320
9.
PHOTOGRAPHY
board will suffice, or even the edge of one's hand. Angles can be made
simply with two pieces of overlapping cardboard, or hands one on top
of the other, or even the thumb extended away from the palm. If a central area of the image requires additional exposure, this can be achieved
with a piece of cardboard having a hole in it, or even by letting a beam
of light pass between overlapped fingers. It is desirable to have in the
darkroom a few masks of different shapes that can be handily used as
needed.
Although print control by dodging is an art important to electron
microscopists, unnecessary dodging wastes time, effort, and paper. If
enough care is taken in making the original electron micrographs, dodging should not ordinarily be required. The commonest reason for having
to dodge a print is carelessness in making the negative in the first place.
In the excitement of focusing and adjusting the microscope to take a
picture, it is all too easy to forget to be sure that there is even illumination across the area to be photographed. The image is particularly apt
to be unevenly illuminated when one is working at high magnification
with a close to cross-over beam. Rarely is the adage that "an ounce of
prevention is worth a pound of cure" more applicable!
One other trick of print control has occasional usefulness. If a small
portion of a print has been slightly underexposed, it may be "intensified"
while in the developing bath by a little heat applied locally. This can
be done by soaking the hands in the developer, and then squeezing the
underexposed portion of the print between the palms so that close contact is made. Thirty to 60 seconds of body heat will darken the image
somewhat, perhaps just enough to save the print. More intensification
can be obtained if quite hot water from a hose is played over the pale
areas for a few seconds while the print is still soaked with developer. Or
the heat may be applied from a wrung-out piece of sponge or a wad of
cotton. Comparable local intensification of moderate degree may also
be achieved by swabbing areas with undiluted developer, or warm
developer.
9.11. Problem Negatives, Reduction and Intensification
Overexposed negatives can be saved if the overexposure is not too
extreme. Any one of the standard "proportional" photographic reducers
can and should be used. It is desirable to reduce them rather than to
try very long printing exposures. If the negative density is such that a
9.
PHOTOGRAPHY
board will suffice, or even the edge of one's hand. Angles can be made
simply with two pieces of overlapping cardboard, or hands one on top
of the other, or even the thumb extended away from the palm. If a central area of the image requires additional exposure, this can be achieved
with a piece of cardboard having a hole in it, or even by letting a beam
of light pass between overlapped fingers. It is desirable to have in the
darkroom a few masks of different shapes that can be handily used as
needed.
Although print control by dodging is an art important to electron
microscopists, unnecessary dodging wastes time, effort, and paper. If
enough care is taken in making the original electron micrographs, dodging should not ordinarily be required. The commonest reason for having
to dodge a print is carelessness in making the negative in the first place.
In the excitement of focusing and adjusting the microscope to take a
picture, it is all too easy to forget to be sure that there is even illumination across the area to be photographed. The image is particularly apt
to be unevenly illuminated when one is working at high magnification
with a close to cross-over beam. Rarely is the adage that "an ounce of
prevention is worth a pound of cure" more applicable!
One other trick of print control has occasional usefulness. If a small
portion of a print has been slightly underexposed, it may be "intensified"
while in the developing bath by a little heat applied locally. This can
be done by soaking the hands in the developer, and then squeezing the
underexposed portion of the print between the palms so that close contact is made. Thirty to 60 seconds of body heat will darken the image
somewhat, perhaps just enough to save the print. More intensification
can be obtained if quite hot water from a hose is played over the pale
areas for a few seconds while the print is still soaked with developer. Or
the heat may be applied from a wrung-out piece of sponge or a wad of
cotton. Comparable local intensification of moderate degree may also
be achieved by swabbing areas with undiluted developer, or warm
developer.
9.11. Problem Negatives, Reduction and Intensification
Overexposed negatives can be saved if the overexposure is not too
extreme. Any one of the standard "proportional" photographic reducers
can and should be used. It is desirable to reduce them rather than to
try very long printing exposures. If the negative density is such that a