Improvements in or relating to the Production and Exhibition of Photographic Representations in Natural Colours.
Year: 1899

page_text: Improvements in or relating to the Production and Exhibition of
Photographic Representations in Natural Colours.
A communication from Louis Decos DU HACRON, Chemical Engineer, of Saint-
Maurice, near Paris, in the Republic of France.
I, ALFRED JULIUS BOULT, of 111, Hatton Garden, in the County of London,
Chartered Patent Agent, do hereby declare the nature of this invention to be
as follows:-
This invention relates to an apparatus by the aid of which the operation of
the light taking place and manifesting itself in the dark upon the photographic
plate, when the ordinary operative method is employed, will automatically pro-
duce a view of the object in its original colours in the said apparatus, without
a fresh operation being necessitated.
Two principles serve as a basis for the construction of the device which will
now be described.
1. That of reversing the direction in which the luminous rays travel.
2. That by virtue of which an object reflected by the two opposite faces of a
non-plated (or unsilvered) glass plate, ceases to present double outlines, if between
the glass plate and the object a convergent leus is interposed, in the principal-
focus of which the object is placed, and this irrespective of what may be the
focal length; the effect of the lens being to place the object optically at infinity;
inversely, the same lens has the property of forming in its principal focus a
non-doubled image of a distant object reflected by the non-plated (or unsilvered)
glass plate.
The apparatus consists of a box or casing composed of two parts; one is
divided by two partitions, forming three spaces, into which the luminous rays
enter through three convergent lenses, of one and the same focal length, and
arranged rigidly upon the vertical wall, separating the two parts of the appara-
tus; these lenses may be simply ordinary non-achromatic lenses; and they
may be of circular or rectangular form, as described.
The second part comprises an opening for the admission of luminous rays for
taking the photograph or negative or for the admission of the visual rays, when
one observes the positive triple-photograph.
Below this opening are arranged, at an angle of 45 degrees, three glass-plates,
two of which are non-plated (or unsilvered) whilst the third and lowest is
silvered.
At the end of the camera part of the apparatus, and facing the partition, a
frame is placed, in which are arranged: a blue-violet screen, corresponding to
the top unsilvered glass plate, a green screen, corresponding to the other un-
silvered glass plate, and a red-orange screen corresponding to the silvered glass
plate. Behind this frame a sensitized pan-achromatic or orthochromatic plate

page_text: is placed, which is arranged in a frame or holder at the principal focus of the
lenses, and on which plate are received the impressions of the images respec-
tively passing through the screens.
Above the opening a removable support is placed on which is mounted at an
angle of 45 degrees, a mirror serving to reflect the images to be photographed;
this mirror which is only provided on the apparatus for the purpose of taking
the photograph, can be replaced by a prism with total reflection. Upon the front
of the apparatus a convergent lens of comparatively great focal length is placed
which serves as a ".
magnifier or focussing lens. The same is thus used only
at the moment of taking the photograph, and only in case where the object to
be reproduced lies very near, its object being then to transport it optically, to
infinity. A lens very slightly concave and serving as the eye piece is applied
when the triple-image is to be observed, and has for its object to render the
view of the latter very clear. It is preferably covered with a diaphragm the
small opening of which occupies exactly the optical centre of the apparatus.
The rays reflected by the mirror traverse the diaphragm in the opening, then
are divided into three bundles; the first is reflected by the first unsilvered glass
plate traverses its lens, then the blue-violet screen and forms the top image;
the second is reflected by the second unsilvered glass plate, traverses its lens
then the green screen and forms the second and middle image; the third which
is the strongest is reflected by the silvered glass plate, traverses its lens then
the red-orange screen and forms the third image. The red-orange light, being
the least actinically active of the three lights transmitted by the different screens.
necessitates the use of a silvered glass plate which, reflecting almost the whole
of the ray it receives, reduces the exposure required for the third image to that
of the second. In order to control the action of the blue-violet light, which
would require an exposure of much less duration for the first image than for
the two others, upon the opening (only for the time of exposure) is placed a
green transparent screw which freely transmits only the green and red rays,
but the centre of which is pierced with a narrow opening transmitting, as far
as the blue-violet light is concerned, only sufficient light to form the corres-
ponding image, during the same time of exposure as the two other parts of the
apparatus. Under these conditions the equilibrium between the three images
would not be perfect in the case of panchromatic plates being used; the image
formed by the green light would appear with a slight delay; a very simple
remedy for which consists in covering the second unsilvered glass plate with a
second unsilvered glass plate in perfect contact therewith. The two glass plates
are connected together say by means of strips of paper, pasted over their edges.
Great care must be taken not to cement the two glass plates together over their
active surfaces; otherwise the two supplementary reflections which are required
would be destroyed.
When the triple negative or chromogram is obtained a positive is made by
contact upon opal glass or upon polished glass, using preferably a special plate
for positives and this triple positive is placed in a frame arranged on the ap-
paratus, in the same position that the frame carrying the negative plate occu-
pied during the exposure care being taken that each of the three positives occu-
pies the position which the negative, furnishing the same, formerly occupied,
and that the colour screens are on their part maintained in their respective
places; only the gelatine layer or film must be placed upward and not below
as during exposure of the negative. Upon the bottom of the apparatus a frame
is applied formed of a plate, in which three openings corresponding to the three
positive images are provided; in one of them, a transparent membrane screw or
film of a somewhat dark grey is placed, the object of which is to moderate the
brilliancy of the third image, illuminated by the red-orange screw and re-
flected by the silvered glass plate. The frame or support carrying the eye piece
of slight divergency is then put in place. This last frame should be black or
of a dark colour and should extend sufficiently in width in order that the eye

page_text: which does not look into the apparatus may remain open without affecting the
clear vision of the other eye.
The instrument being appropriately inclined toward the light, if the eye is
applied against the opening of the diaphragm one observes in the direction of
the mirrors an amplified polychromatic image, being the synthetical result from
the combination or fusion of the three black positives, one illuminated by red-
orange light, the second by green and the other by blue-violet. This image
appears identical-not only as regards colour but as regards perspective and
the erection of lines-to the photographed object, as if latter were presented to
the eye placed in the centre of the diaphragm. The image is entirely free
from aberration, from refrangibility and from distorsion, notwithstanding the
use of non-achromatic lenses, and the arrangement of the latter at large and
unequal distances from the diaphragm. This general correction is due to the
fact that the rays, in returning from the three images to the eye, through the
combination of lenses and reflectors, follow exactly the same path which they
had traversed originally.
If it is desired to increase the field or angle of view, which is naturally and
strictly limited according to the construction of the apparatus all that is neces-
sary is to arrange over the opening a small tube provided at each end with a
lens; the one in front being divergent and the one at the back convergent, the
The whole combina-
focus of the former being shorter than that of the second.
tion thereof constitutes an inverted Galileo lens, and possesses two properties:
1. That of collecting and concentrating in the field occupied by each of the
three images upon the plate, a larger portion of the horizon; 2. That, inversely
to the former, of exhibiting during the observation of the triple image in the
apparatus, this same portion under the real angle of magnification. This small
supplementary objective permits of dispensing with the "focussing lens
well as the lens of slight divergence which serves as the eye piece all that is
necessary is to adjust the two constituent lenses to a slight extent relatively to
each other, until the correct focus is obtained.
"
as
On this objective the different diaphragms as well as the yellow perforated
circular screen are adjusted.
According to the law of reversion of the direction of luminous rays, the sym-
metrical and mathematically correct arrangement of the three internal mirrors
and of the three lenses is by no means necessary for the separate appearance of
the three images constituting the polychrome picture in the apparatus which
has furnished the same. The exactness in the separation and the adjustment
of the reflectors and also the exactness in the separation and the arrangement
on one and the same straight line of the three lenses need not be troubled about;
and the same remark applies to the symmetrical arrangement of the three
obtained images, as has been stated, that is to say an arrangement in which the
distance from one another upon one and the same straight line, is equal. Only
three conditions have to be observed: 1. The relative positions and the adjust-
ment of the three reflectors must, during the examination of the triple-image
be absolutely the same as during the exposure: 2. The relative positions of
the three lenses must be absolutely the same, during the examination of the
triple-image, as during the exposure: 3. The perfectly straight or more or less
broken line which passes through one and the same point of the three representa-
tions or prints upon the plate carrying the same, must, during the examination
of the coloured representation, have the same lateral adjustment, relatively to
the perfectly straight or more or less broken line which passes through the axes
or the centres of the three lenses, or during the exposure.
In order to fulfil the two first conditions it is sufficient to give a complete
fixity to each of the two systems of parts constituting the apparatus namely:
the three reflectors, on the one hand, the three lenses on the other hand. In order
to fulfil the third condition it is necessary to maintain during the whole series
of operations, a perfect locking of the negative plate and of the positive plate,

page_text: .
of each one individually as well as of both together, at the moment when one
of them receives an impression below the other; and this locking or registering
should be effected constantly only upon one and the same side, namely one
of the two long sides which simultaneously limit the three images.
The locking or registration of the negative plate at the moment of exposure
is effected by the aid of a screw, which by acting upon its edge causes it to bear
only with the two ends of its opposite edge upon two projections or shoulders
provided on the recessed part of the holder in which it is introduced. In this
manner it can assume only one position even if its section should be irregular.
It matters not that the two small outer ends of the recessed parts leave free
play to the plate which need only be locked or wedged in the other direction.
In order to prevent actual contact of the end of the screw with the edge of
the plate, a steel plate is arranged in the recess, this plate being rivetted thereto
at its ends and covered with a strip of felt, leather, fabric or thin bristol board.
If the apparatus, constructed with a view to permit of a less primitive or
restricted use, is fitted with frames, in numbers in proportion to the number
of objects desired to be taken in a single excursion, each of these frames must
be adapted to be wedged or registered exactly in the apparatus. For this pur-
pose a guide in which all the frames are to be introduced is appreciably larger
than the frames themselves. The latter being introduced in to this guide, meet
laterally a spring, rivetted only at one of its ends. This spring acting only
by its elasticity forces each frame to adjust itself flush with the opposite edge
of the guide.
The locking of the positive plate during the period of its impression below the
negative plate, is effected by means of a block. The two plates bear, with
their own weight, at their lower edges against two shoulders. It is indispen-
sable, during this operation to choose for the lower edge of the negative plate
the one which has been locked or wedged up, originally against the shoulders of
the frame of the chromographic chamber.
The positive plate is thus printed with accuracy without recourse being had
to a pressure frame, provided that the light only emanates from a fixed luminous
point, not too near the plates, such for instance as a magnesium flame or a
gas burner or the like.
It is evident from the preceding that the triple-device obtained under these
conditions, being subsequently placed in the apparatus and locked or wedged
up by the same edge as in the operation just described, will present itself
under conditions of registration identical to those of the triple-phototype which
had furnished the same. The gelatine layer will be forcibly turned up as though
it was applied, during the exposure of the negative, against the gelatine layer
of the latter, which layer was turned down. The said layer will only be raised
to an extent equal to the thickness of the plate; the simple or compound eve
piece which serves for observing the triple image, amply remedying the slight
loss of distinctness due to this small increase in the distance of the lenses.
In order to correct the defects of the points of junction or registration which
may accidentally occur during observation, the shoulders of the frame are pro-
vided with screws having milled heads, and the operation of which permits of
very conveniently restoring the coincidence of the lines of the three chromo-
graphic images.
On using an apparatus such as described in combination or not, with its inter-
changeable frames, a result is obtained which in itself is very important; namely
that of permanently registering the view--for this single apparatus-of all
synthetical images which it has furnished. It is however optional, as will pre-
sently be seen, to render all the apparatus interchangeable, or what amounts to
the same thing, to render all the triple images or chromograms interchangeable
from one apparatus to the other; thus, by making use of any apparatus, one
will obtain the corresponding view of a chromoscopic object obtained with
another similar one. The combination of the apparatus, with a very simple

page_text: device will permit, by the aid of a previous and likewise very simple operation,
to thus transform these apparatus, which are of one and the same shape, into
interchangeable instruments.
Two of the three interior lenses, for instance the two outer ones, instead of
being fixed, are susceptible of a very slight displacement in all directions, but
only in their plane which is likewise that of the frame serving for mounting
each one of them. This frame itself is rendered slightly movable in the same
plane. For this purpose each of the two frames has provided at its two ends
small projections serving as handles which pass through the walls of the cham-
ber through suitable openings; these handles thus project outside the chamber,
one to the right and the other to the left, relatively to the observer who looks
through the eye-piece.
On the other hand one will have temporarily locked or wedged up in the
apparatus and in the place of a chromogram--a glass plate or opal glass, on
which is drawn a regular triple geometrical figure, which is a very fine photo-
graphic reduction. This figure serves as a standard type for all similar
apparatus as regards shape. Reduced to more simple expression, it consists of
three points provided upon one and the same straight line dividing the plate in
its centre and parallel to the fixed edge of the plate. These three points, deter-
mined each by the crossing of two very fine lines, are spaced to an extent equal
to that chosen for the spacing of the centres of the lenses.
If under these conditions, the eye is applied against the opening of the eye-
piece, a bundle will be observed composed of six lines intersecting each other in
pairs. They are coloured if the coloured screens have been retained in their
recesses or rebates, and uncoloured if the latter have been removed. It would
be a very accidental occurrence, whatever care may have been taken in the con-
struction of this apparatus, if the three crossing intersections registered with
accuracy. By causing one or both of the two movable lenses one after the other
to slide, by the aid of their handles the three intercrossings or markings can be
combined optically, the third lens which corresponds to the fixed median lens
remaining stationary. Whenever one position has been found the position is
fixed definitively by the aid of screws entering the parts projecting from the
chamber. The ends of the extensions being hinge-jointed may be subsequently
folded down.
The optical registration may also be effected by operating not the lenses but
the reflectors. The inclination of the latter may be slightly modified by past-
ing upon the two frames or parts, inclined to an angle of 450, supporting them,
thin pieces of paper of varying thicknesses. The adjustment of the mirrors
would be rendered very simple by causing them to rest upon three points, two
of which would be situated at the ends of one and the same edge, and the third
in the middle of the opposite edge. But the adjustment would require more
time than in the case where the first method is employed.
The apparatus such as described gives, in spite of the primitive and elemen-
tary nature of its constituent parts, very satisfactory results. It will never-
theless not be superfluous, if greater expense be not objected to, to apply cer-
tain advantages and refinements thereto which are obtained by the use of achro-
matic lenses, or even by the combination of two lenses properly adjusted (double
objectives). One will thus obtain apparatus, acting slightly more rapidly, per-
mitting especially of operating with a larger opening of the diaphragm and of
obtaining images which will not only be correct and registered when virtually
examined in the apparatus, but will be susceptible of being pigmentarily taken
by contact.
The system of the reflector may receive the following modifications:
Two unsilvered glass plates (arranged at an angle of 90° to each other and 45°
to the sensitised plate, in opposite directions) transmit one image say the central,
and two silvered glass plates receive each a reflected image from one of the
plain plates and reflect it to the other portion of the sensitised plate. The cen

page_text: tral image formed directly (without reflection) through the two transparent
reflectors is in this case the most luminous; and it is in front of this one that
the red-orange screen has to be arranged. The two other images are each formed
after two successive reflections, the first of which, effected by a transparent
reflector, greatly reduces the amount of luminous rays as in the preceding
apparatus these images being then transmitted to the sensitised plate by the
silvered reflectors. The triple image is to be observed by turning the bottom
of the apparatus slightly up towards the sky or light, unless a large outer re-
flector be employed.
In another modification two unsilvered glass plates and a silvered glass re-
flector are used as in the first case, but the unsilvered reflectors are arranged
in the opposite direction, i.e., inclining from left to right.
The image produced by the orange light must be formed by the inclined
silvered reflector, two supplementary silvered glass plates, arranged normally
to the reflected rays reflecting the other images from the unsilvered reflectors.
The paths traversed by the three bundles are here strictly equal, which results
in certain advantages from an optical point of view; but the construction is
more complicated, and the third proof or impression, namely that of the red-
orange light, when examined upon the plate outside the apparatus, is inverted,
thereon, the objects appear turned upside down; this being however a slight
disadvantage, seeing that the law of reversion causes them to be seen in the
true direction as in the two other proofs or impressions when once the plate has
been placed in the apparatus. Moreover the plates must be locked or wedged
up at two corresponding sides forming an angle, and no longer at a single side,
otherwise the red-orange would not appear at the same height as the other two.
In another modification the third image, namely that of the red-orange light,
is no longer reversed upon the plate relatively to the two others, as was the case
in the last construction; for its image is now, like the two others, the result of
two reflections, the first one, from an unsilvered glass plate, and the second from
a silvered class plate, the third reflector in this case being also transparent and
inclined in the same manner as the others, and provided with a silvered reflector
like them. On the other hand, it is much less luminous, a defect which will be
partly remedied by superposing-without cementing them-not two unsilvered
glass plates, as has been stated before, with regard to the green image, but
several unsilvered glass plates.
It goes without saying that the different constructions indicated in this speci-
fication are capable of being doubled with a view to produce stereoscopic effects.
It is likewise evident that the synthetical immaterial images, such as seen
in the apparatus may be thrown through the apparatus itself upon a screen.
It is, of course, necessary that in order to obtain this result, an intense light
should be concentrated upon the constituent images. For this purpose one
single focus may be employed, either by dividing the bundle of luminous rays
into three by the aid of a combination of reflecting mirrors analogous to those
above described, or by having recourse to a lantern of a special shape, the light
of which will be lengthened, in the direction of the plate, to the three images,
and of which the condenser and the reflector, instead of being spherical, will
be cylindrical.
With regard to the supporting frame, it may be useful to mention that the
most varied artistic effects can be obtained, if so desired, by an assortment of
frames of this kind, the three openings of which will be furnished with unequally
transparent screens. It will be moreover interesting, either for studying the
subject, or by way of recreation, to effect transpositions of colours by the aid
of a set of frames furnished with screens of the various colours, these frames
being applied after removing the coloured interior screens.
1000
BOULT & WADE,
Agents for the Applicant,

page_text: Improvements in or relating to the Production and Exhibition of
Photographic Representations in Natural Colours.
A communication from Louis Ducos Du HAURON, Chemical Engineer, of Saint-
Maurice, Paris, in the Republic of France.
1, ALFRED JULIUS BOULT, of 111, Hatton Garden, in the County of London,
Chartered Patent Agent, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
This invention relates to an apparatus by the aid of which the operation of
the light taking place and manifesting itself in the dark upon the photographic
plate, when the ordinary operative method is employed, will automatically pro-
duce a view of the object in its original colours in the said apparatus, without
a fresh operation being necessitated.
Two principles serve as a basis for the construction of the device which will
now be described:
1. That of reversing the direction in which the luminous rays travel.
2. That by virtue of which an object reflected by the two opposite faces of a
non-plated (or unsilvered) glass plate, ceases to present double outlines, if between
the glass plate and the object a convergent lens is interposed, in the principal
focus of which the object is placed, and this irrespective of what may be the
focal length; the effect of the lens being to place the object optically at infinity;
inversely, the same lens has the property of forming in its principal focus a
non-doubled image of a distant object reflected by the non-plated (or unsilvered)
glass plate.
In the acompanying drawing ;-
Figure 1 represents the apparatus in the position it occupies at the moment
of exposure.
Figure 2 is a cross section showing a method of securing the sensitized plate.
Figure 3 represents the same apparatus in the position preferably imparted
to it when, on looking into the apparatus, one observes the polychromatic result..
Figures 4, 5 and 6 represent detail parts completing the different functions"
of the apparatus represented in Figures 1, 2 and 3.
Figures 7, 8 and 9 are views serving to complete the explanations given in
the following description, concerning the different means for marking or regi-
stering the object being to render all apparatus interchangeable.
Figures 10, 11 and 12 are diagrammatic views shewing modifications of the.
device represented in Figures 1, 2 and 3.
Figures 13 and 14 shows respectively a side elevation and vertical cross sec-
tions of the apparatus representing a variation in the manner of optical regi-
stration according to which the apparatus may be constructed.
The apparatus consists of a box or casing composed of two parts 13 and 14;
the former 13 is divided by two partitions 15 and 16, forming three spaces, into
which the luminous rays enter respectively through three convergent lenses 24,
25, and 26, of one and the same focal length, and arranged rigidly upon the
vertical wall 17, separating the two parts 13 and 14 of the apparatus; these
lenses may be simply ordinary non-achromatic lenses, and they may be of cir-
cular or rectangular form, as desired.
The second part 14 comprises an opening 20 for the admission of luminous

page_text: rays for taking the photograph or negative or for the admission of the visual
rays, when one observes the positive triple-photograph.
Below this opening 20 are arranged, at an angle of 45° three glass plates 21,
22 and 23, two of which, namely 21 and 22 are non-plated (or unsilvered) whilst
the third 23 is silvered.
At the end of the part 13 of the apparatus, and facing the partition 17 a
.frame 18 is placed, in which are arranged a blue-violet screen 27 corresponding
to the unsilvered glass plate 21, a green screen 28, corresponding to the other un-
silvered glass plate 22, and a red-orange screen 29 corresponding to the silvered
glass plate 23. Behind this frame 18 a sensitized pan-achromatic or orthochro-
matic plate is placed, which is arranged in a frame or holder 19 at the prin-
cipal focus of the lenses, and on which plate are received the impressions of
the images 31, 32 and 33 respectively passing through the screens 27, 28
and 29.
Above the opening 20 a removable support 45 is placed on which is mounted
at an angle of 45°, a mirror 34 serving to reflect the images to be photographed;
this mirror 34 which is only provided on the apparatus for the purpose of tak-
ing the photograph, can be replaced by a prism. with total reflection. Upon the
front of the apparatus a convergent lens 35 of comparatively great focal length
is placed which serves as a magnifier" or focussing lens, the same is thus used
only at the moment of taking the photograph, and only in case where the object
'to be reproduced, lies very near, its object being then to transport it optically
to infinity. A lens 36 (Figure 3) very slightly concave and serving as the eye
piece is applied when the triple-image is to be observed and has for its object to
render the view of the latter very clear. It is preferably covered with "a dia-
phragm 37, the small opening of which occupies exactly the optical centre of
the apparatus. The dotted lines indicate in the two figures the direction in
which the luminous rays travel.
The rays reflected by the mirror 34 (Figure 1) traverse the diaphragm 38 in
the opening 20, then are divided into three bundles; the first is reflected by
the unsilvered glass plate 21, traverses its lens 24, then the blue-violet screen 27
and forms the image 31; the second is reflected by the unsilvered glass plate 22,
traverses its lens 25, then the green screen 28 and forms the image 32; the third
which is the strongest, is reflected by the silvered glass plate 23, traverses its
lens 26, then the red-orange screen 29 and forms the image 33. The red-orange
light, being the least actinically active of the three lights transmitted by the
different screens, necessitates the use of a silvered glass plate which, reflecting
almost the whole of the rays it receives reduces the exposure required for the
third image to that of the second. In order to control the action of the blue-
violet light, which would require an exposure of much less duration for the first
image than for the two others, upon the opening 20 (only for the time of expo-
sure is placed, a green transparent screen 39 (Figure 5) which freely transmits
only the green and red rays, but the centre of which is pierced with a narrow
opening 40 transmitting, as far as the blue violet light is concerned, only suffi-
cient light to form the corresponding image, during the same time of exposure
as the two other parts of the apparatus. Under these conditions the equili-
brium between the three images would not be perfect, in the case of panchro-
matic plates being used the image formed by the green light would appear
with a slight delay; a very simple remedy for which consists in covering the un-
silvered glass plate 22 with a second unsilvered glass plate (which is represented
in Figures 1 and 3) in perfect contact therewith. The two glass plates are con-
nected together say by means of strips of paper, pasted over their edges. Great
care must be taken not to cement the two glass plates together over their active
surfaces; otherwise the two supplementary reflections which are required
would be destroyed.
When the triple negative or chromogram is obtained a positive is made by
contact upon opal glass or upon polished glass, using preferably à special plate

page_text: for positives, and this triple positive is placed in a frame 53, arranged on the
apparatus in the same position that the frame 19 carrying the negative plate
occupied during the exposure, care being taken that each of the three positives
occupies the position which the negative, furnishing the same, formerly occu-
pied, and that the colour screens are on their part maintained in their respec-
tive places; only the gelatine layer or film must be placed, upwards, and not
below as during exposure of the negative. Upon the bottom of the apparatus
(Figure 3) a frame is applied formed of a plate 41 (Figure 4) in which three
openings 42, 43, 44, corresponding to the three positive images, are provided,
in one of them namely 44, a transparent membrane screen or film of a somewhat
dark grey is placed, the object of which is to moderate the brilliancy of the
third image, illuminated by the red-orange screen and reflected by the silvered
glass plate 23. The frame or support 45 carrying the eye piece 36 of slight
divergency is then put in place. This last frame 45 should be black or of a
dark colour and should extend sufficiently in width in order that the eye which
does not look into the apparatus may remain open without affecting the clear
vision of the other eye.
The instrument being appropriately inclined toward the light, as shewn in
Figure 3, if the eye is applied against the opening of the diaphragm 37 one
observes in the direction of the mirrors an amplified polychromatic image being
the synthetical result from the combination or fusion of the three black posi-
tives, one illuminated by red-orange light, the second by green and the
other by blue-violet. This image appears identical--not only as regards colour,
but as regards perspective and the erection of lines-to the photographed object,
as if latter were present to the eye placed in the centre of the diaphragm. The
image is entirely free from aberration, from refrangibility and from distortion,
notwithstanding the use of non-achromatic lenses, and the arrangement of the
latter at large and unequal distances from the diaphragm. This general cor-
rection is due to the fact that the rays, in returning from the three images to
the eye, through the combination of lenses and reflectors, follow exactly the
same path which they had traversed originally.
If it is desired to increase the field or angle of view which is naturally and
strictly limited according to the construction of the apparatus all that is neces-
sary is to arrange over the opening 20 (Figures 1 and 2) a small tube 46 (Figure 6)
provide at each end with a lens the one in front 47, being divergent and the
one at the back 48 convergent, the focus of the former being shorter than that.
of the second. The whole combination thereof constitutes an inverted Galilea
lens, and possesses two properties: 1) that of collecting and concentrating, in
the field occupied by each of the three images upon the plate, a larger portion of
the horizon; 2) that, inversely to the former, of exhibiting during the obser
vation of the triple image in the apparatus, this same portion under the real
angle of magnification. This small supplementary, objective permits of dis-
pensing with the focussing lens as well as the lens of slight divergence which
serves as the eye-piece all that is necessary is to adjust the two constituent
lenses to a slight extent relatively to each other until the correct focus is ob-
tained. On this objective the different diaphragms as well as the yellow per-
forated circular screen are adjusted.
According to the law of reversion of the direction of luminous rays, the sym-
metrical and mathematically correct arrangement of the three internal mirrors
and of the three lenses is by no means necessary for the separate appearance of
the three images constituting the polychrome picture in the apparatus which
has furnished the same. The exactness in the separation and the adjustment
of the reflectors, and also the exactness in the separation and the arrangement
on one and the same straight line, of the three lenses need not be troubled about,
and the same remark applies to the symmetrical arrangement of the three
obtained images, as has been stated, that is to say an arrangement in which the
distance from one another upon one and the same. straight line, is equal. Only

page_text: three conditions have to be observed: 1. The relative positions and the adjust-
ment of the three reflectors must, during the examination of the triple-image
be absolutely the same as during the exposure; 2. The relative positions of
the three lenses must be absolutely the same, during the examination of the
triple-image, as during the exposure; 3. The perfectly straight or more or less
broken line which passes through one and the same point of the three representa-
tions or prints upon the plate carrying the same, must, during the examination
of the coloured representation, have the same lateral adjustment, relatively to
the perfectly straight or more or less broken line which passes through the axes
or the centres of the three lenses, as during the exposure.
In order to fulfil the two first conditions it is sufficient to give a complete
fixity to each of the two systems of parts constituting the apparatus namely:
the three reflectors, on the one hand, the three lenses on the other hand. In order
to fulfil the third condition it is necessary to maintain during the whole series
of operations, a perfect locking of the negative plate and of the positive plate,
of each one individually as well as of both together, at the moment when one
of them receives an impression below the other; and this locking or registering
should be effected constantly only upon one and the same side, namely one
of the two long sides which simultaneously limit the three images.
The locking or registration of the negative plate at the moment of exposure
is effected by the aid of a screw 49 (Figure 2) which by acting upon its edge
causes it to bear only with the two ends of its opposite edge upon two projec-
tions or shoulders 50 and 51 provided on the recessed part of the holder in which
it is introduced. In this manner it can assume only one position even if its
section should be irregular.
It matters not that the two small outer ends of the recessed parts leave free
play to the plate which need only be locked or wedged in the other direction.
In order to prevent actual contact of the end of the screw 49 with the edge
of the plate, a steel plate 52 is arranged in the recess, this plate being rivetted
thereto at its ends and covered with a strip of felt, leather, fabric or thin Bristol
board.
If the apparatus constructed with a view to permit of a less primitive or
restricted use, is fitted with frames in numbers, in proportion to the number of
objects desired to be taken in a single excursion, each of these frames must be
adapted to be wedged or registered exactly in the apparatus. For this purpose
a guide 54 in which all the frames are to be introduced is appreciably larger
than the frames themselves. The latter being introduced into this guide, meet
laterally a spring 55 rivetted only at one of its ends. This spring acting only
by its elasticity, forces each frame to adjust itself flush with the opposite edge
of the guide.
The locking of the positive plate during the period of its impression below the
negative plate, is effected by means of a block 56 represented in Figure 7. The
two plates bear, with their own weight, at their lower edges against two shoulders,
one of which is represented at 57. It is indispensable, during this operation to
choose for the lower edge of the negative plate the one which has been locked
or wedged up, originally against the shoulders of the frame of the chromographic
chamber.
The positive plate is thus printed with accuracy without recourse being had
to a pressure-frame, provided that the light only emanates from a fixed luminous
point, not too near the plate, such for instance as a magnesium flame or a
gas burner or the like.
It is evident from the preceding that the triple-device obtained under these
conditions, being subsequently placed in the apparatus and locked or wedged
up by the same edge as in the operation just described, will present itself
under conditions of registration, identical to those of the triple-phototype which
had furnished the same. The gelatine layer will be forcibly turned up as though
it was applied, during the exposure of the negative, against the gelatine layer

page_text: of the latter, which layer was turned down. The said layer will only be raised
to an extent equal to the thickness of the plate; the simple or compound eye-
piece which serves for observing the triple image, amply remedying the slight
loss of distinctness due to this small increase in the distance of the lenses.
In order to correct the defects of the points of junction or registration which
may accidentally occur during observation, the shoulders 50, 51 of the frame 53
are provided with screws 58, 59 having milled heads, and the operation of which
permits of very conveniently restoring the coincidence of the lines of the three
chromographic images.
On using an apparatus such as that described in combination or not, with its
interchangeable frames, a result is obtained which in itself is very important:
namely that of permanently registering the view for this single apparatus of all
synthetical images which it has furnished. It is however optional, as will pre-
sently be seen, to render all the apparatus interchangeable, or what amounts in
the same thing, to render all the triple images or chromograms interchangeable
from one apparatus to the other; thus, by making use of any apparatus, one
will bbtain the corresponding view of a chromoscopic object obtained with
another similar one. The combination of the apparatus, with a very simple
device will permit, by the aid of a previous and likewise very simple operation,
to thus transform these apparatus, which are of one and the same shape, into
interchangeable instruments.
Two of the three interior lenses for instance the two outer ones 24 and 26
instead of being fixed are susceptible of a very slight displacement in all direc-
tions, but only in their plane which is likewise that of the frame 60 serving for
mounting each one of them. This frame itself is rendered slightly movable in
the same plane. For this purpose each of the two frames 60 has provided at
its ends small projections 61 serving as handles (Figure 8) which pass through
the walls of the chamber through suitable openings, these handles thus project
outside the chamber, one to the right and the other to the left, relatively to the
observer who looks through the eye piece.
On the other hand one will have temporarily locked or wedged up in the
apparatus and in the place of a chromogram-a glass plate or opal glass, on
which is drawn a regular triple geometrical figure, which is a very fine photo-
graphic reduction (Figure 9). This figure serves as a standard type for all similar
apparatus as regards shape. Reduced to more simple expression, it consists of
three points provided upon one and the same straight line dividing the plate in
its centre and parallel to the fixed edge of the plate. These three points, deter-
mined each by the crossing of two very fine lines, are spaced to an extent equal
to that chosen for the spacing of the centres of the lenses.
If under these conditions, the eye is applied against the opening of the eye
piece, a bundle will be observed composed of six lines intersecting each other in
pairs. They are coloured if the coloured screens have been retained in their
recesses or rebates, and uncoloured if the latter have been removed. It would
be a very accidental occurrence, whatever care may have been taken in the con-
struction of this apparatus, if the three crossing intersections registered with
accuracy. By causing one or both of the two movable lenses one after the other
to slide, by the aid of their handles the three intercrossings or markings can be
combined optically, the third lens which corresponds to the fixed median lens
remaining stationary. Whenever one position has been found, the position is
fixed definitively by the aid of screws entering the parts projecting from the
chamber. The ends of the extensions, being hinge-jointed may be subsequently
folded down.
The optical registration may also be effected by operating not the lenses but
the reflectors. The inclination of the latter may be slightly modified by past-
ing upon the two frames or parts inclined to an angle of 45° supporting them,
thin pieces of paper of varying thicknesses. The adjustment of the mirrors
would be rendered very simple by causing them to rest upon three points, two

page_text: of which would be situated at the ends of one and the same edge, and the third
in the middle of the opposite edge. But the adjustment would require more
time than in the case where the first method is employed.
The apparatus such as described gives, in spite of the primitive and elemen-
tary nature of its constituent parts, satisfactory results. It will never-
theless not be superfluous if greater expense be not objected to, to apply cer-
tain advantages and refinements thereto which are obtained by the use of achro-
matic lenses or even by the combination of two lenses properly adjusted (double
objectives). One will this obtain apparatus, acting slightly more rapidly per-
mitting especially of operating with a larger opening of the diaphragm and of
obtaining images which will not only be correct and registered when virtually
examined in the apparatus, but will be susceptible of being pigmentarily taken
by contact.
The system of reflectors may receive the following modifications;-
―:
In Figure 10, 62 and 63 are two unsilvered glass plates. 64 and 65 are two
silvered glass plates. The central image 32, formed directly (without reflection)
through the two transparent reflectors 62 and 63, is in this case the most lumi-
nous; and it is in front of this one that the red-orange screen has to be arranged.
The two other images are each formed, as shown, after two successive reflections,
the first of which effected by a transparent reflector, greatly reduces the amount
of luminous rays as in the preceding apparatus; these images being then
transmitted to the sensitised plate by the silvered reflectors. The triple image
is to be observed by turning the bottom of the apparatus slightly up towards
the sky or light, unless a large outer reflector 66 be employed.
In Figure 11 67 and 68 are two unsilvered glass plates 69 being the silvered
glass reflector by which the image produced by the orange light must be formed
at 33; 70 and 71 are two supplementary silvered glass plates, arranged normally
to the reflected rays 67 and 70, and 68--71 which they normally reflect in order
to form the images 31 and 32. The paths traversed by the three bundles are
here strictly equal, which results in certain advantages from an optical point of
view; but the construction is more complicated, and the third proof or impres-
sion, namely that of the red-orange light, when examined upon the plate out-
side the apparatus, is inverted thereon, the objects appear turned upside down,
this being however a slight disadvantage, seeing that the law of reversion
causes them to be seen in the true direction as in the two other proofs or impres-
sions when once the plate has been placed in the apparatus. Moreover the plates
must be locked or wedged up at two corresponding sides forming an angle, and
no longer at a single side, otherwise the red-orange would not appear at the
same height as the other two.
In Figure 12 the third image 33, namely that of the red-orange light, is
no longer reversed upon the plate relatively to the two others, as was the case
in Figure 11 for its image is now, like the two others 31, and 32, the result
of two reflections, the first one, from an unsilvered glass plate 72, and the second
from a silvered glass plate 73. On the other hand, it is much less luminous,
a defect which will be partly remedied by superposing-without cementing
them not two unsilvered glass plates, as has been stated before, with regard
to the green image, but several unsilvered glass plates.
It now only remains to describe Figures 13 and 14 representing a modification of
the methods of optical registration of the three images constituting the poly-
chromatic picture.
To effect this optical registration of the three images constituting the poly-
chromatic picture as well as the inter-registration, or interchangeability from
one apparatus to another, two means have been referred to: the first consisting
in displacing the plane of the lenses, the second in varying the inclination of
the reflectors.
Such operations, however, are of a very delicate nature inasmuch as the

page_text: slightest change in the position of a lens or the inclination of the reflectors will
be followed by a very marked displacement of the corresponding image.
The modification in the method of registration as illustrated in Figures 13
and 14 fully secures the object in view, owing to the amplitude of movement
required by the supplementary parts with which it is provided.
As will be readily understood the devices consist of three unsilvered glass
plates 80, 81, and 82 placed in the spaces between the lenses 24, 25, 26 and their
respective images 31, 32, 33 parallel to the plane both of the lenses and the
images.
Thus the images are transmitted through these three supplementary glasses 80,
81, 82 and with the interposition of the latter they are also viewed.
Two of these glasses, preferably the central one and one of the outer glasses,
in this case 81 and 82, can be made to swing, each separately, round its hori-
zontal or vertical axis, in the present case the horizontal axis. The movement
can be effected for each of them by means of a small lever 83 in the shape of
a pointer, placed outside the apparatus on one of its large sides and mounted on
an axle or pin serving as one of the pivots of the glass, the pivots being formed
on two channel plates or clamps fastened to the opposite edges of the glass.
The third glass is made to swing in the opposite direction, i.e., around its
vertical axis which is perpendicular to the small sides of the apparatus, the ad-
justment being also carried out in this case, by means of a similar lever 83,
placed on the corresponding small side of the apparatus.
If, under these conditions one of the two first named glasses 81, 82 is inclined
in one or the other direction by means of the lever 83, the light rays, by passing
obliquely through the said glasses will be slightly deviated owing to refraction,
and the corresponding images will therefore be displaced to a relatively small
extent, either upwards or downwards..
If now the third glass 80 is suitably inclined by actuating its levers 83,
either in one or the other direction, the image will, owing to the same cause,
be slightly displaced, this time however from the right to the left, or as the case
may be, from the left to the right.
The lenses and glasses having been adjusted at first approximately only by
the maker, it will be easy for him by observing through the eye-piece of the
apparatus a triple geometrical figure introduced in the apparatus as represent-
ing an image (and which serves as standard registration device for the relative
adjustment of all the apparatus) to correct, by the adjustment of the
levers 83, two kinds of registration errors: firstly, one concerning the lenses and
resulting from the fact that the optical centres of the latter are not suitably
adjusted, or are not arranged in the same straight line, and secondly, that of
the reflectors resulting from insufficient precision with regard to their angle of
inclination.
When once the plates are adjusted in their correct positions the operator will
screw up a nut or button 85 on the axle itself, and identifies this position by a
mark indicating it as the one which it should always occupy when taking a
chromographic negative.
This arrangement of levers and nuts also enables an amateur to easily register
the positive chromographs which may not happen. to register in his apparatus
owing to wrong adjustment of the lenses or other fault previously committed.
It goes without saying that the different constructions indicated in this speci-
fication are capable of being doubled with a view to produce stereoscopic effects.
It is likewise evident that the synthetical immaterial images, such as scen
in the apparatus may be thrown through the apparatus itself upon a screen.
It is, of course, necessary that in order to obtain this result, an intense light
should be concentrated upon the constituent images. For this purpose one
single focus may be employed either by dividing the bundle of luminous rays
into three by the aid of a combination of reflecting mirrors analogous to those

page_text: above described, or by having recourse to a lantern of a special shape, the light
of which will be lengthened, in the direction of the plate to the three images,
and of which the condenser and the reflector, instead of being spherical, will
be cylindrical.
With regard to the supporting frame (represented in Figure 4) it may be use-
ful to mention that the most varied artistic effects can be obtained, if so desired,
by an assortment of frames of this kind, the three openings of which will be
furnished with unequally transparent screens. It will be moreover interesting
either for studying the subject, or by way of recreation, to effect transpositions
of colours by the aid of a set of frames furnished with screens of the various
colours, these frames being applied after removing the coloured interior screens.
Having now particularly described and ascertained the nature of this said
invention, as communicated to me by my foreign correspondent, and in what
manner the same is to be performed, I declare that what I claim is:
1. Apparatus for the production and exhibition of photographs of objects in
their natural colours comprising a casing divided into three compartments and
provided with a single diaphragm as 20 in combination with three lenses, one
for each compartment, for transmitting the image to a sensitised surface at the
focus of said lenses on the one hand, and for effecting the optical fusion of three
views obtained in the way into a single absolutely correct image which views
.considered separately and comparatively, contain irregularities and distortions
showing that if these three views had been obtained by a special diaphragm for
each objective they would have given rise, when observed synthetically in the
apparatus, to an image not only irregular and distorted, but the three compo-
site parts of which would have shown differences of perspective becoming more
and more pronounced from the centre outwards and that in spite of the use of
very exact objectives substantially as described.
2. A form of construction of apparatus of the kind described comprising three
converging lenses of the same focus for producing on a sensitised surface three
images of an object the rays of which object after having passed through a
single diaphragm being reflected by transparent and reflecting mirrors in as
many images as there are converging lenses; these lenses and mirrors being
combined with suitable coloured screens whereby the light produces on a single
plate, the position of which can be regulated, its chromographic effect so that
after obtaining a positive representation from the negative plate thus produced,
and placing said positive in the same apparatus a representation of the object
in its natural colours can be viewed substantially as described.
3. In apparatus of the kind described, means for registering the three images
constituting the polychromatic view comprising three unsilvered glasses 80, 81,
82, arranged respectively in the space between each lens and its corresponding
photographic plate, the rays of the pictures passing through the said glasses,
two of the glasses, the central one and one of the end glasses being mounted so
as to swing round a horizontal axis while the remaining glass is arranged to
swing round a vertical axis perpendicular to the first axis, in such a manner that
by adjusting said glasses the luminous rays forming the image can be deflected
either downwards or upwards by means of the two first-named glasses, or from
right to left, and inversely, by means of the third glass for the purpose of ob-
taining an absolutely correct registration, of the three images substantially as
described.
4. Apparatus for the production and exhibition of photographic views in
natural colours comprising a chamber divided into three compartments, a plate
holder and colour screens at one end a series of silvered and unsilvered reflectors
at the other end of the partitioned chamber, three intermediate lenses as a
diaphragm, such as 20, substantially as described.
5. Apparatus for the production and exhibition of photographic views in
natural colours comprising a chamber divided into three compartments, a plate

page_text: holder and colour screens at one end a series of silvered and unsilvered reflectors
at the other end of the partitioned chamber, three intermediate lenses as a dia-
phragm, such as 20 a removable reflector 34, substantially as described.
6. Apparatus for the production and exhibition of photographic views in
natural colours comprising a chamber divided into three compartments, a plate
holder and colour screens at one end a series of silvered and unsilvered reflectors
at the other end of the partitioned chamber, three intermediate levers as a dia-
phragm, such as 20, a removable reflector 34 and a lens 35, substantially as
described.
7. In apparatus of the kind described a series of silvered and unsilvered in-
clined glasses for transmitting and reflecting a view transmitted though a
single diaphragm, superposed but not cemented glasses being employed in such
cases where a strong light action is required, substantially as described.
8. In apparatus of the kind described a series of silvered and unsilvered in-
clined glasses for transmitting and reflecting a view transmitted through a
single diaphragm, superposed but not cemented glasses being employed in such
cases, when a strong light action is required, in combination with one or more
refracting glasses arranged parallel to the vertical plane of the photographic
plate, substantially as described.
9. In apparatus of the kind described means for registering the position of
the photographic plate comprising a frame 19, with adjusting screws 49, 58
and 59 substantially as described.
10. In apparatus of the kind described means for adjusting the lenses in the
apparatus comprising a carrier with slotted sides, lens holders 60 with projecting
arms 61 and means for securing same in position, substantially as described.
11. In apparatus of the kind described a diaphragm consisting of a coloured
dise provided with a central aperture or clear portion, substantially as described.
12. The complete apparatus for the production and exhibiting of photographic
views in their natural colours substantially as described or illustrated in Figure I
or in Figure 10 or in Figure 11 or in Figure 12 or in Figure 13 of the accom-
panying drawings.
Dated this 16th day of December 1899.
BOULT, WADE & KILBURN,
Agents for the Applicant.