IMPROVEMENTS IN PHOTOGRAPHIC LENSES
Year: 1865

page_text: LETTERS PATENT to William Bünger, of 34, Southampton Buildings,
Chancery Lane, in the County of Middlesex, Civil Engineer, for the
Invention of "IMPROVEMENTS IN PHOTOGRAPHIC LENSES."-A communica-
tion from abroad by Charles Augustus Steinheil, of Munich, in the
Kingdom of Bavaria.
Sealed the 11th May 1866, and dated the 15th November 1865.
PROVISIONAL SPECIFICATION left by the said William Bünger at the
Office of the Commissioners of Patents, with his Petition, on the 15th
November 1865.
I, WILLIAM BÜNGER, of 34, Southampton Buildings, Chancery Lane, in
the County of Middlesex, Civil Engineer, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN PHOTOGRAPHIC LENSES," to be as
follows:-
This Invention relates to the arrangement and mode of combining lenses
and parts connected therewith for photographic purposes.
The accompanying Drawing shows a vertical section of a photographic lens
constructed in accordance with these improvements, and consists of two lenses
arranged and combined with a perforated disc, diaphragm, or stop placed
midway between them, the lenses and stop being mounted or fixed in correct
position in relation to each other, as clearly shown in the Drawing.
This improved combination of parts is termed a "periscopic objective lens,"
suitable for taking correct photographic pictures, either of landscape or archi-

page_text: tecture, producing a picture strictly faithful to nature in the angles represented
and in its correct tangential projection. This arrangement of lens admits of
angles of 90°, or even more, being taken correctly, and the size of this image
is equal to double the length of the focul distance of the objective lens; the
latter is calculated from the main point or centre of the objective lens, which
lens consists of two lenses of the same description of glass and of positive
focus. These lenses may be quite equal or similar to each other, placed in
inverted position with the concave sides opposite to each other, and at such a
distance apart that all the chief rays cross each other at the same point in the
axis between the two lenses. This is the only chief point of this combination
of parts forming the objective lens, and the two lenses must be sufficiently
curved that the image shall fall within a plane which is normal to the axis,
whereby the lenses take the well-known form in which the raised surfaces
project outwards. If an opening of th of the focal distance be given to the
diaphragm or stop placed between the two lenses, then the image produced
will be sharp up to 90°, with a sufficiently good light and ninety seconds
exposure.
This improved periscopical objective lens differs from all other objective
lenses in use, not only in its construction, but also in the greatly improved
photographic effect it produces in the picture obtained by its use.
The best photographic lenses in use consist of a combination of crown and
flint glass in order to neutralize the colored rays, whereas this improved peri-
scopical objective lens consist of two lenses made of the same description of
glass.
With the American globular objective lens (which possesses greater
similarity to the periscopical objective lens than any other), the diameter
of the objective glass amounts to about th of the diameter of the image,
whereas the periscopical objective lens with equal size of image is about
four times smaller.
The image angle which the periscopical objective lens admits of taking in is
about 90°, whereas with the globular objective lens it is scarcely 50°, therefore
with equal focal distance the image surface is from four to six times larger by
the application of the periscopical objective lens, nor can any other objective
glasses be compared in their result with this improved construction of peri-
scopical objective lens, as they have a much smaller field of sight and are far
more costly to construct than this improved construction of lens. With this
periscopical lens near and distant objects appear equally clear, and it is not
necessary that the camera should be capable of adjustment, as its correct
dimensions can be determined when first made so to suit the dimensions of

page_text: the periscopical objective lens for which it is required. As the camera must
be placed when in use in a true horizontal position, according to the rules of
perspective, the image is determined without the trouble of focussing the
picture by simply observing the image angle above and on the sides of the
camera.
Thus by means of this improved construction of periscopical objective lens
it is not only possible to copy extensive landscapes, as the artist may desire to
obtain them, but the interiors of rooms or buildings may be faithfully repro-
duced, a result which has hitherto been but indifferently accomplished, at the
same time the taking of the photographic picture is rendered much more
simple, as no alteration is required in the camera.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Bünger in the Great Seal Patent Office on the
15th May 1866.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
BÜNGER, of 34, Southampton Buildings, Chancery Lane, in the County of
Middlesex, Civil Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fifteenth day of November, in the year of our Lord
One thousand eight hundred and sixty-five, in the twenty-ninth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said William Bünger, Her special licence that I, the said William Bünger,
my executors, administrators, and assigns, or such others as I, the said
William Bünger, my executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times there-
after during the terin therein expressed, should and lawfully might make,
use, exercise, and vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS
IN PHOTOGRAPHIC LENSES," a communication from Charles Augustus Steinheil,
of Munich, in the Kingdom of Bavaria, upon the condition (amongst others)
that I, the said William Bünger, my executors or administrators, by an
instrument in writing under my, or their, or one of their hands and seals,
should particularly describe and ascertain the nature of the said Invention,
and in what manner the same was to be performed, and cause the same to
be filed in the Great Seal Patent Office within six calendar months next and
immediately after the date of the said Letters Patent.

page_text: NOW KNOW YE, that I, the said William Bünger, do hereby declare
the nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement thereof, that is to say:-
This Invention relates to the arrangement and mode of combining lenses
and parts connected therewith for photographic purposes.
The accompanying Drawing shows a vertical section of a photographic lens
constructed in accordance with these improvements, and consists of two lenses
arranged and combined with a perforated disc, diaphragm, or "stop" placed
midway between them, the lenses and stop being mounted or fixed in correct
position in relation to each other, as clearly shown in the Drawing.
This improved combination of parts is termed a "periscopic objective
lens," suitable for taking correct photographic pictures, either of landscape
or architecture, producing a picture strictly faithful to nature in the angles
represented and in its correct tangential projection. This arrangement of
lens admits of angles of 90° or even more being taken correctly, the size of
the image is equal to double the focal distance of the objective lens, the latter
is calculated from the main point or centre of the objective lens, which lens
consists of two lenses of the same description of glass and of positive focus.
These lenses may be quite equal or similar to each other placed in inverted
positions with the concave sides opposite to each other, and at such a distance
apart that all the chief rays cross each other at the same point in the axis
between the two lenses. This is the only chief point of this combination of
parts forming the objective lens, and the two lenses must be sufficiently curved
that the image shall fall within a plane which is normal to the axis, whereby
the lenses take the form well known as "menicken," in which the raised
surfaces project outwards. As it is with every image plane, there are also in
this combination small dissentions from the level for rays which are lying
between the calculated points and the proportion between the length of the
first radius and that of the second radius, which being negative depends on the
dimensions of the angle of the image which is to be represented when this
dissention is most limited.

page_text: 5
if the main ray which projects lies within the prolongation of the entering ray..
If an opening of th of the focal distance be given to the diaphragm or stop
placed between the two lenses, then the image or picture produced will be.
sharp up to 90° with a sufficiently good light and ninety seconds exposure to
obtain a complete picture. Objective lenses of this improved construction
can be made of all dimensions, but it is important to observe that no other.
calculation is required for different descriptions of glass, the objective glasses
of all dimensions being obtained by multiplying the statement herein given by
the necessary formula. The dimensions of an objective glass of 90° of image:
angle are as follows:-
Diameter of both lenses quite open
Diameter of stop or diaphragm
Focus of objective glass
Size of image
1st radius
2nd radius
Thickness of lens in the centre -
Distance of lenses from each other
10"
2""
78"
156"
- 13.95" convex
- 16.50" concave
1.00
6.60
The second lens is similar to the first, but placed in an inverted position, so
0 that the concave sides are placed opposite to each other, as shown in the
Drawing hereunto annexed. This improved periscopical objective lens differs
not only in its construction and combination from all other objective lenses in
use, but also in the greatly improved photographic effects it produces in the
pictures obtained by its use.
5 The best photographic lenses in use consist of a combination of crown and
flint glass, in order to neutralize the refraction of the rays, whereas this
improved periscopical objective lens consists of two lenses made of the same
description of glass, the diameter of the periscopical objective glass amounting
only to 6 of the diameter of the image.
0
With the American globular objective lens (which possesses greater
similarity to the periscopical objective lens than any others), the diameter of
the objective glass amounts to about 4 of the diameter of the image, whereas
the periscopical objective lens with equal size of image is about four times
smaller, or in proportion to the surface 15 times smaller than that of the
5 globular objective glass.
The image angle which the periscopical objective lens admits of taking in
is about 90°, whereas with the globular objective lens it is scarcely 50°,
therefore with equal focal distance the image surface is 4-6 times larger by the
application of the periscopical objective lens, nor can any other objective'

page_text: glasses be compared in their results with this improved construction of peri-
scopical objective lens, as they have a much smaller field of sight and are far
more costly to construct than this improved construction of lens. A globular
objective glass which renders images of 26 inches diameter is about seven
times more costly than a periscopical objective glass, which renders images of
30 inches diameter, independent of its embracing a much larger field of sight
any other arrangement known.
than
In
many instances an image angle of 90° is not required, but if the image
should embrace only 75°, then the dimensions would be reduced to the burning
focus of 78", as follows:-
Diameter of the lenses (free opening)
-
""" 5
Opening of stop
-
Distance of burning focus
Dimensions of image
-
2'' 0
-
78'' 0
120 0
1st radius
2nd radius
Thickness of lens in centre
Distance between lenses
12" 502 convex
14" 418 concave
1'" 0
6'1' 26
The chemical focus with all objective glasses made of the same kind of glass
cannot be brought to coincide with the burning focus of the central rays; the
chemical focus is with the periscopical objective glasses made of mirror glass
of the burning focus shorter than the optical focus, therefore with 78"" burning
focus it is 76.5. But this does not cause the least disadvantage, because the
slide is so regulated that the body of collodion is burning focus nearer to the
objective glass than the screen or surface of the crystal or focussing glass.
With this periscopical objective lens near and distant objects appear equally
clear, and it is not necessary that the camera should be capable of adjustinent,
as its correct dimensions can be determined when first made so as to suit the
dimensions of the periscopical objective lens for which it is required, and being
once regulated it always remains correct, its crystal or focussing glass not
being required; when the "slide" is placed in position the image will be
clearly obtained. As the camera must be placed when in use in a true hori-
zontal position according to the rules of perspective, the image is determined
without the trouble of focussing the picture, by simply observing the image
angle above and on the sides of the camera.
Thus by means of this improved construction of periscopical objective lens
it is not only possible to copy extensive landscapes, as the artist may desire to
obtain them, but the interiors of rooms or buildings may be faithfully repro-
duced, a result which has bitherto been but indifferently accomplished, at the

page_text: same time the taking of the photographic picture is rendered much more
simple, as no alteration is required in the camera, the camera itself being also
much shorter.
In witness whereof, I, the said William Bünger, have hereunto set
my hand and seal, this Fifteenth day of May, in the year of our Lord
One thousand eight hundred and sixty-six.
WILLIAM BÜNGER. (L.S.)