(4) The silver is then bleached from the paper and the dye images
remain. The three dye images alter and reflect the light used to view the
print so that a full color positive image of the original scene is noticed.
b. Silver-Dye Bleach Process.
Another way to make full color prints
directly from color transparencies is by the silver-dye bleach process (also
called the dye destruction color process). The only direct positive color
materials currently manufactured which employ this process are Cibachrome
products. This process will be discussed in part B of this lesson.
c. Principles Used.
The principles of making color positive prints
from color transparencies are the same whether coupler development or dye
destruction materials. You use colored filters to alter the printing light
to obtain proper color balance much the same as in printing color negatives.
3.
Equipment.
Reversal color paper is exposed with enlargers designed for printing color
negatives.
a. Using the Enlarger. The enlarger should be equipped to hold color
printing or color compensating filters, or to use dial-in filtrations such
as dichroic filters.
Various reversal papers have different requirements
for ultraviolet and infrared cutoff filters.
Consult the data sheets
accompanying the different papers to determine these requirements.
b. Placing the Filter.
Place an infrared cutoff filter in a
perpendicular position to the enlarger's optical axis and close to the light
source in a specular, parallel part of the light beam. If light is passed
through the IR cutoff filter at an angle, changes to the spectral quality of
the filter will result.
c. Voltage Regulation. Voltage regulation for the enlarger is just as
important in printing color slides as for printing color negatives.
Therefore, use a voltage regulator.
Some color enlargers which have
tungsten-halogen lamps have a built-in stepdown transformer which acts like
a voltage regulator.
4.
Making the First Test Print.
For making your first color print on reversal paper, you should select a
transparency that has been correctly exposed with light of the correct color
quality and intensity. This will become your "standard transparency." This
standard transparency should be on the same kind of film you regularly use.
Even better, make several standard transparencies on the different color
5-3
SS0514
Previous Page
