IMPROVEMENTS IN PHOTOGRAPHICAL- PORTRAIT APPARATUSES AND OTHER OPTICAL INSTRUMENTS
Year: 1874

page_text: LETTERS PATENT to Frank Wirth, of the Firm of Wirth and Company,
Patent Agency, at Frankfort-on-the-Main, in the Empire of
Germany, for the Invention of "IMPROVEMENTS IN PHOTOGRAPHICAL-
PORTRAIT APPARATUSES AND OTHER OPTICAL INSTRUMENTS." -A communi-
cation from Adolph Steinheil, Doctor of Philosophy, and Edward
Bealed the 25th September 1874, and dated the 31st March 1874.
PROVISIONAL SPECIFICATION left by the said Frank Wirth at the
Office of the Commissioners. of Patents, with his Petition, on the
31st March 1874.
I, FRANK WIRTH, of the Firm of Wirth and Company, Patent Agency,
at Frankfort-on-the-Main, in the Empire of Germany, do hereby declare
the nature of the said Invention for "IMPROVEMENTS IN PHOTOGRAPHICAL
PORTRAIT APPARATUSES AND OTHER OPTICAL INSTRUMENTS," to be as follows:-
These improvements relate especially to photographic lenses or combi-
nations of lenses used for the purpose of taking portraits, and are also
applicable to such lenses or combinations of lenses when used for other
purposes.

page_text: All the best photographic portrait lenses as heretofore constructed and
used consist of three lenses arranged separately, a method of construction
which causes fifteen reflected images, a result most injurious to the
photographic image or picture produced, inasmuch as the light becomes
considerably troubled or disturbed.
Our Invention consists of a novel form and adjustment of the
apparatus by which two lenses only are used, each of which consists of
two parts cemented together. By this method of construction greater
simplicity is obtained, and only six reflected images are produced, and
the resulting photographic image or picture is less injured by the
disturbance of the light.
The most essential advantages however arising from our novel method
of forming and constructing the apparatus are in the much greater speed
with which it operates as compared with the best and clearest lenses
constructed in the methods ordinarily used and practised, and that it
does not admit any distortion of the photographic image even on its
border or edges..
Our novel method of forming photographic portrait lenses is illustrated
in the accompanying Drawing, which is a longitudinal section of the
apparatus, d, d, d³, and d³ being the several parts of the lenses, d and d
being cemented together, and also & and d³.
The curves of the several glasses which compose the lenses differ from
the aplanatic lenses for landscapes and groups as made by us and in
well known and common use, and also from those well known as Dall-
meyer's rectilinear lenses (which also consist of two pairs of cemented
lenses), in not being formed or ground symettrically and alike, but
dissimilar and in such manner that whilst the surfaces R' and R³ have
curves of equal or nearly equal radius, that of the surface R* is shorter
than that of R', and that of R' longer than that, of R. The first and
fourth lenses are made of flint glass and the second and third of crown
glass.
The Drawing illustrates the rule for determining the curves of the

page_text: Sine and mensions sewn in the Drawing are only in
illustration of our Invention, which may be put in practice on a larger
or smaller scale.
By our novel method of forming and arranging the lenses more pure
and undistorted images are formed than by any other method, and it is
applicable not only to lenses for obtaining photographic portraits, but to
lenses for other optical purposes where bright and undistorted images
are required to be produced, the essential points of novelty in our Inven-
tion being the arrangement of two lenses, each of which consists of
two parts cemented together, but which are not formed or ground
symettrically; also the construction of these lenses in such manner that
the surfaces R² and R³. (as shewn in the Drawing) have curves of equal
or nearly equal radius, whilst the curve R' is of shorter radius than that
of R', and that of R' of longer radius than that of R.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Frank Wirth in the Great Seal Patent Office on.
the 30th September 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, FRANK
0 WIRTH, of the Firm of Wirth and Company, Patent Agency, at Frank-
fort-on-the-Main, in the Empire of Germany, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Thirty-first day of March, in the year'

page_text: of our Lord One thousand eight hundred and seventy-four, in the thirty-
seventh year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Frank Wirth, Her special licence
that I, the said Frank Wirth, executors, administrators, and
assigns, or such others as I, the said Frank Wirth, my executors,
administrators, and assigns, should at any time agree with, and no others,
from time to time and at all times thereafter during the term 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 PHOTO-
GRAPHICAL PORTRAIT APPARATUSES
OPTICAL INSTRUMENTS," a
communication from Adolph Steinheil, Doctor of Philosophy, and
Edward Steinheil, persons resident at Munich (Germany), upon the
condition (amongst others) that I, the said Frank Wirth, 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 Scal Patent
Office within six calendar months next and immediately after the date
of the said Letters Patent.
AND OTHER
NOW KNOW YE, that I, the said Frank Wirth, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement and accompanying Drawing (that is to say):
=
These improvements relate especially to photographic lenses or combi-
nations of lenses used for the purpose. of taking portraits, and are also
applicable to such lenses or combinations of lenses when used for other
purposes.
All the best photographic portrait lenses as heretofore constructed and
used consist of three lenses arranged separately, a method of construction
which causes fifteen reflected images, a rosult most injurious to the
photographic image or picture produced, inasmuch as the light becomes.
considerably troubled or disturbed.
Our Invention consists of a novel form and adjustment of the
apparatus by which two lenses only are used, each of which lenses
consists of two parts cemented together. By this method of construction
and arrangement greater simplicity is obtained, and only six reflected

page_text: images are produced, and the resulting photographic image or picture is
less injured by the disturbance of the light.
The most essential advantages however arising from our novel method
of forming and constructing tho apparatus consists in the much greater
speed with which it operates as compared with the best and clearest
lenses constructed in the methods ordinarily used and practised, and that
it does not admit any distortion of the photographic image even on its
border or edges..
Our novel method of forming photographic portrait lenses is illustrated
in the accompanying Drawing, which is a longitudinal section of the
apparatus, d, d', d, and d³ being the several parts of the lenses, d and d
being cemented together to form one lens, and d² and ď³ being cemented
together to form the other lens.
The curves of the several glasses which compose the lenses differ from
the aplanatic lenses for landscapes and groups as made by us and in well
known and common use, and also from those well known as Dallmeyer's
rectilinear lenses (which also consist of two pairs of cemented lenses) in
not being formed or ground symettrically and alike, but dissimilar and
in such manner that whilst the surfaces R³ and R³ have curves of equal
or nearly equal radius, the radius of the surface R' is shorter than that
of R¹ and the radius of R' longer than that of R. The first and fourth
lenses are made of flint glass, and the second and third of crown

page_text: The indices of refraction of the glasses being—
Crown
Flint
-
"
Yellow-benm.
1.51518
1.57402
Violot-beam...
1.52530
1.59010
The particular size and dimensions shown in the Drawing are only in
illustration of our Invention, which may be put in practice on a larger
or smaller scale.
By our novel method of forming and arranging the lenses more pure
and undistorted images are formed than by any other method, and it is
applicable not only to lenses for obtaining photographic portraits, but to
lenses used for other optical purposes where bright and undistorted 1
images are required to be produced.
Having now described our Invention and the manner in which it is to
be performed, we claim the arrangement of two lenses, each of which
consists of two parts cemented together, but which are not formed or
ground symettrically, substantially as and for the purposes described; 1
also the construction of these lenses in such manner that the surfaces R³
and R³ (as shewn in the Drawing) have curves of equal or nearly equal
radius, whilst the curvo R is of shorter radius than that of R', and that
of R³ of longer radius than that of R, substantially as described and
shewn in the Drawing..
In witness whereof, I, the said Frank Wirth, have hereunto set
my hand and seal, this Twenty-first day of September, in the
year of our Lord One thousand eight hundred and seventy-
2