Year: 1898

page_text: I, KICHARD WILLIAM ARTLETT, of 38, Alexandra Road, Richmond, in the
County of Surrey, Photographer, do hereby declare the nature of this invention
to be as follows:-
This invention relates to improved means applicable for use in photographing
pictures and other objects presenting a variety of colours, the actinic properties
of the different colours presented by the object being modified to a greater or
less extent according to the relative positions in the spectrum of the several
colou18. With the aid of my invention, not only are the various shades or
descriptions of colour represented by appropriate half-tones, but from an artistic
point of view a far more accurate results obtained than by the means hitherto
commonly employed.
As 18 well known, the silver compounds used in the preparation of photographic
plates or films are extremely sensitive to the violet and ultra-violet rays while
they are much less sensitive to the green and very much less so to the red rays,
although these two latter make up the most luminous portion of the spectium
Visually
Plates specially prepared for orthochromatic photography have, by chemical
means, been rendered more sensitive to the red and very much more sensitive
to the green rays, but they are still so much less sensitive to those lays than
they are to the lays at the violet end of the spectrum that, to obtain anything
like a correct rendering of an object comprising various colours, I cause the light
from the object to pass through a coloured screen which stops a due proportion
of those rays which act too energetically on the sensitive film In preparing this
sci een I employ two discs of glass which preferably have plane surfaces but may
be ground to a slight curvature Each of these 18 coated on one side with a film
of gelatine, collodion or other suitable material and each film is then dyed,
the one a strong bight yellow, and the other a clear strong ied. The yellow dved
film permits the red, yellow and green 1ays to pass and intercepts the whole or
nearly the whole of the blue rays; whilst the red-dyed film operates to intercept
the violet, indigo, blue and green rays In the centre of the vellow film, there
is a small circular vacant space, and in the centre of the red film there is a
comparatively large cncula vacant space The two discs are now cemented
together, film to film, with Canada balsam or other cement having a refractive
power corresponding as nearly as may be with that of the gellatine or collodion
film.
A screen prepared in the manner above described transmits a small quantity
of the very energetic blue and violet rays (along with the other rays constituting
white light) though the central space left vacant in both films, a large quantity
of the green rays (with red and yellow) through the yellow annular space which
intervenes between the central clear space and the red film, and a much larger
quantity of the comparatively inactive orange and red ravs through the outer or
red-cum-yellow portion of the compound screen.

page_text: By adjusting the proportions between the cential or clear portion, the outer
o red-cum-yellow portion, and the intervening yellow portions of the screen,
the quality of the light admitted may be regulated so as to obtain the most
porfect results
The screen is placed in the lens in the position usually occupied by the
Diaphragm on thereabouts
Improved Means applicable for use in Orthochromatic Photography.
I, RICHARD WILLIAM ARTLETT, of 38, Alexandra Road, Richmond, in the
County of Surrey, Photographer, 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 improved means applicable for use in photographing
pictures and other objects presenting a variety of colours, the actinic properties
of the different colouis presented by the object being modified to a greater o
less extent according to their well-known respective value in this respect With
the aid of my invention, not only are the various shades oi descriptions of colour
represented by appropriate half-tones, but from an artistic point of view a fai
more accurate result is obtained than by the means hither to commonly employed.
As is well known, the silver compounds used in the preparation of photographic
plates or films are extremely sensitive to the violet and ultra-violet rays, while
they are much less sensitive to the green and very much less so to the led rays,
although these two latter make up the most luminous portion of the spectrum
Visually
Plates specially prepared for orthochromatic photography have, by chemical
moans, been rendered more sensitive to the red and very much more sensitiva
to the green ays; but they are still so much less sensitive to those rays than
they are to the rays at the violet end of the spectrum that, to obtain a correct
rendering of an object comprising various colours, I cause the light from the
object to pass through a coloured screen which stops a due proportion of those
ays which act too energetically on the sensitive film
The accompanying diagrams illustrate the manner in which screens adapted for
accomplishing the objects aimed at are or may be constructed, Fig 1 being a
view depicting the yellow portion of the screen, Fig 2 a similar view depicting
the red portion and Fig 3 a view depicting the screen completed by uniting
the yellow and the red portions face to face. In preparing this improved screen,
I employ two discs of glass, Figs 1 and 2, which preferably have plane surfaces
but which may be ground to a slight curvature
Each of these 18 coated on one
side with a film of gelatine, collodion or other suitable material and each film is
then dyed, the one, Fig 1, a strong bright yellow, and the other, Fig 2, a clear
strong red
The yellow-dyed film permits the red, yellow and green rays to pass
and intercepts the whole or nearly the whole of the blue rays, whilst the ied-
dyed film operates to intercept the violet, indigo, blue and green lays In the
centre of the yellow film, there is a small circular vacant space a, and in the
centre of the ied film there is a comparatively large circulai vacant space b.

page_text: The two discs are now cemented together, film to film (Fig. 3), with Canada
balsain or other cement having a retractive power corresponding as nearly as
may be with that of the gelatine or collodion film
A coloured scicen prepared in the manner above described transmits a small
quantity of the very energetic blue and violet rays (along with the other 1ay's
constituting white light) through the cential space left vacant in both films, a
large quantity of the green rays (with red and yellow) through the yellow
annular space which intervenes between the central clear space a and the red
film; and a much larger quantity of the comparatively inactive orange and red
rays through the outer or red-cum-yellow portion of the compound screen
By adjusting the proportions between the central or clear portion, the outer
or red-cum-yellow portion, and the intervening yellow portions of the screen,
the quality of the light admitted may be regulated so as to obtain the most
perfect results, and although it is desirable to have a small cential vacant space
in the yellow-dyed film, it may, sometimes happen that the circumstances will
admit of the use of the film intact
The screen 18 placed in the lens in a position as near as may be to the
diaphragm
It will be obvious that the configuration of the screen may be varied according
to the conditions under which it is to be used
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I claim
-
1 For use in orthochromatic photography, the herein described means for
modifying the actinic effect of certain colour rays (such as violet, indigo, blue
and green) in proportion to others (such as yellow, orange and red) whereby a
correct rendering of a multiple-coloured object is obtainable
2. For use in orthochiomatic photography, a coloured screen prepared substan-
ially as herein described
tially as herein described
Dated this 22nd day of September 1899.
For the Applicant,
G. G. M. HARDINGHAM,
Chartered Patent Agent,
Clun House, Surrey Street, London, WC