[Illustration: THE COPYING AND DUPLICATING CAMERA.]
This apparatus, as will be seen in the engraving, is a camera with
an unusually long bed-rail and bellows. It has a central frame which
supports a lens, and a front frame supporting a negative, so placed
for duplicating or enlarging, which is done by transmitted light.
The front is fitted with a kit of frames for the various sizes of
negatives, from 3-1/4×4-1/4 to 8×10, or the largest size the box is
capable of producing.
For copying by reflected light the lens is removed from the central
frame and adjusted or attached to the front, where the negative is
seen in the cut; and the picture to be copied is attached to an
upright support (which is usually a part of the copying table or
stand) [p190] and exposed to the strongest diffused light
available, the camera being adjusted squarely in front of it.
For duplicating or enlarging negatives the adjustment of the
apparatus is as shown in the engraving. Such work being done by
transmitted light. The negative to be enlarged is placed in the
appropriate sized frame in front and the lens in the middle frame,
which is placed nearer to the negative than to the ground glass. The
conjugate focus is then found by drawing out the rear or ground
glass focussing screen until the image is sharply defined on the
glass. When the subject is sharply in focus, if the image is found
to be too small the frame supporting the lens is pushed a little
nearer the front; on the contrary, if the image is too large the
lens is drawn back from the front.
For all such work the camera should be directed toward a window
commanding a clear view of the sky, or if trees or buildings
intervene then a sheet of tissue paper or a square of ground glass
should be placed immediately in front of the camera and against the
window. It will be found that Anthony's "mineral paper" is superior
to either tissue paper or ground glass for this purpose, and should
be used when it can be procured.
When it is desired to make a duplicate negative it is necessary
first to produce a dia-positive or transparency; this is merely a
copy of the negative (by transmitted light, or light passing through
the negative to the lens) with its lights and shadows transposed or
reversed. Great care must be taken to have this transparency in
sharpest focus, and full-timed in exposure to secure line detail.
When a suitable positive has been secured it should [p191] be
dried and set up in the place occupied by the negative from which it
was made, and with the film side toward the lens.
The process is now repeated, but with a shorter exposure, and the
resulting picture is a negative (if well done) identical with the
original.
The adjustment for size is, as before mentioned, effected by moving
the lens support. If it is desired to enlarge, the lens is moved
nearer the subject; if to reduce, move the lens back from the front.
If the duplicate negative is to be of the same size as the original,
the lens is moved to the position near the centre between the front
and back, which will give the image on the ground glass the same
dimensions by measurements as the original.
It will be observed that as there are two plates to be used the
utmost care must be taken in the adjustment of the focus and in
timing the exposure in both instances, to avoid loss of definition
or quality.
Duplicates and enlargements of negatives made by this process and
with dry plates need be in no particular inferior to the originals,
if care and skill are exercised in their production.