NEW APPARATUS FOR THE EXPOSING OF PHOTOGRAPHIC SENSITIVE PLATES in Cameras and Reversible Camera
Year: 1884

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We JOHN and ALFRED GEORGE HOPKINS of Amwell Cottage, Hoddesdon in the
County of Herts, Photographers, do hereby declare the nature of our Invention
for A NEW APPARATUS FOR THE EXPOSING OF PHOTOGRAPHIC SENSITIVE PLATES
in Cameras, and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
Our Invention as above, to be designated hereafter as the Simplex Slide and
Reversible Camera Back, consists of a perfectly light-tight box or slide, made so as
to receive the sensitive plate in a carrier, which said carrier is made to run in
grooves in slide, and which cannot get displaced when putting in or taking out
plats; this said slide is made perfectly impervious to light by means of a simple
lid affixed to the plate carrier, in such a manner that when the said carrier
containing sensitive plate is pushed home into the slide, and by means of a simple
turn of screw let in on top of slide, into a screwed plate on plate carrier to keep it
fixed, it becomes perfectly proof against light. The camera back is so made, with
an opening on top the exact size of the plate slide, which when exposure is to be
made, it is fixed thereto by means of two levers each side of back in-erted in small
grooves ma le in plate slide, which by this means makes the whole perfectly rigid.
The exposure of plate is made by simply removing the small screw on top of al de,
and inserting a rod with screw at end, so as to screw into plate carrier, by which
means the plate is let down or drawn up at will of operator; the said rod to be
just the length of slide, so that by simply pushing the plate carrier down in grooves
into the said back, the sensitive plate is kept in position by means of a spring
which is attached to back of plate carrier, the plate is then ready for exposing.
The camera back is made with a door, so that the focusing screen, can be inserted
or taken out without interfering whatever with plate slide when attached to
camera back, so that the focusing of a subject, and exposure of plate on same
becomes a most simple and very easy method, and very quickly done.
Having now particularly described and ascertained the nature of our said
Invention and in what manner the same is to be performed, we declare that what
we claim is ;-
1st The plate carrier, with spring back, and light tight lid affixed.
2. The slide or box to receive plate carrier.
3. The arrangement of rod with screw end passing through top of slide into a
screw plate on carrier for bringing into position the sensitive plate into

page_text: 4. The arrangement of the screw passing through top of slide into screw plate of
carrier, for keeping slide impervious to light when closed.
5. Reversible camera back, made with an opening to receive plate slide.
6. Levers on camera back, for making slide quite rigid when brought into
grooves of slide.
7. Method of inserting focusing screen into camera back without interfering
with slide while attached to the back.
8. The camera back can be made to fit any camera, and any number of slides
can be used with same.
JOHN HOPKINS.
ALFRED GEORGE HOPKINS.