Improvements in the Method of and in Cameras for Producing Photographic Pictures.
Year: 1898

page_text: Date of Application, 14th Nov., 1898- Accepted, 21st Jan., 1899
VUMI --- 47
Improvements in the Method of and in Cameras for Producing
Photographic Pictures.
I, CHARLES ANTHONY BURGHARDT, of 35, Fountain Street, Manchester, in the
County of Lancaster, Analytical Chemist, and late Lecturer in Mineralogy in
the Victoria University, Manchester, do hereby declare the nature of this inven-
tion and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement and accompanying drawings.
-
My said invention relates to an improved method of and means for producing
photographic pictures and has for its object to produce photographs which shall
render more naturally the object to be pictured.
As is well known, photographs obtained by the medium of a single lens have
a lack of relief and do not truly represent what the eyes of the spectator see.
This has been sought to be overcome by means of stereoscopic photography in
which two separate prints from a negative taken with twin lenses are observed
through a stereoscope.
The prints coalesce and the various objects in the pictures are seen to stand out
in relief. The effects thus produced however are far from natural. The various
objects it is true are observed in different planes but they have a lack of solidity
as if cut sharply out of some flat material and have a very unnatural look to
the eye.
The object of my invention is to obtain a single picture which shall have all
the relief and true effect of a landscape or other object visible to the eye, without
the use of the stereoscope.
This I effect by means of a camera provided with two lenses of similar foci,
and projecting the image from each lens upon a mirror mounted to swivel at any
angle to the axis of the lens. The image from each mirror is diverted upon an-
other mirror and from thence to a common screen, upon which the pictures from
the right and left hand lenses are absolutely combined.
By substituting a sensitised plate in place of the screen a negative of the object
can be obtained.
And in order that my invention may be fully understood I will now describe
the same with reference to the accompanying diagrams.
Fig. 1 is a diagramatic representation in sectional plan showing the combined
image of two lenses projected upon a sensitised surface arranged at the back of
the camera.
Fig. 2 is an elevation of the arrangement of mirrors.
Fig. 3 is a modification of my invention.
The camera is provided with lenses a a of equal foci disposed a suitable dis-
tance apart as in stereoscopic photography, say from 3 to 3 inches measuring
from the centres of the lenses. I provide a suitable frame to which the mirrors
are secured. This frame consists of an upper and lower board b b (see Fig. 2)
secured permanently together by means of angle pieces cc (Fig. 1).

page_text: The angle pieces c c are arranged at an angle of 45 degrees as shown in the
sectional plan Fig. 1 and to these angle pieces I glue, cement or otherwise
suitably secure two mirrors d d.
Between the boards bb I also mount to swivel loosely two carriers e e provided
with mirrors ff. The mirrors are of plain silvered glass the thinnest procur-
able. I have obtained the best results with glass or about 2 of an inch thick
and arranged with the silvered surface at the back. The silver is thus protected
and the glass being of such thinness double reflection is obviated.
The focussing, screen or sensitised surface is represented at g. The mirrors d f
are arranged at such angles that the incident rays h from the lenses a and the
reflected rays from the mirrors d f coalesce upon the focussing screen or sen-
sitised plate g and form a compound image.
This is conveniently effected as follows.
The frame carrying the arrangement of mirrors is disposed in position within
the camera behind the lens board.
In hand cameras of the box type the frame might be permanently fixed, and
with folding or collapsible cameras the frame could be conveniently hooked or
otherwise temporarily secured in position at the back of the lens board.
The image from a pre-determined test object by means of one lens only is
first reflected from the movable mirror f upon the fixed mirror d and from thence
upon the focussing screen until the required sharpness of detail is obtained. The
lenses a a being of equal foci and mounted upon the same lens board it follows
that the focussing of one lens suffices for the other.
The other lens is then uncapped and the mirrors f f are turned upon their
pivots ff until the required angle at which both images coalesce is obtained.
The mirrors ff are then secured at this angle by means of the milled nuts f
and are always in position to produce the requisite compound image from the
two lenses. The size of picture obtained will vary according to the foci of the
lenses employed. I have found in practice that by the use of lenses of 8 inch
equivalent foci with the arrangement of mirrors shown in Figs. 1 and 2 that a
picture of the popular quarter plate size (4 inch x 3 inch) can be produced.
The proper angles of the mirrors f f having been once determined for objects
distant say 20 feet to infinity from the lenses no further manipulation of the
mirrors is required for landscape work or for objects not in close proximity to
the camera. For portraiture or still life where a great extension of the camera
bellows is necessary the angle of the movable mirrors f f may need re-adjusting.
This can be readily effected by slackening the nuts f³. In cameras of the box
type or in any case where the mirror frame is permanently fixed to the back of
the lens board the pivots f¹ f¹ may be carried through the camera case so that
the mirrors may be manipulated from the outside and be secured at the proper
angles by suitable nuts.
In Fig. 3 I show a modification of my invention.
In this arrangement the incident rays h from the lenses a a are reflected by
mirrors pivotted at 11 to the camera case or a suitable frame, upon a fixed mirror
k secured to the mirror frame or it might be to the back of the lens board and
from thence to the focussing screen l. With this arrangement pictures of com-
paratively small size only can be obtained and I therefore prefer the arrangement
shown in Figs. 1 and 2.
The method of determining the correct angle of the mirrors jj is as already
described and when such correct angle has been attained the mirrors are per-
manently or temporarily secured at this angle.
When the object has been correctly focussed upon the screen / a sensitised
plate or film is introduced to obtain the requisite negative.
Although I prefer to mount the reflecting mirrors within a suitable frame as
described, if desired where space permits the mirrors may be mounted within 5
the camera body.
Photographic prints obtained by my method possess truthfulness to nature in

page_text: a very high degree, showing the relief and delicate gradation of light and shade
observed by the eye in the object itself and which it is impossible to obtain with
a print from a negative taken with one lens.
Thus it is possible by means of a single print from the compound image borne
by the negative, to obtain without the aid of extraneous apparatus, an accurate
rendering of the subject whether landscape, figure or architectural, to correspond
with that seen by the eye when viewing the original.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is:-
(1) The improved means for obtaining negatives for the production of photo-
graphic prints consisting of the fixed mirrors d d and movable mirrors f f of
thin silvered glass by which a compound image from two lenses of equal foci can
be reflected upon the sensitive surface of the plate or film for the purpose and
substantially as described and illustrated in Figs. 1 and 2 of the drawings.
(2) The modified arrangement shown in Fig. 3 of the drawings consisting of
the movable mirrors reflecting the incident rays of the lenses upon a fixed
mirror from which it is reflected upon the sensitised surface, the mirrors being
made of thin silvered glass, in the manner and substantially as described and
shown.
Dated this 12th day of November 1898.
For the Applicant,
E. K. DUTTON & Co.,
Chartered Patent Agents, 5, John Dalton Street, Manchester.