Transparencies for the decoration of windows, or gas shades, or for
examination in the stereoscope, differ from those intended for
lantern projection in being somewhat more intense. A lantern
transparency must have its high lights of pure glass; in the case of
the others, it is of less consequence, should they be slightly
shaded.
To produce a transparency by wet collodion, a camera is required the
body of which will be capable of extending to twice the focus of the
lens, although a still further extension is desirable. The reason
for this lies in the fact that when making a transparency the same
size as the negative, the sensitive plate must be withdrawn from the
lens to the extent of precisely twice the solar focus. It
occasionally happens that it is desirable to make the image in the
transparency on a scale a little larger than that in the negative.
To permit of this being done, it is necessary that the distance
between the sensitive plate and the lens be increased, for according
to this distance, so is the amount of enlarging.
The negative must be so arranged as to have a clear sky or a uniform
light behind it. If the work is to be effected at a south window
into which the sun is shining, the requisite uniformity of
illumination is obtained by placing a sheet of ground glass within a
few inches of the negative. Arrangements must be made by [p219]
which the negative may not only be held rigidly in an upright
position, but that such adjustments may also be made as will bring
it as near to or as far from the lens as will be found requisite,
and also as will permit of its being raised, lowered or having any
part far removed from the centre brought into the axis of the lens.
These conditions are fulfilled in all good transparency cameras. We
do not assert that a properly constructed camera for the special
purpose of making transparencies is an absolute necessity, seeing
that a light framework erected in front of the camera, and with
which it need not be connected with a bellows body, will suffice,
but the great convenience of a camera expressly for the purpose
cannot be overrated.
In order to ensure clearness of the high lights, the collodion
should be rendered of a dark sherry color by the addition of a few
drops of an alcoholic solution of iodine. The strength of the
solution is not of consequence, but enough must be added to the
collodion to render it of the color indicated. Collodion for this
purpose works rather better after it has been kept for a few weeks
or months than when it is quite new. No hints can here be given as
to the length of exposure requisite, but if the camera be pointed to
a moderately bright sky, the negative one of average density, and
the lens worked with a small diaphragm, an exposure of twenty-five
or thirty seconds may be given, and, by noting carefully the quality
of the resulting picture when finished, the data for a more accurate
timing of the exposure may be ascertained therefrom.
After developing the image with iron, if it should, upon examination
prove to be too thin, wash off the developer and apply pyrogallic
acid and silver and bring it up to the required intensity. Fix and
wash. [p220]
At this stage--that is, after fixing and previous to the plate being
dried--the image may be toned to almost any desired color. It is to
be regretted that some of the most desirable tones cannot be
recommended, on account of the want of permanence. A type of the
best of this class of toning agents is as follows: Make a saturated
solution of bi-chloride of mercury in hydrochloric acid and dilute
it with twelve volumes of water. Into this place the plate, after
having thoroughly removed the hyposulphite by washing. When it has
become quite bleached, wash carefully again and place in a bath
composed of a dram of sulphide of ammonium to a pint of water.
The image will soon acquire a rich dark brown color, and when this
is found to have penetrated the film, it may be washed, dried and
varnished.
A solution of sulphide of potassium imparts a good brown color.
Chloride of gold gives a tone which may be described as a neutral
black, that is both durable and very pleasing for quite a variety of
subjects.
A solution of chloride of platinum gives a tone which is very
permanent. It is essential when using either gold or platinum that
the toning solution be weak.
It is possible, however, so to develop a collodion transparency as
to obtain a rich purple black tone without any after toning. The
addition of a few drops of a saturated solution of citric acid per
ounce of developer effects this, but as it checks development at the
same time, the proportion of protosulphate of iron must be increased
to such an extent as to impart energy to the developer. [p221]
A few drops of a solution of gelatine in sulphuric acid is also of
great utility when added to an iron developer. It promotes clearness
of image and richness of tone.
[Illustration: ANTHONY'S BICYCLE CAMERA.] [p222]
How delightful a pleasure it is in the early morning, or of a fine
afternoon, to mount a bicycle and take a spin along the country
roads.
The bracing air, the easy motion, the sense of independence, so act
upon the mind as to make it keenly sensitive to the beauties of the
foliage and scenery that so swiftly pass before the eyes. Such must
have been the thought of him who penned the following:
"Most of us, no doubt, have experienced the desire, as our machines
have passed some pretty and specially picturesque bits of scenery,
to take away with us some memory, to be recalled at some future
time, of what we were then passing by. And most of us have also
experienced the difficulty, as one picturesque scene is replaced by
another, and so on to the end of our journey, of preventing the many
scenes getting somewhat blended in our minds, and an inability to
produce details with accuracy. To sit and sketch such scenes would
be to reduce the journey to a sketching tour, and the distance to be
covered must be reduced accordingly, thus depriving the 'cyclist' of
the usefulness of his machine.
"That which this tourist desires may be accomplished by the aid of
photography, and the whole addition to the impedimenta of the
'cyclist' can be so arranged as to be trifling.
* * * * *
"The apparatus consists of a tripod, camera and case. My camera,
with leather case and provisions for exposing a dozen 5×4 plates,
weighs between fourteen and fifteen pounds.
* * * * *
"I have endeavored to show in the brief space of time [p223] at
my disposal, how the enjoyment of a 'cyclist's' ramble may be
enhanced by that most wonderful combination of chemistry, optics and
mechanics, which has resulted in placing the science of photography
within the reach of the amateur.
"When we have imprisoned our sun pictures, and have them safe,
though latent and invisible, intangible and impalpable to any of our
senses, we may at our leisure (it may be months after), by means of
those marvelous chemical affinities which throw the haloid salts of
silver again into chemical life, produce on the film the pictures we
have so desired; and then again, by further use of the light, we
print our scenes on the sensitive paper. We have then a pictorial
history of our journey in our albums, which will recall the pleasant
memories of happy days spent long, long years ago.
"FRANK COBB."
The amateur who wrote as above rode on a tricycle and carried a load
of apparatus for 4×5 plates, amounting to fourteen or fifteen
pounds, for a dozen pictures. That is the way it is done in England;
but in this country mechanical skill has reduced that load to less
than five pounds for two dozen pictures of the same size, and the
cyclist goes forth with a small camera and a roll-holder charged
with films for 24 exposures, which are carried in a small case
supported by a strap passing over the shoulder, and these films are
so sensitive that it is not necessary that he should dismount and
undergo the trouble of erecting a tripod, and attaching his camera
thereto. He has only to fix his camera by a universal joint to his
steering-bar and shoot as he flies, with the full confidence that at
the proper time [p224] he will find his bit of scenery spring
into beauty and brilliancy under the influence of the developing
solution. Or if the exigencies of the situation require that the
point of view would be better off the road, then the wheel is very
easily converted into a support for the camera by the little brass
telescopic rod which is adjusted against the pedal at the side of
the wheel by a strap, and lengthened to reach the ground, against
which the wheel may rest quite sufficiently steady for all purposes
in question.
The little camera, with double holder telescopic support for wheel
and the case, will weigh about two pounds, which may be carried by
means of a strap on the shoulder, or may be buckled to the saddle of
the machine.
The detective camera, also, is quite well suited for such a purpose,
with the roll-holders or otherwise, as may be desired; but the paper
films are more sensitive than the plate, and are, therefore, more
suitable for such rapid work as may be required.