Improvements in the Art of Making Half Tone Plates.
Year: 1899

page_text: Date of Application, 8th Aug., 1899
Complete Specification Left, 5th May, 1900-Accepted, 4th Aug., 1900
PROVISIONAL SPECIFICATION.
Improvements in the Art of Making Half Tone Plates.
-
I, JOHANNES GIESECKE, of Nurnbergerstrasse 12, Leipzig, Germany, Printing
Office Manager, do hereby declare the nature of this invention to be as follows:-
Hitherto, in making half tone plates by the photo-mechanical process the line-
ruled or dotted screen is placed within the photographic camera and in proximity
of the sensitive plate. By these means, the screen negative obtained on the
latter will be a copy on an unvaried scale of the original screen, and therefore
screens of different width of net are to be used for producing half tone plates of
different size and density of grain, a screen, moreover, of full the size of the half
tone plate to be produced being needed in each case.
The inconveniences arising therefrom fully appear when reproducing the
original on an enlarged scale as for obtaining the best result in each case the
width of the screen net to be used must be in proportion to the respective scale
of enlargement, thus necessitating to purchase a large set of large screens.
The object of my invention is to remove the said inconveniences and to pro-
vide means by which half tone plates of any size and of any grain size can be
produced by using only one and the same standard screen.
I attain these objects by projecting (instead of copying) the said standard
screen on the sensitive surface and thereby enlarging or reducing, as the case
may be, the width of its net in the proportion desired, and at the same time
substituting for the given original to be produced a negative (or a diapositive)
taken therefrom on a suitably enlarged or reduced scale.
To carry my invention into effect, I place my standard screen out of the
camera at a point between the lense and the source of light, and I adjust the
screen with respect to the sensitive camera plate so as to obtain on the latter a
projection of the screen net in full sharpness and of the width desired.
Having thus fixed the place of my screen, I take a negative from the original
to be reproduced, the scale of this negative being so calculated that its projection
on the sensitive camera plate will appear in the size intended for the half tone, if
the said negative is placed in suitable proximity of the screen adjusted as
heretofore described.
In order to easily have the scale needed for the negative a tabulated statement
may be made use of, containing once for all the several cases which may arise.
The said negative (or if needed a diapositive taken therefrom by copying the
same) is to be used in my invention instead of the original given.
Having again adjusted my screen to its place as described, I now place the
above negative (or diapositive) in proximity of the screen at the point for which
its size has been calculated (this point being preferably chosen between the
screen and the source of light, or in other words beyond the screen with respect
to the camera). The photograph is then taken as usual, and a negative thus will
be obtained on the sensitive camera plate, corresponding to the size required and
provided with a net of the width desired.
In the case of half tone plates being to be reproduced to correspond at the

page_text: same proportion, as to their size and the size or density of their grain, to the
size of the screen and the width of its net, the use of a separate screen can be
dispensed with, and a line ruled negative (or diapositive) can be made use of.
To this purpose, I adjust my standard screen as heretofore described, calculating,
however, the scale of the negative (or diapositive) so that it will appear on the
sensitive plate in the size required, if substituted for the screen in its adjusted
position. The negative (or diapositive) then being taken on the said scale, the
standard screen is copied on the same, and a photograph is taken from the line
ruled negative (or diapositive).
By using suitable blinds, the character of the screen net projected on the
sensitive plate can be differently varied.
In order to finally obtain the well known half tone plate for typographic
printing the negative or diapositive plate is copied on a metal plate and the
latter etched as usual.
Another kind of half tone plate, say for lithographic printing, can be obtained
by directly copying the sensitive plate on a stone or a zinc plate, or by copying
the same on a sensitive transfer paper and then transferring the copy to the stone
or the zinc plate. By printing therefrom half tone lithographs are obtained
showing fully the character of typographic prints.
1000
H. GARDNER,
Patent Agent, 166, Fleet Street, London,
Agent for the said Johannes Giesecke,
I, JOHANNES GIESECKE, of Nurnbergerstrasse 12, Leipzig, Germany, Printing
Office Manager, 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:―
Hitherto, in making half tone plates by the photo-mechanical process the line-
led or dotted screen is placed within the photographic camera and in proximity
of the sensitive plate. By these means, the screen-negative obtained on the
latter will be a copy on an unvaried scale of the original screen, and therefore
screens of different width of the net are to be used for producing half tone plates
of different size and density of grain, a screen, moreover, of full the size of the
half tone plate to be produced being needed in each case.
The inconveniences arising therefrom fully appear when reproducing the
original on an enlarged scale, as for obtaining the best result in each case the
width of the screen net to be used must be in proportion to the respective scale
of enlargement, thus necessitating to purchase a large set of large screens.
The object of my invention is to remove the said inconveniences and to provide
means by which half tone plates of any size and of any grain size can be pro-
duced by using only one and the same standard screen.
I attain these objects by projecting (instead of copying) the said standard
screen on the sensitive surface and thereby enlarging or reducing, as the case
may be, the width of its net in the proportion desired, and at the same time
substituting for the given original to be reproduced a negative (or a diapositive)
taken therefrom on a suitably enlarged or reduced scale.
To carry my invention into effect. I place my standard screen out of the
camera at a point between the lense and the source of light, and I adjust the screen

page_text: with respect to the sensitive camera plate so as to obtain on the latter a pro-
jection of the screen net in full sharpness and of the width desired.
Having thus fixed the place of my screen, I take a negative from the original
to be reproduced, the scale of this negative being so calculated that its pro-
jection on the sensitive camera plate will appear in the size intended for the
half tone, if the said negative is placed in suitable proximity of the screen
adjusted as heretofore described. In order to easily have the scale needed for
the negative, a tabulated statement may be made use of, containing once for all
the several cases which may arise. The said negative (or if needed a diapositive
taken therefrom by copying the same) is to be used in my invention instead of
the original given.
Having again adjusted my screen to its place as described, I now place the
above negative (or diapositive) in proximity of the screen at the point for which
its size has been calculated (this point being preferably chosen between the
screen and the source of light, or in other words beyond the screen with respect
to the camera). The photograph is then taken as usual, and a negative thus
will be obtained on the sensitive camera plate, corresponding to the size required
and provided with a net of the width desired.
In the case of half tone plates being to be produced to correspond at the same
proportion, as to their size and the size or density of their grain, to the size of the
screen and the width of its net, the use of a separate screen can be dispensed
with, and a line ruled negative (or diapositive) can be made use of. To this
purpose I adjust my standard screen as heretofore described, calculating, how-
ever, the scale of the negative (or diapositive) so that it will appear on the
sensitive plate in the size required, if substituted for the screen in its adjusted
position. The negative (or diapositive) then being taken on the said scale, the
standard screen is copied on the same, and a photograph taken from the line
ruled negative (or diapositive).
By using suitable blinds, the character of the screen net projected on the
sensitive plate can be differently varied.
In order to finally obtain the well known half tone plate for typographic
printing the negative on the sensitive plate is copied on a metal plate and the
latter etched as usual.
Another kind of half tone plate, say for lithographic printing, can be obtained
by transferring the picture from the sensitive camera plate to a stone or a
zinc plate, the said stone or zinc plate then being prepared as usual in litho-
graphy. By printing therefrom half tone lithographs are obtained showing
fully the character of typographic prints.
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. In the production of lithographic or typographic half tone plates by means
of a screen, the art of making such plates of any size and of any density of
grain or width of network, by means of but one and the same standard screen,
which consists in adjusting the screen out of the camera at a point so as to
obtain on the sensitive camera plate a sharp projection of the screen net on the
scale desired, taking a negative (or a diapositive) from the original to be repro-
duced, on a scale so as to appear on the sensitive plate in the size intended if
placed in suitable proximity of the screen, placing the said negative (or dia-
positive) at the point for which its size has been calculated, preferable beyond the
screen with respect to the camera, and photographing both, the screen and the
negative (or diapositive), on the sensitive plate substantially as and for the pur-
poses described.
2. In the production of lithographic or typographic half tone plates by means
of a screen, the art of making such plates of any size and of any density of
grain or width of network, by means of but one and the same standard screen,

page_text: which consists in adjusting the screen out of the camera at a point so as to
obtain on the sensitive camera plate a sharp projection of the screen net on the
scale desired, taking a negative (or diapositive) from the original to be repro-
duced, on a scale so as to appear on the sensitive plate in the size intended if
brought at the place of or substituted for the screen, and copying the standard
screen on the negative (or diapositive) when taking the same, substituting the
said line ruled negative (or diapositive) for the screen, and photographing the
line ruled negative (or diapositive) on the sensitive camera plate, substantially
as and for the purposes described.
3. Lithographic or typographic half tone prints obtained from half tone plates
of the kind described.