(1) Negative masking to correct dye error.
Color masks, which
provide a neutralizing effect for unwanted dye absorption, are readily seen
in the unexposed areas of a color negative (figure 2-2). There are two such
masks: a yellow mask in the green-sensitive (magenta dye-forming) layer, and
a reddish magenta mask in the red (cyan dye-forming) layer. Together, they
produce an orange tint in unexposed areas.
There is no need to mask the
blue-sensitive (yellow dye-producing) layer since the yellow dyes usually
have negligible unwanted dye absorption.
Figure 2-2.
Negative color masking
(2) How masks work. The absorption of a mask corresponds to that of
the dye layer for which it is made. For example, magenta dye (which should
absorb only green) absorbs blue light.
The yellow mask for this layer
absorbs the same amount of blue light uniformly over the area of the
negative, except where magenta dye is produced. Thus, where magenta dye is
produced, the yellow mask is destroyed in an equal proportion. The result
is elimination of color distortion because the unwanted absorption is
uniform over the entire negative area. This is done by using a colored dye
coupler. An ingredient (quinone diimine) in the color developer reacts with
this coupler to form magenta dye and destroys the yellow coupler. The red
coupler for the cyan-dye layer works in the same manner.
The mask forms
automatically during color development and remains in the film after
processing.
(3) Results of not masking. If you do not mask, two types of errors
will occur in reproduction. These errors are in the saturation and hue of
colors. Blues, cyans, and greens tend to be too dark, while reds, oranges,
and yellows tend to be too light.
Second, hue-shift errors occur.
Reds
usually shift toward orange, magentas toward red, and cyans and greens
toward blue.
2-4
SS0514
Previous Page
