Improvements in Half-tone Negatives for Photo-mechanical Processes.
Year: 1893

page_text: Date claimed for Patent under Sect. 103 of Act,
being date of first Foreign Application (in 28th Mar,
United States of America),
ate of Application (in United Kingdom). 27th Oct., 1893
1893
Complete Specification Left. 27:h Oct., 1893-Accepted, 21st Apr., 1894
⚫ate of Application (in United Kingdom). 27th Oct., 1893
Complete Specification Left. 27:h Oct., 1893-Accepted, 21st Apr., 1894
COMPLETE SPECIFICATION.
Improvements in Half-tone Negatives for Photo-mechanical
Processes.
I. FREDERICK JOHN MATHEW GERLAND, of Bayonne in the County of
Hudson, and State of New Jersey, and also of 26-30 Vesey Street, New York
City, New York, U.S.A. Photo Engraver, 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:-
This invention relates to photo-engraving and printing processes and its object
is to provide a new and improved negative which has the film on the sensitive plate
so treated by the action of the admitted light as to improve the fiual result over
existing methods, and to produce a half-tone negative having the film in the high
lights treated by a photographic chemical process to form non-printing spaces
which would otherwise have to be cut out of the film by hand or touched or
printed out on the ordinary negative.
The invention consists of a half tone negative having the film in the high lights
photographically and chemically obliterated to form non-printing spaces in the
negative.
In preparing negatives for photo processes as heretofore practiced, the screen
was employed in front of the sensitive plate during the time of the exposure so that
the negative. image of the subject under treatment was formed in dots or lines on
the sensitive plate. By this former process no pure, white spaces could be
produced in the final prints without injury to the general appearance of the picture,
and consequently the prints thus obtained from the finally finished negative, had a
flat appearance.
In order to photographically produce a negative having full-tones, half-tones
and clear spaces in the high lights, various processes may be employed, I prefer,
however, the following process. I divide the full exposure into periods of time,
during one of which the sensitive plate is subjected to a partial exposure without
a screen, and in the other the screen is introduced between the lens and plate. In
the first period a sufficient exposure is had so that the high lights from the lighter
parts of the object to be reproduced in passing through the lens on to the sensitive
film, deaden the latter in places corresponding to the lighter parts of the object;
and hence render these places non-sensitive for further deposit of light. In the
second period, dots or lines for the relief plate are produced on the dark parts and
half-tones of the subject under treatment, and the semi-tones of the first exposing
period are not further disturbed, but remain true according to the subject. As
the sensitiveness of the film has been destroyed by the light in the high lights,
the said part of the plate is not affected by the screen, and consequently no dots
whatever are formed in those places, and consequently the negative contains pure
white spaces, half-tones and all gradations of the copy or subject. After the full
exposure is made, the exposed sensitive plate is then developed, fixed and dried in

page_text: the usual manner to prepare the plate for printing. It is not essential that the
screen be used in the second period, and an unobstructed exposure be had in the
first period, as this order may be reversed, and the screen used in the first period and
an unobstructed exposure made in the second period. By the method described, a
negative is produced which has a uniform tone in the high lights, which tone
produces a clear or non-printing space in the positive print on the stone, zinc or
copper plate, so that the finished print shows clear white spaces in the high lights,
corresponding to the light places on the object photographed. It is well known
that this work of removing whites from the stone or plate, had, formerly, to be
done by the artist, with the aid of suitable tools or acids, or the artist touched up
the negative.
Having now particularly described and ascertained the nature of this inven-
tion, and in what manner the sume is to be performed, I declare that what I
claim is :-
1. As a new article of manufacture, a half tone negative having the film in the
high lights of the plate photographically and chemically treated for forming non-
printing spaces in the positive, substantially as shown and described.
2. The herein described process of producing half-tone negatives for photo-
processes, consisting in subjecting a sensitive plate to a part of the time for a full
exposure without a screen, and for the remainder of the time of the full exposure
with a screen, between the negative and object, substantially as described.
Dated this 27th day of October 1893.
FELL & WILDING,
Agents for the Applicant.