copied with a film, such as Kodak Commercial film. An
original with a weak, faded image should be copied with
a film, such as Kodak Contrast Process Ortho.
SPECIAL APPLICATIONS IN COPYING
Special applications are used in copying to detect
information that cannot be seen with our eyes under
normal lighting conditions. Because these are special
applications, they are not performed in most Navy
imaging facilities, but are still worth mentioning. These
methods involve the use of infrared and ultraviolet
radiation and special types of films.
Black-and-White Infrared
Copying with black-and-white infrared films and
infrared radiation can help in deciphering old, charred,
or altered documents. This is possible because similar
appearing materials can reflect and transmit invisible
infrared radiation in different amounts. For example,
two ink signatures may appear identical to the eye.
However, when photographed with an infrared film, the
two signatures may appear totally different.
A suitable infrared filter must be used when
black-and-white infrared films are exposed. This is
because infrared film is sensitive to visible light as well
as infrared radiation. The infrared filter absorbs the
visible light so the film image is produced entirely with
infrared radiation. For specific filter recommendations,
consult the data supplied with the film or the Photo-Lab
Index.
Infrared wavelengths are longer than visible light
wavelengths and do not focus on the same plane as
visible light. Therefore, a slight increase in lens-to-film
distance is necessary. A separate focusing scale for
infrared is indicated on the focusing scale of most lenses.
Ultraviolet Radiation
Copying with ultraviolet (UV) radiation can aid in
detecting chemically erased or badly faded writing and
restoration or alteration of artwork because different
materials reflect or fluoresce different amounts of
ultraviolet radiation.
Photographing with reflected ultraviolet radiation
in total darkness is possible because some of the
ultraviolet absorbed by a material may be overlooked as
visible light or fluorescence. Such photography in
darkness is possible only when a material is illuminated
with an ultraviolet source, such as the General Electric
Uviarc. The fluorescence from a material illuminated
with ultraviolet radiation should be photographed with
a No. 2A (pale yellow) filter to absorb the stronger UV
reflections. A recommended film to use for ultraviolet
photography is Kodak Contrast Process Ortho film.
Exposure tests should be conducted to determine the
best exposure for an ultraviolet copy setup.
Do not use commercial ultraviolet lamps in which
the lamp itself is an ultraviolet filter. These lamps
transmit visible light that does not permit photographing
a fluorescing original.
COPYING REFLECTION ORIGINALS
Reflection originals are documents or other flat
objects like pictures or drawings that are viewed and
photographed (copied) by reflected light.
Copying reflection originals can be done with either
horizontal or vertical copy cameras or setups. The size
of the copy setup can range from the space necessary to
attach the original to a wall and make the copy photo
with a tripod-mounted camera, to a copy setup which
fills two rooms- one containing the camera back and
darkroom and the other the copyboard. Regardless of
the different copy setups possible for reflection
originals, the copying techniques are the same with few
exceptions. In general, the procedures used for copy
work are placing the original on the copyboard, aligning
the optical axis of the lens with the original, lighting the
original, focusing the lens, calculating the exposure, and
exposing the film.
PLACING THE ORIGINAL ON
THE COPYBOARD
A copyboard should have a positive means of
attaching and holding the original. The means of
attaching the original could be spring clips, small bar
magnets, thumbtacks or pushpins, a hinged glass frame,
a sheet of glass, vacuum, and so forth. When thumbtacks
or pushpins are used, be sure not to punch holes in the
original. For high volume copy, a vacuum copyboard
allows a more rapid change and positioning of originals
on the copyboard.
When you are using a vertical copy camera or setup,
a darkroom printing easel may be used to hold the
original in place.
ALIGNING THE OPTICAL AXIS OF THE
LENS WITH THE ORIGINAL
Arising, falling, and sliding front feature of a copy
camera provides for the alignment of the lens and the
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