[Illustration: FIG. 106.--MOUNTINGS FOR TRIPLICATORS.]
While doubles are well known to many amateurs, the making of three
exposures of one subject on a single plate is not so common. Mr. Chas.
A. Barnard has furnished particulars of his method of making the
pictures shown in Figs. 107 and 108. Fig. 106 shows two methods of
mounting the attachment in front of the camera lens, one being
designed to slip over, while the other screws into the lens barrel,
the front of which is often fitted with a screw thread. Fig. 109
shows the stops which slide in this mounting; in making them, first
mark on each the position of the center of the lens by measuring up
from the stud which holds the stop in place. Draw your circles for
stops with this as a centre, and as large as diameter of lens. Leaf A
is used for the sides of the triplicator, reversing between the
exposures. With an inch circle, the width of this is 0.2 inch. The
edges should be filed down as thin as possible without nicking. Leaf B
is for the centre exposure of the triplicator, and the slot is 0.012
inch wide and 1 inch long. Leaf C is the duplicator stop, its width
being 0.3 inch. Leaves D1 and D2 are for top and bottom exposures of a
vertical double, and are the same size as C. The proportions might
have to be slightly varied for some other lens, in all these cases. A
triplicate exposure is made as follows. First focus, using the whole
lens, at any stop, and determine the limits of your picture spaces. As
the leeway is small, do not get the figures too large. Pose the model
in the centre, stop down till properly lighted, and note the stop and
mark edges of view on ground glass. Focus on model at one side, stop
down till edge blends into edge of previous view, and note stop. Do
the same in third position. This may take some time, and a chair may
be used instead of a model. Finally, put in the plate and make the
three exposures, giving four times the exposures ordinarily required
for the same stops. The order is immaterial. Stops recommended for a
3-1/4 x 5-1/2 camera are as follows: For a horizontal doublet, leaf C,
U. S. 16; for a vertical doublet, leaf D1, U. S. 54, leaf D2, U. S.
40; for a horizontal triplet, leaf A, U. S. 16, leaf B, U. S. 90; for
a vertical triplet (leaves not shown in drawing), leaf A for top, U.
S. 32; for bottom, U. S. 20, leaf B, U. S. 90. Vertical pictures are
extremely difficult to figure.
[Illustration: FIG. 107.--TRIPLICATE EXPOSURE. BY CHARLES A. BARNARD.]
[Illustration: FIG. 108.--FARM WORK (TRIPLICATE EXPOSURE). BY CHARLES
A. BARNARD.]
[Illustration: FIG. 109.--STOPS FOR DUPLICATORS AND TRIPLICATOR.]