I place the tank in front of
the lens, in contact with the lens-mount. The advantage of this tank and
solution is that it can be more easily obtained than yellow plate glass,
and the color can be adjusted to meet any requirement.
The plates require about three times as much exposure through the yellow
screen as without it, and may be developed with the ordinary alkaline
pyro-developer.
[Illustration: IVES' PROCESS OF ISOCHROMATIC PHOTOGRAPHY.]
In order to illustrate the value of this process, I made two photographs
of a highly-colored chromo-lithograph, representing a lady with a bright
scarlet hat and purple feather, a yellow-brown cape and a dark-blue
dress. One, by the ordinary process, represents the blue as lighter than
the yellow-brown, the bright scarlet hat as black, and the purple feather
as nearly white. The other, by the chlorophyl process, reproduces all
colors in nearly the true proportion of their brightness, but with a
slight exaggeration of contrast produced purposely by using a too-strong
color solution in the small tank.
I also made two landscape photographs, one by the ordinary process, and
the other by the chlorophyl process, exposing them simultaneously.
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