Improvements in Photographic Apparatus on the Pinhole Air Lens Principle.
Year: 1892

page_text: Date of Application, 26th July, 1892
Complete Specification Left, 15th Apr., 1893-Accepted, 26th July, 1893
PROVISIONAL SPECIFICATION.
Improvements in Photographic Apparatus on the Pinhole Air Lens
Principle.
I ARCHIBALD CAMPBELL PONTON of Viewfield, Parkstone, in the County of
Dorset, Architect, do hereby declare the nature of this invention to be as
follows:-
The invention relates mainly to the construction of cameras for taking pictures
rapidly through very small pinhole lenses the focal lengths of the air lens or
what is the same the depth of the camera being apportioned to the rapidity
of exposure. I find that I may use pinholes as small even as 50 of an inch in
diameter. These may be formed in metal foil such for instance as of platinum.
The latter may
or brass and are inserted in the lid of a box-shaped camera.
be made of card board or sheet metal and may be pressed up. The interior size
of the camera should be that of sensitized plate to be used and of the depth
of the focus of the air lens. I prefer to make the camera in two parts onc
fitting into the other like the ordinary card board box in which sensitized plates:
are sold. The box lid may by partition or partitions be divided into two or four
compartments for the production of several photographs on one sensitized plate
thus for instance adapting it for sterescopic pictures. On the outside or inside
of the lid I provide a movable levershaped or other shutter which for two pinholes
for stereos may be T shaped and working on a pivot.
This apparatus may be made so light as to only slightly exceed the weight of
the plates themselves at the same time it can also be made at a very low price
indeed so as to bring it within the reach of the million.
From the small negatives produced by this apparatus the positives can be
printed in an enlarging camera of the size most suited for trade purposes..
Negatives taken with an air lens of Too of an inch in diameter for sterescopic
pictures are found to give a sufficient field to be printed from direct by contact.
Taikin 20th day of July 1892.
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.
COMPLETE SPECIFICATION.
Improvements in Photographic Apparatus on the Pinhole Air Lens
Principle.
I, ARCHIBALD CAMPBELL PONTON of Viewfield, Parkstone, in the County of
Dorset, Architect, do hereby declare the nature of this invention and in what
manner the same is to be performed to be particularly described and ascertained
in and by the following statement:-
The object of this invention is to lessen the price of cameras with pinhole or air
lenses, and to diminish the time of exposure so as to make them available for
portraiture while they are also applicable for architectural and other views.
Heretofore it has been considered that holes of a less diameter than oths of an
inch or ths of a millimetre were unsuited for correct photographic images but I
have by extensive experiments not found any such restriction and I have on the
contrary found that holes oths of an inch or gth of a millimetre in diameter or
less give a good photographic image. It has also been considered that for each

page_text: sized hole there was a shortest focus giving the most rapid exposure at a distance
where it was calculated that the phase of the wave length of light from the edge of
the hole first coincided with the phase of the wave length from the centre of the
hole but I have found there is no such restriction and that at shorter foci a good
and more rapidly exposed photographic image is obtained, where the phases of the
wave lengths of light do not coincide. These observations have led to the
following construction of cameras without the ordinary glass lenses. For small
cameras such as those having a focus of less than 4 inches 1 adopt the following
construction. A pasteboard, thin wood, metal or other suitable opaque material is
used for the parts and pressed up or otherwise formed into box shape.
A box is made capable of containing the sized plate which is intended to be used
as for example a plate 41 x 31 inches. Figure 1 of the accompanying drawings is
a full size front view of such a camera, Figure 2 a vertical longitudinal section,
Figure 3 face view of an interior part containing the pinhole lenses, Figure 4 face
view of back of camera proper, Figure 5 inside face view of the box lid, and Figure 6
perspective view of the camera. This box A A' has its sides A' about equal to the
focal length say about 2 inches. The inside of the box A A' is lined with black
velvet, or black paper which does not reflect light and the sides A' are similarly
covered on the outside. Another box B B with sides B1 exactly equal to the
focal length is constructed a little smaller than the surface of the sensitized
plate C. This box fits inside the box A A' so that the sides B' when pushed down
will touch the sensitized plate Call along the external edges and keep it fixed
against the end A of the box A A¹. The box B B carries a thin metal plate E
movable on a fulcrum pin E' and a band F of very thin metal is fixed thereto
having the holes F' F' suited for the focus. For the band F is used hard metal
foil about roof an inch in thickness, or much less even, if obtainable. The
box B B is lined both inside and out with black paper or velvet. The lid D, DI
is made with sides D' of nearly the length of the focus. This lid is also lined with
a black non-reflecting material on the inside. The front D of the lid D D' on its
inside face supports a thin metal triangular-shaped shutter G which is movable ou
a centre pin G and has a hole G' so that moving in one direction it both uncovers
and covers the pinhole. The side parts B' ensure absolute darkness inside. When
the part B is omitted and the parts 131 are fixed direct to the part D, the pinhole
piece E is pivoted to the inside of D and the shutter G to the outside of D. The
box B B carrying the pinholes F1 F2 has its front part B so made as to fit well in
the box lid D D carrying the shutter G as these two boxes need only to be
separated for the examination of the working parts of the camera. A peg E² or
a cord is used to move the plate E with the hole For F, which it is intended to
use, into its position from the front face of the camera and a peg G³ or a cord is
used to move the shutter G. These pegs or cords E and G³ project from the face
of the camera through suitable slots D2 and D³ giving the requisite play of the
movable parts, stops being provided at D* D*. The camera is secured to the top I
of the stand by a rubber band H.
The box B B may by a partition or partitions be divided into two or four
compartments for the production of several photographs on one sensitized plate
thus for instance adapting it for stereoscopic pictures. On the inside or outside of
the lid D D' I provide a movable lever-shaped or other shutter which for two
pinholes may be T-shaped worked on a pivot. For four pinholes I may use two
such shutters connected by a rod.
This apparatus may be made so light as to only slightly exceed the weight of the
plate at the same time it can also be made at a very low price indeed so as to bring
it within the reach of the million.
From the small negatives produced by this apparatus the positives can be printed
in an enlarging camera of the size most suited for trade purposes.
Negatives taken with a pin-hole lens of 10 of an inch in diameter for stereo-
scopic pictures are found to give a sufficient field to be printed from direct by
contact.

page_text: In forming the holes to admit the photographic image I prefer to use very thin.
metal at least less than Toth of an inch in thickness in a narrow band of about
of an inch wide and I insert the number of holes which I intend to use at
distances of about of an inch apart and I employ the diameters of the holes in
the geometrical ratio in the series of 1, 2, 4, 8 and 16. The most convenient size
to start from is th of a millimetre equal to about 5th of an inch.
plate cameras of about 2 inches focus I employ the holes ths and ths of a
For quarter.
millimetre in diameter the former requiring an exposure of about 16 seconds and
the latter of about one second, but in cameras of about 4 inch focus and beyond
that focus covering larger plates than quarter size I prefer to introduce the hole of
1th of a millimetre diameter, in addition to the holes 2, 4, 8 and 16 tenths of a
millimetre in diameter. Thus I can obtain variety of exposure and texture or
definition and the expense of having 5 holes in lieu of one is too slight to be of
consideration whereas the advantages of the range of holes are very great. The
body for these larger cameras may be of the ordinary bellows, folding or collapsing.
structure.
The metal plate to carry these holes is formed of a triangular-shaped thin piece.
of metal similar to that shown at E Fig. 3, the apex of the triangle forming the
index pointer the base of the triangle being pierced with as many holes as it is.
intended to employ and the strip of very fine metal with the holes accurately
pierced is attached to this metal plate so that the fine holes are exactly opposite to.
the holes pierced in the metal plate. On the front of the camera there is a slit
and a peg or a cord is passed through the slit and attached to the apex of the.
metal plate. Along the edge of this slit are marked figures and these figures
correspond to the relative exposures required for each hole for one fixed focus
either in seconds or minutes. For example in a camera where the fixed focus.
would be about 16 inches the figures showing the relative exposures are minute,.
1 minute, 4 minutes, 16 and 64 minutes and when the index is opposite one of these
figures, then one of the holes is in its proper place. These holes can be shifted
into position when the sensitized plate is in the camera and used as occasion requires..
I use for each size camera and plate a construction such as described and with a
certain fixed focus. These focal lengths are determined according to a certain law
which I have discovered and which is illustrated by the ten times enlarged diagram
Figure 7. The pin hole at A is say one millimetre. The lines C and C¹ drawn
from opposite edges of the pin hole to the division points on what represents the.
sensitized plate B cross each other at distances of 4, 8, 16 and 32 mm. These lines.
represent the axes of vibration of the light waves. The numbers 4, 8, 16, 32 and
so on to 2048, I find should be the ratio of the fixed foci. Beyond 2048 the time.
of exposure becomes too great for practical photography. For large size cameras
I may vary the focal length by expanding the camera to different fixed focal
lengths in the ratio named and use stops or notched bars to determine these lengths.
As an example if I take 1 mm. for the diameter of the pin hole 1 find that I
obtain a good picture at a focus of 16 inches, or of 8, 4, 2, 1, 4, 4, and inch: in
like manner if I take 18 mm. for the diameter of the pin hole I can obtain a good
picture at about 2 inches focus (as shown at Fig. 2) or at 4, 8, 16, 32, 64 inches.
and so on. I use pin holes varying from 1 to 16 parts of a millimetre in diameter.
n geometrical ratio for the holes, yet all with one fixed focus, and I obtain a
picture with as rapid an exposure as I may require as for instance of a second
for a hole millimetre in diameter and with about half an inch focus.
can,
Having now particularly described and ascertained the nature of my said inven-.
ion and in what manner the same is to be performed I declare that what I
claim is :-
1. A pin hole camera consisting of a box A A' for receiving a sensitized plate.
nd a lid D D' provided with one or more pin hole lenses and a shutter or shutters
nd having inner walls B₁ for holding the plate at the proper focal distance in the
amera and for excluding the light substantially as set forth.

page_text: 2. The construction of pin hole camera with pin hole and shutter arrangement as
described with reference to the drawings.
3. Constructing pin hole.cameras with the focal lengths and pin holes as and in
the relative ratios described.
Dated this 15th day of Anril 1893
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.