Camera Work: A Photographic Quarterly (1903 (Heft 2))

when superposed shall give the colored result for which we have been
working. The blue transparency in this process takes the form of an
ordinary "black-tone lantern-slide ” toned to a greenish-blue color with
iron. The other two negatives are printed upon celluloid coated with a
silver emulsion in gelatine, which have been treated with bichromate before
use. The silver salt gives a visible image and prevents the spreading of
the light-action. The bichromated gelatine is what is really used and the
" carbon print ” is developed in warm water in the usual way. The only
variation is in the exposure. The celluloid being very thin, exposure is
made through it so that development can be carried on without transfer.
The " carbon prints ” so obtained are placed in hypo to extract the silver
salt no longer wanted, washed and stained in solutions which are prepared
for the purpose by Mr. Sanger Shepherd, the constitution of which has not
been published. Of superposition little need be said, except that it is not
difficult and that the films may or may not be cemented together by means
of balsam at the taste and fancy of the photographer. This in outline is
the Sanger Shepherd process.
MESSRS.A.& L.Lumière, of Lyons, have also worked out a process of
three-color photography of a closely similar character. The main point of
difference between it and the foregoing is to be found in the fact that
Lumière plates instead of Cadett are recommended and the exact composition
of the dye-baths and light-filters is published. The prints are made upon
specially prepared bichromated gelatine on a paper support and are
transferred before development. A modification of this is known as the
L. N. A. process, the initials standing for the Lumière North American Co.,
Ltd. The principal difference lies in the substitution of thin mica for the
celluloid or paper as the support of the bichromated tissue, which is of
considerable advantage when the lantern-slide is made, as it is less likely to
be affected by the heat of the lantern than any other vehicle.
NOTHING has been said hitherto about the variations of the three-color
process as applied to what is known as " half-tone” work. On this subject
there is little to be said from the standpoint of the ordinary photographer,
since the operations lie altogether outside the possibilities of his work.
The process is the most hopeful of any as far as prints on paper are
concerned, yet it must be admitted that at present it leaves very much to
be desired, suffering from the defects of all three-color work.
WHAT are those defects? we hear some one ask. Exactly where they
lie is difficult to determine, yet their effect is easily seen. It is doubtless
due to some shortcoming of the method that we never see delicate,
" impure ” colors successfully reproduced, at any rate by themselves. It
seems that there must be some strong, garish tint in the picture to which the
photographer can work and by which he can guide himself, or rather the
process, and stain or wash out or otherwise modify the pigmenting until the
result seems reasonably correct.
ENTHUSIASTIC three-color workers will protest, no doubt, that this is
not so; but the facts must be left to speak for themselves. The colors or

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