The daily morning journal and courier. [volume] (New Haven, Conn.) 1894-1907, 1900-03-12
NEW COLOR PHOTOGRAPHY
PROFESSOR n. W. WOOD OF WIS
CONSTN
Lectures In London ora the Latest
Process.


versity recently lectured at the Society
of Arts on his researches in that fruit
full field of experiment color photo
graphy. Sir. w. De w. Abney occu-
pied the chair, and the audience in
Photographic experimentalists
Prof. Woods process is a simplifca-
tion of the indirect or "tri-color"
process, which owes it's existence to the
theories of Young and Helmholtz, and
the practice of experimenters, of whom
Clerk Maxwell; Ducos du Hanson,
and Frederick e. Ives are the chief. 1t
is a process for doing what the eye
does. We distinguish between every
color because our eyes have three sets
of nerves, each sensitive to one of the
colors, red, green, and blue. but STILL
in some degree, to the other two as
WELL White light is made up of rays
OF these three colors, and the coors of
every natural object are composed of
these three in some proportion. The eye
nerves separately sensitive to these
three colors combine them again in the
sensation which they give to the brain.
The Photographic method is an imita-
ton of the eyes method. Three mega
tives are made, through red, green,
and violet screens and from these three
transparencies are produced on glass.
Each of these positives represents the
amount of red, green, or violet in the
original colored object. If we view
them backed up with a suitable red,
green, or violet glass the actual
amounts of these colors will be seen.
To reproduce the object in its natural
colors it is only necessary to devise
means of viewing these three mono
chrome images at the same moment
Perfect mechanical contrivances, such
as Ives's "Kromskop,' exist, by which
this can be done, but they are compli-
Gated and delicate instruments. Prof.
Woods process is, in essential, a tri-
color process; but by an ingenious use
of a well-knoWn instrument the diff
fraction grating-it dispenseS at the
later stage with the three separate
images and the difficulties attending
their reconciliation.
A diffraction grating is a glass plate
ruled with very great number (2,000
and more) Of parallel lines. When
placed in the path of ray of white
light is spreads it out into spectrum
somewhat as does a prism, the chief
difference being that while the prism
gives only one spectrum, the grating |
gives double series of spectra, spread |
ing in opposite directions from a central
point The finer the ruling the more |
are these colored bands spread out. |
This Is the fact which lies at the bot |
tom of Prof. Woods process.
Taking a small frame containing a
lens, he places a grating behind it, and !
in the front of it, at a distance equal |
to the focal length Of the lens, an .
Opaque screen, so that an image of the
spectrum is cast on the screen. If a
hole be made in this screen at the spot
where the red portion of the spectrum
falls, the grating will appear red when
the eye is applied to this hole. If, on
the other hand, the aperture is made
where the green part of the spectrum
falls, the grating will appear green. If
now the grating be replaced by one of
such ruling as to project, the green part
of the spectrum over this first hole,
will produce the effect of white light
Tt is clear, then, that if we can obtain
Photographic transparency in which
the red, violet and green Of the original
are represented by gratings such as
have just been instanced, we shall see,
on looking through the aperture, a
view of the original in it's true colors, (
since these three colors will determine
all the others, and each diffraction
grating acts as though hhe others were ;
not there.
Suppose we wish to represent bou
quet of different colCTed blossoms; the ;
red flowers must have 1000 lines TO the S
inch the blue flowers 2,750, the yellow,
which we must make by mixture OF
red and green, double set of lines cor
responding to the red and green and
the white all three sets of lines. The
shadows and the darker colors must {
be represented by grating lines less dis
tinct, and in the dead blacks the lines {
are wholly absent. Complicated as
this arrangement appears, it can be t
accomplished quite easily, by the aid t
of photography; for the diffraction t
lines, once ruled on a glass plate, can {
be transferred to a sensitized film by 8
contact printing. a
Having made three transparent posi- I
tives through red, green, and blue i
Prof Wood proceeds to register G
these three images on a single plate, Q
a suitable grating in each
case his is done by throwing the t
image Of teh positive on to the screen c
by an arrangement similar to a magic n
lantern, and when obtained in sharp t
outline, pressing a sens1tized plate b
against the grating and exposing to
light. The positive is changed for an d
other, representing a different color a
the grating is likewise APP C
changed and second ex- t
posture given to the plate. In the same b
way third impression is made. The I t
result, when the plate is developed, is a
4 representa- ton of the original object t
So it is that when the plate is placed Il
before lens and viewed from certain c
point these three gratings give rise to I
he sensation upon the eye Of the OBJ W
server of every shade of color.
1t is the easiest thing imaginable to t
,opy a attraction photograph such as W
his. and in this fact lies the impor- "
ance and possibility of the process. e
At present it is difficult to secure SEN b
;itive plate fine enough in grain and at A
he same time rapid enough to be used N
n the camera but when this obstacle C
S surmounted-and it is not msur- d