IMPROVEMENTS IN THE COMBINATION OF LENSES FOR PHOTOGRAPHIC PURPOSES, AND IN THE MEANS FOR FOCUSSING THE SAME
Year: 1878

page_text: LETTERS PATENT to William Morgan-Brown, of the Firm of Brandon and
Morgan-Brown, Engineers and Patent Agents, of 38, Southampton Buildings,
London, and 1, Rue Laffitte, Paris, for the Invention of "IMPROVEMENTS IN
THE COMBINATION OF LENSES FOR PHOTOGRAPHIC PURPOSES, AND IN THE
MEANS FOR FOCUSSING THE SAME." A communication from abroad by John
Augustus Knapp, Photographer, Frederick William Kamping, Tobacconist,
and Robert Young Spring, Photographer, all of Cincinnati, United States of
America.
Sealed the 21st January 1879, and dated the 2nd September 1878.
66
PROVISIONAL SPECIFICATION left by the said William Morgan-Brown at
the Office of the Commissioners of Patents on the 2nd September 1878.
WILLIAM MORGAN-BROWN, of the Firm of Brandon and Morgan-Brown, Engineers
and Patent Agents, of 38, Southampton Buildings, London, and 1, Rue Laffitte,
Paris, IMPROVEMENTS IN THE COMBINATION OF LENSES FOR PHOTOGRAPHIC
PURPOSES, AND IN THE MEANS FOR FOCUSSING THE SAME.' [A communication
from abroad by John Augustus Knapp, Photographer, Frederick William Kamping,
Tobacconist, and Robert Young Spring, Photographer, all of Cincinnati, United
States of America.]
"
These improvements in the combination of lenses for photographic purposes and
in the means for focussing the same consist in placing an additional lens in front
of an ordinary portrait lens, and is so arranged, shaped, and constructed as to
change the usual result of a curved field into a flat field; it also obviates other
faults incident to spherical lenses, such as spherical abberation and distortion.
With this improved lens a small instrument is made to do the work of the largest
instrument made.
It also consists in a new device for focussing, whereby the inner sleeve to which
the ordinary lenses are attached is made to move inwardly by means of a screw-

page_text: shaped slot in the exterior sleeve and a projecting handle connected to the inner
sleeve and operating in said slot; by this means of focussing all liability of
changing the focus when the light-excluding cap is placed over or taken off the end
of tho lens is entirely obviated, as the outer sleeve remains stationary at all times.
In the accompanying Drawings,-
Figure 1 is a longitudinal sectional elevation of an ordinary photographic lens,
with the additional lens attached at the rear end thereof.
Figure 2 is a perspective view of the same with the additional lens shewn as
attached in front, the preferred location for it. This Figure also shews a modifi-
cation of the new focussing device.
Figure 3 shews the focussing device arranged in the preferred method.
Figure 4 is a longitudinal section of the same, and represents the additional lens
as plano-concave, and made achromatic; the concave side is shewn toward the
object which it should be when used on round objects or for portraiture, as it causes
more globular distortion to counteract the distortion of the other lenses. When
used as a view lense it should be reversed.
Figure 5 is a sectional elevation of an ordinary photographic lens, with arrows
representing the object before and after passing through the lens, the curved arrow
shewing the object as it would appear at its true focal position; aud Figure 6 is
used as an example and will be referred to hereafter.
Letters of like character represent corresponding parts in each of the Figures.
The ordinary photographic lens shewn by Figure 5 consists of two bi-conyex
crown glass lenses a, a¹, and two negative flint lenses b, 61, the front plano-concave
and the back negative meniscus with a diaphragm c, located at a point in the lens
where the rays or pencils of light cross each other on the axis or optical centre.
In Figure 4 the additional lens A is represented as located a short distance in
front of lens a, and the arrows B, C, and D represent the different configurations
of an object before and after passing through a photographic lens with the additional
lens attached thereto. The object being flat, as indicated by arrow B, when acted
upon by the lens, is formed in front of lens A in a curved shape of reduced
dimensions, as shewn at C, from whence it is transmitted through the ordinary
photographic lens to the negative plate, where again it is flat, as indicated by
-nrrow D. By this.combination a small lens, for example, a "half portrait," can be
made to do the work of an 8" x 4"; and under favorable conditions as to light and
rapidity of action of chemicals of a "mammoth" sized lens, on the same principle
of a small copying tube, which when attached to a box sufficiently large can enlarge
a small locket picture to any size, the size of the copied picture depending on the
distance of the ground glass from the lens, and this combination lens acts on this
principle, the front or additional lens A reduces the object and brings it within
the scope of a small lens and a much larger field of view is obtained, and the size
of the picture is dependent only on the distance of the ground glass from the lens.
The lens A is secured to a thimble E, which is provided with corresponding female
threads at each of its ends for the more ready transposition of lens A from concave
to plano side out. A handle F is secured to the inner sliding tube H, and in
moving through curved slot I causes the 'said inner tube H to move to or from the
lens A, according as the handle F is moved upward or downward, and at the same
time the exterior tube L remains fixed. By this means a more delicate focussing
device is attained, and the difficulty often experienced, that of changing the focus
when the light excluding cap is put over the end E, is entirely obviated, and the
lenses are kept well centred and not as liable to get out of order.
In the example, Figure 6, a plano-concave lens G, G¹, is shown. This lens when
intended for use, as at A, Figures 1 and 4, should be made achromatic.
A negative meniscus or a bi-concave lens may be used instead of a plano-concave.
If G and G¹ be a plano-concave lens (see Figure 6), and d, e, the axis, let the ray
G, f, fall upon the lens at G and it will be refracted in passing through the glass
and diverge from the direct line G, i, into G, e, approaching towards the perpen-
.dicular of the concave side, the ray G' being equidistant from line d, e, will diverge

page_text: in the same manner as well as the rest of the intermediate rays in proportion to
their distance from the axis of the lens and the arrow B. curved and reduced in
dimensions is reproduced, as shewn at C, and is transmitted through the lens in the
manner indicated by arrow D.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Morgan-Brown in the Great Seal Patent Office on the 20th
February 1879.
WILLIAM MORGAN-BROWN, of the Firm of Brandon and Morgan-Brown, Engineers
and Patent Agents, of 38, Southampton Buildings, London, and 1, Rue Laffitte, Paris.
"IMPROVEMENTS IN THE COMBINATION OF LENSES FOR PHOTOGRAPHIC PURPOSES,
AND IN THE MEANS FOR FOCUSSING THE SAME." A communication from abroad by
John Augustus Knapp, Photographer, Frederick William Kamping, Tobacconist,
and Robert Young Spring, Photographer, all of Cincinnati, United States of
America.
These improvements in the combination of lenses for photographic purposes and
in the means for focussing the same consist in placing an additional lens in front of
an ordinary portrait lens, and is so arranged, shaped, and constructed as to change
the usual result of a curved field into a flat field; it also obviates other faults
incident to spherical lenses, such as spherical aberration and distortion; with this
improved lens a small instrument is made to do the work of the largest instrument
made.
It also consists in a new device for focussing, whereby the inner sleeve to which
the ordinary lenses are attached is made to move inwardly by means of a screw-
shaped slot in the exterior sleeve and a projecting handle connected to the inner
sleeve, and operating in said slot; by this means of focussing all liability of changing
the focus when the light excluding cap is placed over or taken off the end of the
lens is entirely obviated, as the outer sleeve remains stationary at all times.
In the accompanying Drawings,
Figure 1 is a longitudinal sectional elevation of an ordinary photographic lens,
with the additional lens attached at the rear end thereof.
Figure 2 is a perspective view of the same with the additional lens shewn as
attached in front, the preferred location for it; this Figure also shows a modifi-
cation of the new focussing device.
Figure 3 shews the focussing device arranged in the preferred method.
Figure 4 is a longitudinal section of the same, and represents the additional lens
as plano-concave and made achromatic, the concave side is shewn toward the object
which it should be when used on round objects or for portraiture, as it causes more
globular distortion to counteract the distortion of the other lenses. When used as
a view lens it should be reversed.
'
Figure 5 is a sectional elevation of an ordinary photographic lens, with arrows
representing the object before and after passing through the lens, the curved arrow
shewing the object as it would appear at its true focal position; and Figure 6 is
used as an example and will be referred to hereafter.
Letters of like character represent corresponding parts in each of the Figures.

page_text: The ordinary photographic lens, shewn by Figure 5, consists of two bi-convex
crown glass lenses a, a, and two negative flint lenses b, b', the front plano-concave
and the back negative meniscus, with a diaphragm c'located at a point in the lens
where the rays or pencils of light cross each other on the axis or optical centre.
In Figure 4 the additional lens A is represented as located a short distance in
front of lens a, and the arrows B, C, and D represent the different configurations
of an object before and after passing through a photographic lens with the
additional lens attached thereto. The object being flat, as indicated by arrow B,
when acted upon by the lens is formed in front of lens A in a curved shape
of reduced dimensions, as shewn at C, whence it is transmitted through the
ordinary photographic lens to the negnative plate where again it is flat, as indicated
by arrow D. By this combination a small lens, for example, a "half portrait," can
be made to do the work of an "8 × 4," and under favourable conditions as to light
and rapidity of action of chemicals of a "mammoth" sized lens on the same
principle of a small copying tube, which when attached to a box sufficiently large
can enlarge a small locket picture to any size, the size of the copied picture
depending on the distance of the ground glass from the lens; and this combination
lens acts on this principle, the front or additional lens A reduces the object and
brings it within the scope of a small lens, and a much larger field of view is
obtained, and the size of the picture is dependent only on the distance of the ground
glass from the lens. The lens A is secured to a thimble E which is provided with
corresponding female threads at each of its ends for the more ready transposition
of lens A from concave to plano side out. A handle F is secured to the inner
sliding tube H, and in moving through curved slot I causes the said inner tube H
to move to or from the lens A, according as the handle F is moved upward or
downward, and at the same time the exterior tube L remains fixed. By this means
a more delicate focusing device is attained and the difficulty often experienced,
that of changing the focus when the light-excluding cap is put over the end E, is
entirely obviated, and the lenses are kept well centered and not as liable to get out
of order.
In the example, Figure 6, a plano-concave lens G, G, is shown, this lens when
intended for use, as at A, Figures 1 and 4, should be inade achromatic.
A-negative meniscus or a bi-concave lens may be used instead of a plano-concave.
If G and G¹ be a plano-concave lens (see Figure 6) and d, e, the axis, let the rays
G, f, fall upon the lens at G and it will be refracted in passing through the glass
and diverge from the direct line G, i, into G, e, approaching towards the perpen-
dicular of the concave side, the ray G¹ being equidistant from line d, e, will diverge
in the same manner as well as the rest of the intermediate rays in proportion to
their distance from the axis of the lens, and the arrow B curved and reduced in
dimensions is reproduced, as shown at C, and is transmitted through the lens in the
manner indicated by arrow D.
Having thus described the Invention, what I claim as new and desire to secure
by Letters Patent is,―
First. An additional lens A of the nature of a plano-concave lens attached to an
ordinary photographic lens, in the manner and for the purpose specified.
Second. In a photographic lens the focusing device described and shewn, as and
for the purpose specified.
In witness whereof, I, the said William Morgan-Brown, have hereunto set my
hand and seal, this Twentieth day of February, in the year of our Lord
One thousand eight hundred and seventy-nine.