AN IMPROVED MODE OF OBTAINING PHOTOGRAPHIC NEGATIVES OR POSITIVES, AND APPARATUS THFREFOR,
Year: 1885

page_text: We, JAMES ROBERTSON, and DOUGLASS ROBERTSON both of 109 Kenmure Street,
East Pollokshields, in the County of Renfiew, Photographers, do hereby declare the
nature of our Invention for "AN IMPROVED MODE OF OBTAINING PHOTOGRAPHIC
NEGATIVES OR POSITIVES, AND APPARATUS THFREFOR, and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement
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"
Our Invention relates to the lighting and shading of the surfaces of objects in
relief, for obtaining photographic negatives or positives, for producing the corre-
sponding photographic images, in relievo oi in intaglio by printing from, by any of
the photographic relief printing processes, such as the bichromate and gelatine
process or similar well known processes
To produce photographic images in relievo or in intaglio, it is important that the
light and shade, or the dense and clear portions on the finished negative, should
correspond with the relief on the object photographed, that those parts highest in
relief and the other parts in their proportion, should be the densest or clearest on
the finished negative, at will. This object we attain by our Invention which
consists in placing the object to be photographed in a studio or enclosed space, and
lighting the object from the sides and top or surrounding it by a parallel beam or
beams of coloured light, which may be any suitable coloured artificial light, or sun-
light transmitted through coloured glass, coloured fabric, or other coloured trans
parent or translucent medium We let fall or project in front of the object, a
parallel beam of actinic light, which may be any artificial actinic light or sunlight
directed at or nearly at right angles to the surrounding top and side beams of
coloured light, so as to penetrate the coloured beams of light surrounding the
object. The depth of coloured light used should depend on the strength or quality
of actinic light, thus the stronger the front beam of actinic light used, the deeper
the coloured light should be. The parallel beam of actinic light 18 directed through
a movable screen or tunnel which is opaque at the sides top and bottom One end
of the screen is placed in front of the object to be photographed, and during
exposure of the plate in the camera it is traversed over the object to be photo-
graphed, cutting off in a sharp line or a diffused line, the surrounding side and top
beams of coloured light, beginning with those parts of the object highest in relief or

page_text: nearest the camera, and finishing with those parts lowest in relief or furthest away
from the camera The use of the parallel beam or beams of coloured light
surrounding the object to be photographed, is to prevent the parallel beam of
actinic light in front, which enters at the mouth and pisses through the movable
screen or tunnel from penetrating and illuminating the object too quickly As the
screen or tunnel traverses over the object, it cuts off the surrounding side and top
beams of coloured light, allowing the parallel beams of actinic light from the front
to fall first on those parts of the object highest in relief or nearest, and in turn
those parts lowest in relief or furthest away By regulating and varying the
duration of the lights, by the movable screen or tunnel the desired different
densities on the negatives can be obtained, so that those parts of the object highest
in relief or nearest the camera desired to be densest on the negative shall be longest
exposed to the actinic light, and those parts of the object lowest in relief or furthest
away from the camera desired to be the clearest, shall receive the shortest exposure
to the actinic light The movement of the screen or tunnel may be effected direct
by hand, or by any suitable mechanical apparatus, such as a weight, retaided in its
descent by a small fan, like that used in clockwork
By printing in any of the photographic relief printing processes such as the
bichromate and gelatine process or similar processes, from negatives or positives
obtained in the manner described, we obtain moulds, casts, or dies of portraits in
relief or raised designs suitable for moulding from in plastic substances or for
electrotyping, relief stamping or embossing purposes. One mode of obtaining the
relief from our negatives or positives which we find to answer well consists in
coating glass plates with the following solutions, viz, 1 ounce of gelatine dissolved
in 10 ounces of water, when dissolved adding 40 grains of bichromate of potassium
and a few drops of glycerine The prepared plates when set are soaked in a trough
of cold water to dissolve out part of the bichromate out of the upper surfaces of the
films, so that the film side next the glass will be more sensitive when the light gets
weakest. The prepared plates when dry are printed in contact with our negatives
or positives, and afterwards when printed soaked in cold water, and those parts the
most acted on by the light will be the least absorbent and will swell the least, and
those parts least acted on by the light will be the most absorbent and swell the
Moulds, casts, or dies may be made from these films in any plastic sub-
stances, stucco, gutta-percha or electrotypes may be taken from the films
most
In the accompanying drawings, Figure 1 is a plan, Figure 2 is a side sectional
elevation, and Figure 3 is an end sectional elevation of a photographic studio or
operating room, the back portion A in which the object B to be photographed is
placed being portioned off or shut off from the front part C by an opaque screen or
wall D The back portion A is lighted up with coloured -beams of light from the
side walls E, E, by panes of glass E¹, El, and from the roof F, F, by panes of
glass F', F'.
The camera G is placed in the front part of the studio C, and actinic light is
admitted to the front part C from the end wall H by the panes of glass H, H, and
in front of and between the camera G and the object B to be photographed.
Through the opaque screen or wall D is fitted a movable screen or tunnel I which
18 opaque on the sides top and bottom, and through the open ends of the screen or
tunnel I the actinic light from the panes H¹, H¹, in the end wall H has free access
to the object to be photographed and pierces into the coloured light in the back
part of the studio A The movable screen or tunnel I is moved past the opaque
screen or wall D, and over the object to be photographed during the exposure of
the plate in the camera G, by the cords J, J, passing over the pulleys K, K, by a
weight L retarded in its descent by the fan M, varying speeds as may be wished
being obtained by the use of proportional weights.
Figure 4 is a plan similar to Figure 1 but shows the movable screen or tunnel I
moved down past the screen or wall D and cutting off the coloured light in the
back part A from the nearest points on the object to be photographed to the
camera G, and the actinic light which passes down inside the movable screen or

page_text: tunnel I taking the place of the coloured light on the nearest points on the
object B instead.
Figure 5 is an end sectional elevation through the front part of the studio C, and
shows the object B to be photographed as seen looking through the tunnel I
Figure 6 is a plan and Figure 7 is an end sectional elevation of an ordinary
photographic studio or operating room, the portion of the studio A in which the
object B to be photographed is placed being screened off from the studio C on the
sides by the light portable screens E E, and on the top by the screens F, the back
part A being lighted by coloured light from the panes of glass or transparent media
in the side screens E, E, and the top screen Fat E, E, and F, as shown by the
surrounding radial lines E, E¹, and F, round the object B in Figure 7
The camera G is placed in the studio C and in front of and between the camera G
and the object to be photographed, and set through the opaque ends D of the side
and top screens E, E, and F is a movable screen or tunnel I opaque on the sides,
top, and bottom, and through the open ends of the screen or tunnel I the actinic
light in the studio C is reflected up or otherwise has free access to the object B and
pierces the coloured light in the back part A
The movable screen or tunnel I is moved down past the object to be photographed
during exposure of the plate in the camera G, by preference beginning at the opaque
ends D of the side screens E, E, and top screen F, and moving forward over the
object B and finishing at the line I, or beginning at the line I and over the
object B finishing at the ends D of the side screens E E and top screens F,
the screen being moved by the cords J, J, passing over the pulleys K K by a
weight L retarded in its descent by the fan M as shown on the before described
Figure 2
Having now particularly described and ascertained the nature of our said
Invention and in what manner the same is to be performed, we declare that what
we claim is
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First The mode herein described of "exposing' or illuminating objects to be
photographed, said mode consisting in directing on the object from the front,
parallel rays or beams of actinic light, and from the sides rays of coloured light or
light of less actinic power, substantially as set forth
Second. The mode herein described of obtaining photographic negatives or
positives for printing from in relief or in intaglio, said mode consisting in exposing
the object to be photographed to illumination by parallel rays of actinic light in
front, and by rays of coloured light at the sides or sides and top, such coloured rays
being gradually cut off during the exposure of the plate substantially as set forth
Third The arrangement in a photographic studio or operating room of a movable
tunnel or screen adapted to transmit parallel rays of light on to an object, and by
its movement to gradually cut-off from the object the light admitted from the sides
and top substantially as described and illustrated
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