IMPROVEMENTS IN PORTABLE SKETCHING CAMERA OBSCURAS
Year: 1869

page_text: PROVISIONAL SPECIFICATION left by Henry Turner Munns at the
Office of the Commissioners of Patents, with his Petition, on the
22nd June 1869:
I, HENRY TURNER MUNNS, of Birmingham, in the County of
Warwick, Artist, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN PORTABLE SKETCHING CAMERA OBSCURAS," to be as
follows:-
My Invention consists of the improvements herein-after described in
portable sketching camera obscuras, by which improvements great
facility and convenience in sketching from nature are obtained, com-
bined with great portability and lightness.
In order that my Invention may be the better understood, I remark that
a portable sketching camera obscura consists essentially of a tripod stand
having a covering or tent for the exclusion of light and wet, the said
tripod stand supporting at its top a lens, the axis of which is vertical;
above the said lens is a mirror inclined at an angle of 45 degrees to the
axis of the lens, and capable of rotating about the said axis. The
landscape reflected from the mirror to the lens is delineated by the said
lens upon a horizontal sketching table within the tripod stand.

page_text: My improvements are as follows:-The lens is carried by a box fixed
to the triangle of the tripod stand, the said lens being hinged to the
lower side of the box, so that it can be turned down for the purpose of
wiping it. The mount of the lens is screwed externally and takes into
a concave screw in the box; by means of the said screws the focussing of
the picture is effected. The said lens box is capable of a sliding motion
for the purpose of adjusting the position of the picture upon the
sketching table. The mirror is made to slide in the frame without.
changing its angle so as to bring the tops of very high objects into the
picture when requisite. 1 make the covering or tent. for excluding light
and wet of light coloured macintosh or waterproof cloth. I make one or
more small hoods in the covering or tent for the purpose of ventilation,
and make a tube of the said waterproof cloth at one side or other
convenient part of the tent in order when requisite to admit light upon
the sketching table, so that the sketching of the landscape may be
proceeded with, either wholly in the dark or partly in daylight, at the
will of the sketcher. That part of the tent under which the sketcher
sits is made in the form of a hood, the lower part being distended
by steel springs, and the upper part hung to a small horizontal rod
inserted in the before-mentioned triangle by means of pulleys on the
lens box, over which cords attached to the bamboo cares are passed. The
sketcher when inside the tent can raise the hood, which hood on pulling
the said cords rises somewhat after the manner in which the external
sun blinds of windows rise. The tent is supported by the waterproof
cloth being fitted in a groove in the triangle. When it is required to
pack the tent it is only necessary to remove the horizontal rod sup:
porting the upper part of the hood when the said hood collapses, and
may be packed within the tripod. The sketching table is supported
vertically by tapes having a series of eyalet holes, into which hooks at
the angles of the table may be inserted. The said table is supported
horizontally by means of three ball and socket joints, the ball part of
each joint being connected to the said table, and the socket part. being
inserted in the legs of the tripod stand. The said sockets are divided,
the two parts being held together by a spring, and the ball part of the
joint by slight pressure can be made readily to spring into or out of the
socket part in putting up or taking down the instrument. The balls are
not connected directly to the sketching table, but are fixed on the ends
of short rods connected with the table. By this arrangement con-
siderable vertical motion is permitted in the table, while horizontal

page_text: motion is prevented. In order to exclude light from below the sketching
table carrics on its under side a sliding board, which can be drawn out
to come against the sketcher, and thereby exclude bottom light. The
said sliding board may also be used as an easel. The tripod legs are
made of rods square in cross section, but are divided about half way
down, the division being made diagonally, so that each of the divided
parts is triangular in cross section and very rigid.