[mprovements in the Method of and Means for Modelling by the Aid of Photography.
Year: 1891

page_text: COMPLETE SPECIFICATION.
[mprovements in the Method of and Means for Modelling by the Aid
of Photography.
I, HERMANN PÖTSCHKE of 4 Bergmannstrasse in the Kingdom of Prussia and
German Empire, Photographer, do hereby declare the nature of this invention, and
n what manner the same is to be performed, to be particularly described and ascer-
ained in and by the following statement:-
This invention relates to a method of and means for modelling by the aid of
photography either on a reduced or enlarged scale or to the natural size, and which
s generally applicable to all objects which may be conveniently photographed as
hereinafter described, but is more particularly intended for the modelling or
production of portrait busts.
I will describe my improvements with reference to the accompanying diagram-
(1) TAKING THE PHOTOGRAPHIC NEGATIVES.
It will be assumed that it is desired to model the portrait bust of an individual.
If we imagine a series of vertical planes each passing through the vertical axis of
the head of this individual, each of these planes will divide the surface of the head
and bust of the person into two equal parts. If again, we assume each of the
planes to be non-reflecting and opaque and a strong light to be exhibited on one
side, it will be evident that only the lighted part can be photographed. If then,
successive planes be employed in successive longitudes, or if the sitter be rotated
through successive angles in the same plane, a series of photographic silhouettes
may be obtained covering the whole surface of the head and bust of the sitter.
In practice either of the arrangements represented by Figures 2 and 3 be
employed, these figures being in plan.
Figure 1 is an elevation of the arrangement illustrated by Figure 2.
may
The source of light B is arranged level with the head of the sitter. As near as
it can be conveniently arranged to the sitter, there is fixed a vertical opaque
screen CD, at a right angle to the line joining the light with the vertical axis A A
of the sitter, so as to shut off all rays of light from one half of his head and bust.
By this means that part of the sitter. which is on one side of the vertical plane
passing through the source of light B and the vertical axis will be illuminated,
whilst that part on the other side will be dark. By turning the seat on which the
individual is seated, or by moving the source of light and the screen, it is possible
to illuminate any desired half of the sitter and thus to obtain a series of photographs
comprising the whole surface of the head and bust.
The photographic camera E is arranged at the same level as the source of light
and the head of the sitter and with its axis in a line which cuts the vertical axis A A
and forms an angle a of less than 90 degrees, as shewn by Figure 2. By this
arrangement it is possible to obtain clear photographic outlines of those parts which
might be otherwise in shadow, as for example below such projecting parts as the
eyebrows and nose. Starting with the profile successive photographs are taken,
With the described
preferably by an instantaneous process, right round the sitter.

page_text: arrangement of the camera, the photographs would be foreshortened, and to obtain
the proper proportions, either the arrangement indicated in Figure 2 or that in
Figure 3. may be employed. As illustrated by Figure 2 the sensitised plate m n is
held in the camera at an angle a to its axis this angle being the same as the angle
included between the lines joining the source of light and the camera respectively
with the vertical axis A A. Alternatively, the arrangement illustrated by Figure 3
may be employed, in which case the sensitised plate is held in the camera in the
ordinary manner. As shown by this figure, a vertical mirror G H is arranged at
the angle a to the vertical plane cutting the source of light and the vertical
axis AA and the camera is arranged with its axis parallel with that vertical
plane and pointing to a spot on the mirror at a right angle to the axis of the
sitter.
The negatives must be taken in a chamber the floors walls and roof of which are
non-reflecting.
In order to secure the axis of the head of the sitter in the vertical line A A, a
flat horizonral ring or head rest F is employed. By means of radial studs or
adjusting screws in the ring, the head may be brought into the exact desired
position and fixed there. It is preferred to employ a rotating chair, and it is more
convenient to rotate the sitter than the source of light, screen, and photographic
apparatus.
During the intervals which separate the taking of the negatives, the chair and
sitter are turned through a certain number of degrees each time, until the number
of exposures required for the whole circumference have been made. The number
of degrees or the angles through which the sitter has been successively turned must
be carefully noted, as this information is subsequently necessary in arranging the
silhouettes together. A similar result is obviously obtainable by keeping the
sitter stationary and successively moving the whole of the apparatus around him
through the whole circumference, or separate sources of light, separate screens,
and separate cameras, may be employed for each exposure; but in all cases
each exposure should be numbered and the angle between it and the previous
ex xposure noted.
The hair eyebrows beard and moustache should be powdered with flour or white
powder before the exposures are made, particularly in the case of persons with dark
hair.
(2) THE PREPARATION OF THE SILHOUETTES.
Photographic copies or positives are taken from the negatives on thin sensitised
sheets of metal, such as copper, the sensitised surface being formed upon an etching
ground or varnish. The outlines of the silhouettes are traced through the etching
ground with a needle or graving point and are then etched through, thus separating
the silhouette from the rest of the plate. The head rest or ring F which is
photographed in each negative must be left upon each silhouette as an horizontal
strip which becomes of service when the silhouettes are arranged together in the
following operation.
(3) COMPOSING THE SILHOUETTES.
This operation requires a suitable frame which consists of a vertical cylindrical
core and an upper and a lower horizontal ring. The core and rings have formed in
them vertical radial slits at exactly the same angles as those at which the various
negatives were originated in the photographic process. The silhouettes are
arranged in this frame in their proper order, with the horizontal strips (i.e. the
photographs of the head rest F) which have been left on them fixed to the upper
ring. The back edges of the silhouettes, which represent the vertical axis A A are
brought together at the axis of the core of the frame. Thus a radial skeleton out-
line is obtained, which represents the outline of the head and bust by means of a
number of meridian like lines formed by the front edges of the silhouettes, and this
1.

page_text: outline is in exact accordance with the reality. Between the silhouettes angular
spaces are left which have now to be filled up.
(4) FILLING IN THE INTERMEDIATE SPACES.
The angular spaces which are left between the silhouettes are now filled in with
modeller's clay, wax, or other plastic material, starting from the core or centre.
By gradually filling it from the centre all round, the silhouettes become gradually
fixed, so that the supporting rings may soon be cut away leaving the modeller
unobstructed in his work.
For the face which requires much greater care to secure the proper expression,
the angles at which the successive negatives are taken should be much smaller than
for the remainder of the work. The larger the number of silhouettes taken, the
more easy will be the subsequent modelling and the more accurate the final result.
An expert modeller will be required for the finishing touches.
The portrait bust thus modelled may be reproduced in the usual manner.
In the foregoing description, reference has been made only to the production of
portrait busts, but other objects may be similarly reproduced by the same means
and in the same manner, and more particularly sculpture and similar works. The
process is especially adapted for reproducing suitable works of art on a reduced or
enlarged scale.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is,
1. The hereinbefore described method of modelling by the aid of photography,
substantially as and by the means set forth.
2. In the process of modelling by the aid of photography, taking a series of
negatives from different points of the person or object to be modelled the person or
object being partly lighted and partly in deep shadow, and the camera being
arranged in each case to take a sharp photograph of the line dividing the light from
the shadow without foreshortening; substantially as herein before described.
3. In the process of modelling by the aid of photography, producing silhouettes
in sheet metal or similar material by photographic printing and etching, from the
negatives produced as described in the preceding clause; substantially as herein-
before described.
4. In the process of modelling by the aid of photography, arranging the sil-
houettes produced as set forth in the preceding claiming clause, radially around a
central core and filling up the spaces between them with suitable plastic material;
substantially as herein before described.
5. Silhouettes for modelling by the aid of photography, produced as herein before
described and having a projection corresponding with the head rest or ring for the
purpose of serving as an index or datum in arranging the silhouettes; substantially
as hereinbefore described.
Dated this 30th dox of December AD 1891