Improvement in or relating to Photography in Colours.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvement in or relating to Photography in Colours.
I, JOHN JOLY, Professor of Geology and Mineralogy, of 39, Waterloo Road,
Dublin, do hereby declare the nature of this invention to be as follows:--
In my Patent Number 14161, 1894, I describe a process of colour photography
in which the image consists of minute linear areas overlaid by similar areas in
certain transparent colours. My present invention relates to a mode of rendering
the linear nature of the image less conspicuous. To this end I superimpose upon
the system of linear image and linear colours a linear or other pattern in a trans-
parent medium such as glass or gelatine, this pattern being in relief and
depression on the transparent medium and not consisting of opaque and clear
areas. Thus in the case of a linear transparent pattern I may arrange that the
lines of this pattern shall cross the lines of the photograph obliquely or other-
wise. The effect is to break up the linear image and still preserve--or nearly
preserve its transparency: the result being due to the refraction of light in the
transparent pattern. The transparent pattern may be born on the glass plate
carrying the colours, being etched or otherwise produced on the reverse side. I
may prepare this glass by coating with a protecting varnish and removing this
in places by a sufficiently fine metal comb, the glass then being etched with
hydrofluoric acid. The transparent pattern may be separately superimposed over
the finished transparency. The transparent pattern may be impressed upon the
gelatine carrying the silver image of the positive by steeping this in bichromate
of potash exposing to light under a screen patterned in opaque and clear and
dissolving away the shaded parts in hot water. In order to secure lens-shaped
elevations or depressions I may somewhat separate the opaque and clear screen
from the bichromated gelatine surface or print in diffused light.
The effects of the transparent pattern may be approximately obtained in-
directly in the final picture by any of the following applications of the transparent
pattern; The transparent pattern may be produced on the gelatine of the
negative in the manner last described or the transparent pattern being carried
in a separate plate may be used in the camera being placed in advance of the
taking screen; or it may be etched on the reverse of the taking screen or it
may be used in printing the positive by interposing it between the light and the
negative.

page_text: Improvements in or relating to Photography in Colours.
I, JOHN JOLY, Professor of Geology, of 12, Northbrook Road (formerly of 39,
Waterloo Road), Dublin, 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; -
In my Patent Number 14161, 1894 I describe a process of colour-photography
in which the image is subdivided into minute linear areas overlaid by similar
areas in certain transparent colours. My present invention relates to a mode of
obliterating the linear nature of the image or rendering this linear character
less conspicuous.
To this end I superimpose upon the system of linear image overlaid by linear
colours a minute linear or other pattern in a transparent medium such as glass,
gelatine, celluloid etc.; this pattern being in relief and depression in the trans-
parent medium, and not consisting of opaque and clear areas.
Thus in the case
in which this transparent pattern in relief is linear I arrange that the lines of
this pattern shall cross the lines of the image obliquely or otherwise. The effect
is to break up the linear image and still preserve its full transparency or almost
This result is due to the refraction of the rays passing through the trans-
parent pattern.
SO.
The transparent pattern may be born or impressed on the reverse side of the
transparent plate carrying the colours. Or it may be born or impressed on the
reverse side of the plate carrying the positive photographic image. Or upon a
separate transparent plate which may be affixed to the finished picture or
attached to a stand upon which such picture is viewed, or placed in the carrier
of a projecting lantern.
In order to produce such transparent linear patterns in relief I may proceed
as follows: If it is desired to impress the pattern on gelatine the glass or cellu-
loid support is coated with bichromatised gelatine and then exposed to light
beneath a screen having the required pattern in opaque and clear, whether a
linear or other pattern. Thus a Levy screen may be used. After exposure the
shaded parts are removed by solution in the usual manner. The required pat-
tern now remains. If it is desired to produce the pattern in glass the glass
support treated as above is further treated with aqueous solution of hydrofluoric
acid for a short time and then scrubbed to finally remove the gelatine. The
pattern now appears on the glass.
The pattern may be produced in other ways as by casting the transparent
matterial in a mould having the required pattern in relief: by coating with a
greasy varnish, removing this in a linear pattern by aid of a graver or comb
and then etching with acid or otherwise.
The transparent pattern acts best when raised or depressed in forms which in
cross-section are lens-shaped or rounded. In the mode of procedure described
above for producing the pattern by etching on glass this result is brought about
by the graduated action of the acid through the gelatine. To this end also
slight separation of the Levy screen and the gelatine when printing may in some
cases be advisable.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is-
(1) The combination of a minute transparent pattern linear or other in relief

page_text: and depression in a transparent medium with a linear image in colours, so as to
refract the lines of the coloured image and thereby reduce or annul the linear
appearance of the latter.
(2) The combination of a minute pattern linear or other in relief or depres-
sion on a transparent medium with a transparent linear' image in colours and
either carried on the reverse of the screen bearing the colours or on the reverse
of the positive image, or on a separate plate affixed over the picture or tempor-
arily applicable thereto.
(3) The combination of a transparent plate having a minute pattern raised or
depressed on its surface with a stand for viewing transparent photographs or
with a carrier for projecting the same by aid of a lantern.