IMPROVEMENTS IN PHOTOGRAPHIC OBJECTIVES
Year: 1881

page_text: LETTERS PATENT to Hugo Adolph Steinheil, of Munich, in the Kingdom of
Bavaria and Empire of Germany, for an Invention of "IMPROVEMENTS IN
PHOTOGRAPHIC OBJECTIVES."
PROVISIONAL SPECIFICATION left by the said Hugo Adolph Steinheil at
the Office of the Commissioners of Patents on the 12th April 1881.
.
HUGO ADOLPH STEINHEIL, of Munich, in the Kingdom of Bavaria and Empire
of Germany. "IMPROVEMENTS IN PHOTOGRAPHIC OBJECTIVES."
Double objectives can be readily so constructed as to give images on plane
surfaces, but the distinctness of such pictures decreases from the centre towards
the edge more or less rapidly according as the construction is less or more perfect.
Any real improvement of the image in this respect requires a construction of the
objective totally different from that at present in use.
I have found by extensive calculations that a double objective will give images
that are the more clear towards the edge the more unequal are the division of
the properties of the compound objective between the two single objectives
(combinations).
In the antiplanetic objectives (avri, opposed, havao, to deviate therefore,
composed of semi-objectives with opposite deviations), which form the subject of
my present Invention, the two combinations are very dissimilar in respect of focal
length and errors, and they are calculated for two different purposes; first, for
operating in the open air, such as for groups, landscapes, and the like, in which, on
account of the reflexes, no more than two separated lenses can be used (4 refractions
from air into glass or from glass into air), and consequently in which the lenses
forming each combination must be cemented together; second, for operating in the
studio, where large openings in comparison to the focal lengths are necessary, but
where, on the other hand, the lenses of the one combination may be separated from
each other.
In constructing a lense according to the first method it has, with a focal length
of 240mm. (9-46ins.), an opening of 43mm (1·69ins.) for both combinations. The
front combination, upon which the light falls consists of a bi-convex flint glass
lense cemented to a bi-concave crown glass lense, which combination has a focal
length of about 216mm. (8.5ins.) and has strongly chromatic and spherical aberrations,
and also produces strongly curved images in the same sense as a simple positive
lense. The second combination, which is at a slight distance from the first, consists

page_text: of a bi-concave flint glass lense cemented to a bi-convex crown glass lense, and has
a very long negative focal length, as also strong spherical and chromatic
aberrations, but in the contrary sense to that of the other combination, the errors
of which are consequently neutralised thereby.
The descriptions of glass used are:-
R₁287.8mm.
R
Distance between the two combinations, d
98.4mm. crown d₁ = 4.1mm.
= 4.1mm.
Rug
=
98.4
R₁
= 34.44
light flint ds
= 3.28mm.
Rg + 72-1
crown- d₁ = 24.6mm.
Fig. 1 of the accompanying Drawing shews the above described objective partly
in elevation and partly in section.
In constructing a lense according to the second method it has for the same focal
length of 240mm. an opening of 76.25mm for the front combination. The rear
combination consists of two lenses of unequal size separated from each other, the
one being a flint lense of 46-4mm. opening, and the other a crown glass lense
of 58.8mm opening. The front combination of which the first radius of curvature
is very short has a positive focal length of 156mm, and consists of a bi-convex
crown lense cemented to a bi-concave flint lense, and has also strong chromatic and
spherical aberration, and gives a strongly curved image in the same sense as a
simple positive lense possesses these faults. The rear combination, which is at a
distance of about one third of the opening of the front lense, consists of a bi-concave
flint lense and a bi-convex crown lense, the latter being at a distance from the
former equal to about one fourth of the opening of the rear lense.
This rear
combination has a negative focal length of 777, and has also strong chromatic
and spherical aberration and gives a strongly curved image, but in the contrary
sense to that of the front combination, that is, in the same sense as the faults of a
simple negative lense. The compound objective is therefore composed of a
non-compensated positive objective and of an over-compensated negative objective.
The description of glass used are the same as given for the first contruction.
d n¹
= 1.6304mm.
The necessary elements for constructing this instrument with the same focal
length of 240mm and 76-25m opening are as follows:-
(R = + 72.24mm. )

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Hugo Adolph Steinheil in the Great Seal Patent Office on
the 11th October 1881.
HUGO ADOLPH STEINHEIL, of Munich, in the Kingdom of Bavaria in the Empire
of Germany. "IMPROVEMENTS IN PHOTOGRAPHIC OBJECTIVES."
Double objectives can be readily so constructed as to give images on plane
surfaces, but the distinctness of such pictures decreases from the centre towards
the edge more or less rapidly according as the construction is less or more perfect.
Any real improvement of the image in this respect requires a construction of the
objective totally different from that at present in use.
I have found by extensive calculations that a double objective will give images
that are the more more clear towards the edge the more unequal are the divisions
of the properties of the compound objective between the two single objectives
(combinations).
In the antiplanatic objectives (ar, opposed, havao, to deviate therefore,
composed of semi-objectives with opposite deviations), which form the subject of
my present Invention the two combinations are very dissimilar in respect of focal
length and errors, and. they are calculated for two different purposes; fiirst, for
operating in the open air, such as for groups, landscapes, and the like, in which,.
on account of the reflexes, no more than two separated lenses can be used
(4 refractions from air into glass or from glass into air), and consequently in which
the lenses forming each combination must be cemented together; second, for
operating in the studio where large openings in comparison to the focal lengths are
necessary, but where on the other hand the lenses of the one combination may be
separated from each other.
In constructing a lens according to the first method it has, with a focal length of
240 (9.46 ins.), an opening of 43mm. (1.69 ins.) for both combinations. The front
combination upon which the light falls consists of a bi-convex flint glass lens cemented
to a bi-concave crown glass lens, which combination has a focal length of about 216mm.
(8.5 ins.), and has strongly chromatic and spherical aberrations, and also produces
strongly curved images in the same sense as a simple positive lens. The second com-
bination, which is at a slight distance from the first, consists of a bi-concave flint glass
lens cemented to a bi-convex crown glass lens, and has a very long negative focal
length, as also strong, spherical, and chromatic aberrations, but in the contrary sense
to that of the other combination, the errors of which are consequently neutralised
thereby.
The descriptions of class used ore.

page_text: H. A. STEINHEIL. (L.S.)