in strong colors . You will find that some brands may give a slightly more pleasant reproduction of reds and yellows . others of greens and blues .
STEP 1 : COLOR FILM / Types and structure
There are two main factors to consider when choosing color film . First , the form you want your result to take - slide , print , or perhaps both . And second , the lighting you will be using to take the pictures . Different types of film must be used under daylight and tungsten ( artificial ) lighting .
Modern color films produce either slides ( color transparencies ) or color negatives ( for color prints ) . Black and white prints can be obtained from both types of film . The final form of your image is not fixed by the film you use . You can obtain slides from negatives , or prints from slides ( see pp . 172- 5 ) . But the best all - round results are achiev- ed when you use the film that gives you the final form you want transparencies or prints . A third type of color film - instant picture film is discussed on page 210 .
Color slide film
Slide film , also called reversal film , is given a processing sequence which forms positive images directly on the film taken from the camera . These transparencies can either be projected on to a screen or looked at in a hand viewer . You can process most color slide films , such as Ektachrome and Agfa- chrome , yourself , as explained on page 164 . A few types , such as Kodachrome , have a particular chemical structure which means that the processing must be done by the manufacturers or their agents .
Using color slide film has several advan- tages . You can do your own processing without a darkroom or any special equip- ment . Color slides , shown on a good pro- jector in a blacked out room , give images . that are unrivalled for fine detail , brilliance , and accuracy of color . Another consider- ation in favor of color slide film is that in terms of cost per picture , slides are the cheapest form of color photography .
Color negative film
All color negative films can be home pro- cessed . In processing , they follow a simpler sequence of stages than slide film to produce an image with negative tone values and complementary ( or " opposite " ) colors . Like a black and white negative , this is an inter- mediate form from which positive prints can be made on photographic paper for which you require a darkroom . You will need much of the equipment used in black and white printing , shown in the larger dark- room on page 74 .
Unlike color slide film , negatives allow you to lighten or darken the image during . printing , and adjust the colors by filtering . Color prints are a convenient form for your pictures , and you can make many prints from the same negative .
Daylight and tungsten film
Each layer is sensitive to one of the three primary colors - blue , green , and red - from which all other colors are composed . The sensitivity of all three emulsion layers of the film is carefully " balanced " to record and reproduce colors and tones acceptably .
Most color films are balanced for subjects lit by daylight . Tungsten lighting produces slightly more red and less blue wavelengths than daylight . This is not normally notice- able because our eyes quickly adapt when changing from outdoor daylight to tungsten lit , indoor surroundings . Unlike our eyes color film is fixed in its response . Con- sequently , daylight balanced films give results with a strong orange cast if the sub- ject is in tungsten light . If you use a film balanced for tungsten lighting in daylight conditions , the results will appear blue .
If you are using color negative film with the wrong light source , you can , to some extent , correct for this when printing . But this should be avoided as the heavy filtering required often obstructs other , more subtle color controls .
For the best results use daylight and tungsten films only in the lighting for which they are intended . Try to avoid subjects lit by a mixture of daylight and tungsten light unless noticeable differences in color are part of the effect you want . On page 146 you can see how to use correction filters with tungsten or daylight film to compensate for incorrect lighting .
Speed and brand
The speed ratings of color films for general photography range from 25 ASA ( Koda- chrome ) , the slowest , to 400 ASA ( Koda- color and Fujicolor ) , the fastest color film available . As in black and white photo- graphy , the appearance of fine detail deterio- rates and grain becomes more noticeable with faster film . In extreme cases , particu- larly when very fast film is overdeveloped , tiny irregular globules of color can be seen in enlargements . For maximum resolution of detail , you should use the slowest film that lighting conditions will allow .
Each make and brand of color film gives slightly different reproduction of colors , as shown opposite . Some people find that they prefer the colors given by one brand to another . But the differences are unavoid- able , so if you want to make a series of pictures , keep to the same film type , or at least to the same manufacturer .
When using color film , try to choose lighting that will keep the exposure times within the range 1 / 1000–1 second . Owing to reciprocity failure ( see p . 107 ) films not only respond to very long or very short exposures as if they had a slower speed rating , but often alter their color balance , distorting the color reproduction .
Before and after use store all unprocessed color film in cool , dry conditions .
The structure of color film
Gelatin supercoat
Blue sensitive layer
Yellow filter layer
Green sensitive layer
Red sensitive layer
Film base with anti - halation dye
Anti - curl backing
Color film consists of three per- manently coated layers of black and white emulsion , carefully bal- anced in speed and contrast , and one filter layer . The top emulsion is sensitive only to blue light- similar to the blue - only color sen- sitivity of bromide paper . Below this , a yellow filter layer prevents blue light from penetrating further .. The second emulsion layer is sensi- tive to green light . The third layer is sensitive to red . The film base and backing are the same as in black and white film ( see p . 125 ) .
All four layers collectively measure less than 001 mm thick . Together they can encode all the colors of an image , each color or tone giving a different combination of responses in the three emulsion layers . White or neutral gray gives an equal response throughout .
In most film , dye - forming com- pounds are present in each emul- sion layer . These combine with the processing chemicals to develop three separate image layers , each in a different color ( the yellow filter becomes colorless ) . The changes . which occur in each layer during processing to form a full color image are shown on pages 162-3 .
Slide and print systems
Color slide film given color reversal processing produces positive color images on the film . Each image can be mounted separately in plas- tic or card frames , and projected or hand - viewed .
Color negative film is processed to form negatives . These can be enlarged and printed on to color photographic paper . The negatives appear orange , because of a dye arrangement which reduces con- trast and improves the color accu- racy of the print .
The procedures for making prints from color slides , slides from color negatives , and black and white prints from both types of film , are shown on pages 172-5 .
Over- and underexposure
To measure exposure for color film . you can generally use the same methods you have found success- ful in black and white work ( see pp . 39-43 and 104-7 ) . But there are some characteristic differences between negative and slide films .
Underexposing slide film results in a dark image , near right , particu- larly in the shadows . Overexposure gives a pale image , far right . par- ticularly in the highlights . In prac- tice , a slightly dark transparency is usually more acceptable than one which looks washed out , so underexposure is preferable to overexposure with color slide film .
Underexposing color negative film gives a thin image , near right , and overexposing produces a dense result . far right .
The orange mask on the nega- tives makes them appear darker than they really are , so check very carefully for the presence of shadow detail . Because the negatives are an intermediate stage , general ad- justment of density is possible dur- ing printing , providing sufficient detail exists in the image . Thin color negatives seldom print well so you should overexpose rather than underexpose .
Differences in color reproduction
Even with accurate exposure and the correct light source , different brands of film give slightly different color reproduction , particularly on slide film . This is largely due to : differences in chemical dyes .
The films shown here are , from left to right . Kodachrome . Fuji- chrome , and Agfachrome . Varia- tions between them are much more noticeable in neutral tones or pale , skin colors than in strong colors . You will find that some brands may give a slightly more pleasant reproduction of reds and yellows . others of greens and blues .
تعليق