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معالجة الألوان والطباعة .. المرشد خطوة بخطوة للتصوير الفوتوغرافي
COLOR PROCESSING AND PRINTING
STEP 1 : How color films work
STEP 2 : Color film processing
STEP 3 : Color printing
STEP 4 : Converting prints and slides STEP 5 : Finishing prints and slides
Color processing and printing uses many of the procedures introduced in black and white work , but it does require extra care and attention to details . You need to control very accurately the temperatures of solutions and the times they are allowed to act to get consistently good results . Very little more equipment is required than you have already used for black and white processing and printing . But the materials films , chemicals , and paper are more expensive than for black and white work .
Although this may sound frightening , you will in fact find color printing one of the most stimulating and creative areas of darkroom work . Since in many ways it is easier to do than simply read about , work through each stage as you read , perhaps using a trial pack of paper and minimum quantities of chemicals . Before you can start you should already be doing your own black and white processing and printing , as well as having read and worked through the section on color photography . In fact , we assume that you will have read through most of the earlier part of the book , and already have a fair amount of darkroom experience in processing and printing .
The Steps in Color Processing and Printing are sequential and concentrated . So work through them in order , taking your time , and mastering each stage before moving on . Get into the habit of making notes , on details such as times and filter settings , particularly when color printing . Later , when judging tests for example , you will want to refer back to these for details of filter settings and exposure times .
The first part of this section deals with film processing . As in black and white processing , you do not require a darkroom , but you will need more solutions and greater control of their temperatures . You can begin by processing your own films , leaving color darkroom work until later . If you are using color slide film this will give you finished results . But if you want to tackle color printing you will almost certainly be using color negatives and it is possible to leave the routine processing of these to a commercial laboratory .
A few slide films , such as Kodachrome , cannot be home processed . They are known as " non - substantive " types and require long and complicated processing which is only practical on automatic machinery . You have to send them to the manufacturer or their agents for processing . Usually the cost is already included in the price of the film . But the great majority of slide films and color negative films can be user processed . Each type , and often each brand , follows its own particular processing sequence and requires its own kit of processing chemicals . But gradually greater uniformity in method and solutions is being introduced . Eventually there may be only two kits - one for color slide films and one for color negative films and papers . This is still in the future , so you must always check that your film and the process you are using are compatible .
The basic principles shown here are well established and still apply , but check the manufacturer's instructions with your processing kit for current temperatures and times . Generally you will find that all color processes tend to use higher solution temperatures than their black and white equivalents .
Compatibility between materials is not so essential in color printing , when selecting brand of color negative and the paper to print it on . Provided the color paper is designed for printing from negatives you can , for example , print Kodak negatives on Agfa paper . However , to begin with stick to one brand of film and paper . The contrast and the color rendering of each paper is designed to match the manufacturer's negatives , so you will not be faced with such complicated juggling of the color balance in the print . Do not try printing one make of film on to a different make of paper until you are more experienced . Then , you may find that the slightly different rendering of some colors ( like the differences in slide films shown on page 145 ) suits some subjects .
For color processing and printing you can use your black and white film developing tank ( see p.69 ) , and probably your enlarger . Most enlargers either have a filter drawer or a color dial - in head for color printing . A filter drawer is cheaper , but a dial - in head is easiest to use . The most expensive new item of equipment you will require is a daylight developing drum for prints . You can use several trays instead , but a drum makes the job of processing prints so much more convenient that it should almost be considered essential .
The organization of the section
The first Step in this section explains how color films work - the changes that have to be made within the three emulsion layers ( see p.144 ) , sensitive to blue , green , and red , to reproduce the colors in the original image .
From the three primaries you can make up any other color in the color circle . But instead of these primary colors , all modern films and papers use complementary colored dyes to reproduce the subject . These are the three colors that are opposite to the primaries on the color circle , as shown on page 148. A complementary color absorbs light of the primary color opposite it , and passes the remaining light , that is , light of the other two primaries . Yellow dye , for example , absorbs light of its opposite , primary color - blue , but allows the two other primaries - red and green - to pass . Similarly , magenta absorbs green and passes blue and red , and cyan absorbs red and passes blue and green .
Since yellow , magenta , and cyan absorb about one third of the spectrum each , they can be used superimposed together to create colored images . Primary colors absorb two thirds of the color spectrum and only pass their own color . Consequently they could not be used in film or paper to produce an image , because the top layer would block colors present in the two lower layers . Color processing therefore produces a complementary colored
image in each layer . In a color slide , for example , the top layer is made yellow wherever blue was not present in the subject . The yellow dye image stops unwanted blue light , but without interfering with the green and red sensitive layers ( magenta and cyan ) below . The diagram on page 162 shows how an image is built up in this way .
Color negatives also use yellow , magenta , and cyan dye images . Since it is a negative image the colors are reversed yellow appears where blue was actually present , magenta where green was present , and so on . The image is complementary in tone and color to the original subject . Color paper has three similar layers of emulsion so that when the negative is enlarged on to it , and processed , it gives a positive , correct color print .
First color photograph
In 1861 James Clerk - Maxwell produced the first natural color photograph , above , to demonstrate the additive three - color principle . He used three separate plates , exposed through a red , green , and blue filter
respectively . Then he projected each with light of the same color as the filter , and superimposed the images . ( Clerk - Maxwell's red plate was not in fact red sensitive it was later discovered that it recorded ultra- violet light reflected from red areas . )
Color triangles
Remembering the color triangle relationships shown left will help you understand the principles of color processing and printing . The three primary colors which together make up white light are shown in the solid line triangle . Their respective complementary colors are directly opposite them , in the three apexes of the dotted line triangle .
Yellow , magenta , cyan
Each complementary color is a mixture of the two primaries it does not absorb . Overlapping filters , when held up to white light , right , show how other colors are formed by using the three complementaries alone . Notice how , where two complemen- taries overlap , the one common primary color is allowed to pass .
How dyes affect light
As shown below , left , deep blue . green , and red dyes each absorb two- thirds of the spectrum from white light . The layers in film and paper are sensitive to these colors but after processing form three negative toned images of the subject in the complementary colors yellow . magenta , and cyan . As you can see . below right , each of these subtract from white light only one primary color . Each color passes two thirds of the spectrum so that the three colors sandwiched together in film or paper give a full color result .
Color film processing
Different chemicals and more processing stages are required for color slide films than for color negatives because you produce a final color positive on the film itself . It takes about 30 minutes excluding washing ; color negative film takes about 17 minutes . Most color slide films can be " pushed " or " held back " by altering the time given for the first processing stage . This compensates for up or down - rating the ASA speed , respectively , during exposure . However , doubling or halving the speed is about the maximum you can expect without creating some unwanted side - effects . These include loss of subtle tones of color , producing grays on the image instead of blacks , or an overall color cast . Don't try adjusting the development time of color negative film - the resulting negative may look fine but often proves impossible to print , with shadows giving one tint and highlights another .
You will find that the main challenge in film processing - in fact all color processing - is to maintain temperatures and times with the greatest possible accuracy . Manufacturers warn that most developer stages have to be held within 1 ° F ( 0.1 ° C ) of the specified temperature . If the temperature is a few degrees in either direction your results will usually be acceptable , but when you compare your films you will notice the color variation .
Color printing
In the next Step - color printing from color negatives - there are two alternative ways of working . The cheapest , but crudest method is to give the paper three separate exposures to the image through three filters - deep blue , green , and red . This is like exposing each emulsion layer of the paper separately . By varying the three exposure times you control the respective color in your print . This " additive " system sounds simple but it is very time- consuming and you will find that controlling the density and color on the print by shading and printing - in is impossible . So we have followed the more popular , " subtractive " exposing method for color printing .
Subtractive printing uses yellow , magenta , and cyan filters in varying strengths to tint the enlarger light source . In this way you control the amounts of blue , green , and red light which reach the color paper and affect each of its layers . Only one exposure is needed , and it is easier to control the image than with the " additive " method .
Practice at color printing is very important . You must get used to judging both the density and color in the print , and deciding by how much filters should be changed to give the exact result you need . The best way to give yourself experience is to make a " ring- around " set of prints like the one on page 167 , using one of your own , correctly exposed color negatives .
Once you can successfully make " straightforward " prints you can begin introducing the local controls . These include shading or printing - in through filters to correct or alter the color in different parts of the image . Pages 170-1 show you some of the more interpretative effects possible , such as printing black and white negatives through filters on to color paper . Even color photograms are possible . There is no reason why your color printing should always aim for a faithful accuracy to subject colors . Try experimenting fully - this will improve your technical expertise and understanding of color printing , and may open up new areas for creative ideas .
If you prefer working with slides , or have a large collection of slides , you can make color prints from them by reversal , or positive - from - positive printing . This involves enlarging the color slide on to a reversal printing material , which is then given a special reversal processing . In theory this system is very convenient , although some reversal papers do require six processing stages . In practice the quality , especially from contrasty slides , is not as good as from an original color negative . Improvements are still being made in reversal printing and this might eventually become the most popular way of working . It has the advantage of allowing you to project your color pictures as well as having them as prints . Some manufacturers offer trial kits of reversal paper and chemicals , and since you only require your color enlarger and developing drum to do reversal printing you can easily try out this system for yourself .
You can also make black and white prints and color slides from color negatives . In fact whether you start from a color slide or color negative you can adapt the final result into another form . The diagram on page 172 summarizes the various methods of converting your final image .
Color print retouching and mounting follows a routine similar to black and white retouching and mounting ( see pp.88 , 138- 40 ) . You can , for example , texture the print surface , following a similar method as for black and white prints ( see p.139 ) . Page 176 explains some of the corrections you can make to color prints and the more minor modifications you can make to slides .
Do not display your color prints in strong sunlight . Most print dyes are not very resistant to fading . Reversal print materials such as Cibachrome are much more permanent , but no color image , print or slide , will survive long exposure to brilliant light without some change in the colors occurring . Slides always look best when projected information on different projectors is shown on page 212 .
COLOR PROCESSING AND PRINTING
STEP 1 : How color films work
STEP 2 : Color film processing
STEP 3 : Color printing
STEP 4 : Converting prints and slides STEP 5 : Finishing prints and slides
Color processing and printing uses many of the procedures introduced in black and white work , but it does require extra care and attention to details . You need to control very accurately the temperatures of solutions and the times they are allowed to act to get consistently good results . Very little more equipment is required than you have already used for black and white processing and printing . But the materials films , chemicals , and paper are more expensive than for black and white work .
Although this may sound frightening , you will in fact find color printing one of the most stimulating and creative areas of darkroom work . Since in many ways it is easier to do than simply read about , work through each stage as you read , perhaps using a trial pack of paper and minimum quantities of chemicals . Before you can start you should already be doing your own black and white processing and printing , as well as having read and worked through the section on color photography . In fact , we assume that you will have read through most of the earlier part of the book , and already have a fair amount of darkroom experience in processing and printing .
The Steps in Color Processing and Printing are sequential and concentrated . So work through them in order , taking your time , and mastering each stage before moving on . Get into the habit of making notes , on details such as times and filter settings , particularly when color printing . Later , when judging tests for example , you will want to refer back to these for details of filter settings and exposure times .
The first part of this section deals with film processing . As in black and white processing , you do not require a darkroom , but you will need more solutions and greater control of their temperatures . You can begin by processing your own films , leaving color darkroom work until later . If you are using color slide film this will give you finished results . But if you want to tackle color printing you will almost certainly be using color negatives and it is possible to leave the routine processing of these to a commercial laboratory .
A few slide films , such as Kodachrome , cannot be home processed . They are known as " non - substantive " types and require long and complicated processing which is only practical on automatic machinery . You have to send them to the manufacturer or their agents for processing . Usually the cost is already included in the price of the film . But the great majority of slide films and color negative films can be user processed . Each type , and often each brand , follows its own particular processing sequence and requires its own kit of processing chemicals . But gradually greater uniformity in method and solutions is being introduced . Eventually there may be only two kits - one for color slide films and one for color negative films and papers . This is still in the future , so you must always check that your film and the process you are using are compatible .
The basic principles shown here are well established and still apply , but check the manufacturer's instructions with your processing kit for current temperatures and times . Generally you will find that all color processes tend to use higher solution temperatures than their black and white equivalents .
Compatibility between materials is not so essential in color printing , when selecting brand of color negative and the paper to print it on . Provided the color paper is designed for printing from negatives you can , for example , print Kodak negatives on Agfa paper . However , to begin with stick to one brand of film and paper . The contrast and the color rendering of each paper is designed to match the manufacturer's negatives , so you will not be faced with such complicated juggling of the color balance in the print . Do not try printing one make of film on to a different make of paper until you are more experienced . Then , you may find that the slightly different rendering of some colors ( like the differences in slide films shown on page 145 ) suits some subjects .
For color processing and printing you can use your black and white film developing tank ( see p.69 ) , and probably your enlarger . Most enlargers either have a filter drawer or a color dial - in head for color printing . A filter drawer is cheaper , but a dial - in head is easiest to use . The most expensive new item of equipment you will require is a daylight developing drum for prints . You can use several trays instead , but a drum makes the job of processing prints so much more convenient that it should almost be considered essential .
The organization of the section
The first Step in this section explains how color films work - the changes that have to be made within the three emulsion layers ( see p.144 ) , sensitive to blue , green , and red , to reproduce the colors in the original image .
From the three primaries you can make up any other color in the color circle . But instead of these primary colors , all modern films and papers use complementary colored dyes to reproduce the subject . These are the three colors that are opposite to the primaries on the color circle , as shown on page 148. A complementary color absorbs light of the primary color opposite it , and passes the remaining light , that is , light of the other two primaries . Yellow dye , for example , absorbs light of its opposite , primary color - blue , but allows the two other primaries - red and green - to pass . Similarly , magenta absorbs green and passes blue and red , and cyan absorbs red and passes blue and green .
Since yellow , magenta , and cyan absorb about one third of the spectrum each , they can be used superimposed together to create colored images . Primary colors absorb two thirds of the color spectrum and only pass their own color . Consequently they could not be used in film or paper to produce an image , because the top layer would block colors present in the two lower layers . Color processing therefore produces a complementary colored
image in each layer . In a color slide , for example , the top layer is made yellow wherever blue was not present in the subject . The yellow dye image stops unwanted blue light , but without interfering with the green and red sensitive layers ( magenta and cyan ) below . The diagram on page 162 shows how an image is built up in this way .
Color negatives also use yellow , magenta , and cyan dye images . Since it is a negative image the colors are reversed yellow appears where blue was actually present , magenta where green was present , and so on . The image is complementary in tone and color to the original subject . Color paper has three similar layers of emulsion so that when the negative is enlarged on to it , and processed , it gives a positive , correct color print .
First color photograph
In 1861 James Clerk - Maxwell produced the first natural color photograph , above , to demonstrate the additive three - color principle . He used three separate plates , exposed through a red , green , and blue filter
respectively . Then he projected each with light of the same color as the filter , and superimposed the images . ( Clerk - Maxwell's red plate was not in fact red sensitive it was later discovered that it recorded ultra- violet light reflected from red areas . )
Color triangles
Remembering the color triangle relationships shown left will help you understand the principles of color processing and printing . The three primary colors which together make up white light are shown in the solid line triangle . Their respective complementary colors are directly opposite them , in the three apexes of the dotted line triangle .
Yellow , magenta , cyan
Each complementary color is a mixture of the two primaries it does not absorb . Overlapping filters , when held up to white light , right , show how other colors are formed by using the three complementaries alone . Notice how , where two complemen- taries overlap , the one common primary color is allowed to pass .
How dyes affect light
As shown below , left , deep blue . green , and red dyes each absorb two- thirds of the spectrum from white light . The layers in film and paper are sensitive to these colors but after processing form three negative toned images of the subject in the complementary colors yellow . magenta , and cyan . As you can see . below right , each of these subtract from white light only one primary color . Each color passes two thirds of the spectrum so that the three colors sandwiched together in film or paper give a full color result .
Color film processing
Different chemicals and more processing stages are required for color slide films than for color negatives because you produce a final color positive on the film itself . It takes about 30 minutes excluding washing ; color negative film takes about 17 minutes . Most color slide films can be " pushed " or " held back " by altering the time given for the first processing stage . This compensates for up or down - rating the ASA speed , respectively , during exposure . However , doubling or halving the speed is about the maximum you can expect without creating some unwanted side - effects . These include loss of subtle tones of color , producing grays on the image instead of blacks , or an overall color cast . Don't try adjusting the development time of color negative film - the resulting negative may look fine but often proves impossible to print , with shadows giving one tint and highlights another .
You will find that the main challenge in film processing - in fact all color processing - is to maintain temperatures and times with the greatest possible accuracy . Manufacturers warn that most developer stages have to be held within 1 ° F ( 0.1 ° C ) of the specified temperature . If the temperature is a few degrees in either direction your results will usually be acceptable , but when you compare your films you will notice the color variation .
Color printing
In the next Step - color printing from color negatives - there are two alternative ways of working . The cheapest , but crudest method is to give the paper three separate exposures to the image through three filters - deep blue , green , and red . This is like exposing each emulsion layer of the paper separately . By varying the three exposure times you control the respective color in your print . This " additive " system sounds simple but it is very time- consuming and you will find that controlling the density and color on the print by shading and printing - in is impossible . So we have followed the more popular , " subtractive " exposing method for color printing .
Subtractive printing uses yellow , magenta , and cyan filters in varying strengths to tint the enlarger light source . In this way you control the amounts of blue , green , and red light which reach the color paper and affect each of its layers . Only one exposure is needed , and it is easier to control the image than with the " additive " method .
Practice at color printing is very important . You must get used to judging both the density and color in the print , and deciding by how much filters should be changed to give the exact result you need . The best way to give yourself experience is to make a " ring- around " set of prints like the one on page 167 , using one of your own , correctly exposed color negatives .
Once you can successfully make " straightforward " prints you can begin introducing the local controls . These include shading or printing - in through filters to correct or alter the color in different parts of the image . Pages 170-1 show you some of the more interpretative effects possible , such as printing black and white negatives through filters on to color paper . Even color photograms are possible . There is no reason why your color printing should always aim for a faithful accuracy to subject colors . Try experimenting fully - this will improve your technical expertise and understanding of color printing , and may open up new areas for creative ideas .
If you prefer working with slides , or have a large collection of slides , you can make color prints from them by reversal , or positive - from - positive printing . This involves enlarging the color slide on to a reversal printing material , which is then given a special reversal processing . In theory this system is very convenient , although some reversal papers do require six processing stages . In practice the quality , especially from contrasty slides , is not as good as from an original color negative . Improvements are still being made in reversal printing and this might eventually become the most popular way of working . It has the advantage of allowing you to project your color pictures as well as having them as prints . Some manufacturers offer trial kits of reversal paper and chemicals , and since you only require your color enlarger and developing drum to do reversal printing you can easily try out this system for yourself .
You can also make black and white prints and color slides from color negatives . In fact whether you start from a color slide or color negative you can adapt the final result into another form . The diagram on page 172 summarizes the various methods of converting your final image .
Color print retouching and mounting follows a routine similar to black and white retouching and mounting ( see pp.88 , 138- 40 ) . You can , for example , texture the print surface , following a similar method as for black and white prints ( see p.139 ) . Page 176 explains some of the corrections you can make to color prints and the more minor modifications you can make to slides .
Do not display your color prints in strong sunlight . Most print dyes are not very resistant to fading . Reversal print materials such as Cibachrome are much more permanent , but no color image , print or slide , will survive long exposure to brilliant light without some change in the colors occurring . Slides always look best when projected information on different projectors is shown on page 212 .
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