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الطباعة العكسية - عملية تدمير الصبغة .. معالجة الألوان والطباعة .. المرشد خطوة بخطوة للتصوير الفوتوغرافي
Reversal printing- dye destruction process
Dye destruction print materials , such as Cibachrome , have color dyes already built into the three emulsion layers , instead of forming the dyes chemically during pro- cessing . The top layer , sensitive to blue , incorporates yellow dye ; the green sensitive layer has magenta dye ; and the bottom , red layer contains cyan dye .
Only three solutions are required to pro- cess dye destruction materials . The prints have brilliant well - saturated colors , more resistant to fading than conventional color images . This is because the three com- plementary colored dyes are not created during processing and have been manu- factured for their purity and permanence .
The bleach solution is very acidic , so it is essential to wear gloves when mixing or handling the chemical . Kits contain neutra- lizing chemicals that should be added to the used bleach before throwing it away . The whole process takes 12 minutes and should be carried out at 75 ° F ( 24 ° C ) , with a toler- ance of plus or minus 3 ° F ( 1 · 75 ° C ) .
The Cibachrome process
The Cibachrome developer turns the three latent images in the com- plementary colored layers into black silver negatives .
Original transparency
Black and white ( Cibachrome ) development
Bleach
Final print
The bleach destroys the black silver and dye images in the nega- tives , leaving three complementary colored positives . Together these make up the final image .
Cibachrome processing
In complete darkness load the exposed print , emulsion side in- ward , into the developing drum . Replace the drum lid and turn on normal lighting .
1. Put on the rubber gloves and check that the temperature of the developer is about 75 ° F ( 24 ° C ) . Pour in the developer , then follow the kit recommendation for agita- tion . Typical development time is two minutes .
Begin draining the drum into a pail about 15 seconds before the end of development time .
2. Return the drum to the water bath . Check the temperature of the bleach . If it is within the recommended range , add it to the drum and start the timer . Bleaching takes four minutes . Once again start draining the chemical 15 seconds before the end of the time . Pour the bleach into the pail and add the neut- ralizing chemicals .
3. Make sure that the temperature of the fixer is correct , then pour it into the drum . Start the timer - fixing takes three minutes - and agitate the solution for the full time . Pour away the fixer .
Take off the rubber gloves and carefully remove the print from the drum . Wash the print for three minutes in a resin - coated print washer . Follow any of the methods used for resin - coated papers to dry the print .
Assessing exposure and filtration
As with ordinary color prints , the exposure and filtration should be assessed from two separate tests .
For the first test strip , to assess exposure , set the filters as suggest- ed by the print material manufact- urers to suit your brand of slide film . Then make a series of doub- ling exposures across the paper . Process and check the results .
From the most accurately ex- posed band on the first test strip you can judge the filtration . Re- move or add filters accordingly , referring to the table on page 173 . Using likely filter settings , make a filtration test following the method shown on page 166 .
In general filter changes pro- duce much smaller alterations to colors than in negative / positive printing . Correcting color casts on slides therefore calls for quite large changes in the filter values .
Reversal printing- dye destruction process
Dye destruction print materials , such as Cibachrome , have color dyes already built into the three emulsion layers , instead of forming the dyes chemically during pro- cessing . The top layer , sensitive to blue , incorporates yellow dye ; the green sensitive layer has magenta dye ; and the bottom , red layer contains cyan dye .
Only three solutions are required to pro- cess dye destruction materials . The prints have brilliant well - saturated colors , more resistant to fading than conventional color images . This is because the three com- plementary colored dyes are not created during processing and have been manu- factured for their purity and permanence .
The bleach solution is very acidic , so it is essential to wear gloves when mixing or handling the chemical . Kits contain neutra- lizing chemicals that should be added to the used bleach before throwing it away . The whole process takes 12 minutes and should be carried out at 75 ° F ( 24 ° C ) , with a toler- ance of plus or minus 3 ° F ( 1 · 75 ° C ) .
The Cibachrome process
The Cibachrome developer turns the three latent images in the com- plementary colored layers into black silver negatives .
Original transparency
Black and white ( Cibachrome ) development
Bleach
Final print
The bleach destroys the black silver and dye images in the nega- tives , leaving three complementary colored positives . Together these make up the final image .
Cibachrome processing
In complete darkness load the exposed print , emulsion side in- ward , into the developing drum . Replace the drum lid and turn on normal lighting .
1. Put on the rubber gloves and check that the temperature of the developer is about 75 ° F ( 24 ° C ) . Pour in the developer , then follow the kit recommendation for agita- tion . Typical development time is two minutes .
Begin draining the drum into a pail about 15 seconds before the end of development time .
2. Return the drum to the water bath . Check the temperature of the bleach . If it is within the recommended range , add it to the drum and start the timer . Bleaching takes four minutes . Once again start draining the chemical 15 seconds before the end of the time . Pour the bleach into the pail and add the neut- ralizing chemicals .
3. Make sure that the temperature of the fixer is correct , then pour it into the drum . Start the timer - fixing takes three minutes - and agitate the solution for the full time . Pour away the fixer .
Take off the rubber gloves and carefully remove the print from the drum . Wash the print for three minutes in a resin - coated print washer . Follow any of the methods used for resin - coated papers to dry the print .
Assessing exposure and filtration
As with ordinary color prints , the exposure and filtration should be assessed from two separate tests .
For the first test strip , to assess exposure , set the filters as suggest- ed by the print material manufact- urers to suit your brand of slide film . Then make a series of doub- ling exposures across the paper . Process and check the results .
From the most accurately ex- posed band on the first test strip you can judge the filtration . Re- move or add filters accordingly , referring to the table on page 173 . Using likely filter settings , make a filtration test following the method shown on page 166 .
In general filter changes pro- duce much smaller alterations to colors than in negative / positive printing . Correcting color casts on slides therefore calls for quite large changes in the filter values .
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