The times. [volume] (Washington [D.C.]) 1897-1901, 1900-07-22
these few with great expenditure of time

| these few with great expenditure Of time
work, and money.
| The success of this method depended
upon the same principle that explained the
| reproduction Of color in muriate OF silver
| the Interference of light waves, through
reflection. Lippman put a transparent,
| highly sensitized film in immediate contact
with a mirror backed with mercury. Light
passing through the film was reflected back
along the same line by the mirror. Ad-
yancing light waves and reflected light
waves, meeting under certain conditions,
cancel or neutralize one another. the re-
suit being white light minus these can
celed waves-that Is. colored light.
Color waves differ in wave length &C
cording to the different lines OF the spec
trum, SO the conditions under which the
direct and reflected waves meet vary &C
cording to their color. and the films re-
cord this variance. The white light en-
tering the camera has been separated into
its component parts-pure white light be-
ing composed of all the hues of the spec
trum-and when the film is again exposed
to white light it shows the impression re-
ceived in colors. One great disadvantage
OF these Lippman photographs is that the
white light must fall upon the completed
film at a certain angle in order to give the
color effect. Seen at any other angle. the
dpuS lOOh line C0l0tte55 NEGATIVES.
Success by Indirect Methods.
The only practical success in color pho
Biography SO far has been accomplished by
indirect methods; and. though these pro-
cesses may not be so interesting from the
viewpoint OF abstract science as the Lipp-
man process. their commercial value is in
-finitely greater. Indirect color phutogra-
ply primarily consists in the production
of three separate negatives, taken through
screens of the three primary colors, red,
green, and blue, and in the optical super
position of these images; but there have
been innumerable developments of this
process. The original composite color pho
Biography, requiring three separate mega
tives obtained by three separate exposures
and three separate positives projected by
a single lantern, was too cumbersome and
complicated to be practicable.
A great effort has been made to bring
the process into such shape that 1t could
be easily accomplished even by the anna
teur and the apparatus required for it car
ried as easily as the ordinary camera. No
such conditions have been attained, but a
good deal has been accomplished, and the
pEotochromoscope, with its more recent
the kromskop, Is thought by
scientists to come as near a solution Of
the problem as any Of the later inventions.
BY this photochromoscope process the
three negatives are taken upon single
sensitive plate at one exposure, and the
contact positive, cut into three sections
with scissors and mounted upon q folding
cardboard, is dropped into the photo
which, as well as the camera,
may be made stereoscopic, the size of the
ordinary hand stereoscope. The camera
Eliminates three colorfess transparent
positives separately by lights Of the three
primary tints, and these Impressions are
OFFICIALLY recombined into one colored
image in the seeing apparatus or photo
OF course, this seeing in