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9.
PHOTOGRAPHY
in the negative. At the other end of the tonal scale, an enlarging paper of
suitable contrast should be chosen so that only limited areas, lines, etc.,
should be totally black in a properly exposed print.
The light source of the enlarger preferably should be spread over the
negative by suitable condenser lenses rather than relying upon diffusion
plates (or be a fluorescent source). In practice a "condenser type" enlarger produces an image with superior contrast, equivalent to about
one contrast grade of paper. This is an important advantage.
9.9. Timing Print Exposures
As the previous section has indicated, it is essential that prints be fully
developed if they are to have the quality that comes from a full range of
tonal values. This in turn means that the enlarging paper must be properly exposed in the first place. There are electronic aids which can help
determine the correct exposure (discussed below). These, however, are
expensive and not generally found in darkrooms. Also, their use requires
interpretation on the basis of knowledge, so that they hardly help the
beginner. Most investigators will continue to use their eyes and judgment
in estimating proper exposure time. The beginner will certainly waste a
good deal of photographic paper. This will be the cost of his education.
Every possible effort should be made to standardize the exposure. One
has a choice of using a relatively dim image and long exposure, or a bright
image and a short exposure. There are good reasons for deciding upon
a fairly long exposure, perhaps 30 seconds. The "stopped down" lens
then will have excellent depth of focus. This also gives time for the manipulation of the image by "dodging" as discussed below. The eye can
estimate the required image intensity fairly accurately in this range. With
ordinary types of enlarging papers there is just enough illumination to
visualize the image faintly. If the first exposure proves slightly incorrect,
7-10 seconds can be added or subtracted with considerable accuracy, and
produce just the right exposure. On the other hand, short exposures are
harder to judge and afford little time for image manipulation.
The different contrast grades of enlarging papers require somewhat
different exposures, the "soft" papers less than the "hard" ones. Therefore, one should make an effort to standardize illumination so that the
most commonly used grade of paper is exposed for, let us say, 30 seconds.
If the next softer grade of paper is used, about 7 seconds will have to be
9.
PHOTOGRAPHY
in the negative. At the other end of the tonal scale, an enlarging paper of
suitable contrast should be chosen so that only limited areas, lines, etc.,
should be totally black in a properly exposed print.
The light source of the enlarger preferably should be spread over the
negative by suitable condenser lenses rather than relying upon diffusion
plates (or be a fluorescent source). In practice a "condenser type" enlarger produces an image with superior contrast, equivalent to about
one contrast grade of paper. This is an important advantage.
9.9. Timing Print Exposures
As the previous section has indicated, it is essential that prints be fully
developed if they are to have the quality that comes from a full range of
tonal values. This in turn means that the enlarging paper must be properly exposed in the first place. There are electronic aids which can help
determine the correct exposure (discussed below). These, however, are
expensive and not generally found in darkrooms. Also, their use requires
interpretation on the basis of knowledge, so that they hardly help the
beginner. Most investigators will continue to use their eyes and judgment
in estimating proper exposure time. The beginner will certainly waste a
good deal of photographic paper. This will be the cost of his education.
Every possible effort should be made to standardize the exposure. One
has a choice of using a relatively dim image and long exposure, or a bright
image and a short exposure. There are good reasons for deciding upon
a fairly long exposure, perhaps 30 seconds. The "stopped down" lens
then will have excellent depth of focus. This also gives time for the manipulation of the image by "dodging" as discussed below. The eye can
estimate the required image intensity fairly accurately in this range. With
ordinary types of enlarging papers there is just enough illumination to
visualize the image faintly. If the first exposure proves slightly incorrect,
7-10 seconds can be added or subtracted with considerable accuracy, and
produce just the right exposure. On the other hand, short exposures are
harder to judge and afford little time for image manipulation.
The different contrast grades of enlarging papers require somewhat
different exposures, the "soft" papers less than the "hard" ones. Therefore, one should make an effort to standardize illumination so that the
most commonly used grade of paper is exposed for, let us say, 30 seconds.
If the next softer grade of paper is used, about 7 seconds will have to be