When a negative happens to be of larger size than a quarter plate, it
rarely happens that we can print a small portion by contact on a
lantern plate without spoiling the composition of the picture. This is
assuming, of course, that the operator has composed a picture and not
put his camera down anywhere. There is no great difficulty in making
lantern slides by reduction; the exposure is the only bugbear, as
usual.
There are two distinct methods of reduction: (1) daylight; (2)
artificial light. There is nothing to choose between them, and the
question of time and opportunity must decide which is to be adopted.
The apparatus required is not expensive. It can be made in odd moments
for a few pence, and is applicable to day and artificial light. It
consists of a printing frame the size of the large negative, four
pieces of bamboo a quarter of an inch in diameter, some black twill,
the ordinary camera and lens, and a carrier to take lantern plates 3¼
X 3¼ inches.
The negative is placed in the printing frame upside down and kept in
position by four little slips of wood, or better still, a frame such
as the gold slip used in picture frames, which will fit tightly into
the frame and hold the negative securely. Of course, brads may be
driven into two sides of the frame and the negative slipped behind
them, but in this case it is necessary to safe edge the negative. This
is done by cutting strips of tinfoil just wide enough to cover the
rabbet of the negative so that no clear glass can be seen; these
should be pasted and stuck on the glass of negative round the four
sides. The strips of bamboo are either nailed to the printing frame or
merely fastened together by stout copper wire, the shape being exactly
that of the printing frame. The other end of the bamboos are tied with
stout string to a piece of cardboard tube, postal tube, which slips
over the lens. The length of the bamboos depends upon the focus of the
lens and the amount of reduction. It will sometimes be found
convenient to have the bamboo in two lengths; thus, supposing we want
as a general rule 36 inches, two pieces, 24 inches each, should be
obtained, and by fastening these together in the middle by two loose
rings of copper wire we can extend them to 48 inches or reduce them to
24 inches.
The black twill or the focusing cloth (or even a dark table cloth may
be used) must also depend for its size on the length of bamboo, but
sufficient should be obtained to completely cover over the space
between lens and negative, and hang down on each side.
Of course, two laths of wood can be used, merely resting them on the
top of printing frame and camera, but the other plan is preferable,
the arrangement being more complete and adaptable to both day and
artificial light, and also more rigid, especially when the camera is
sloped toward the sky.
The ordinary camera may be used, but a carrier to take lantern plates
must be used in the dark slide. The ordinary lens may be used unless
of inordinately long focus, when it becomes inconvenient on account of
the great distance between negative and lens. To find the required
distance there is a simple rule, which is as follows:
(a) Divide the longer base of the plate by the longer base of the
image required, to the quotient add 1, and multiply by the focus of
lens used; the result will be the distance between negative and lens.
(b) Divide the distance found as above by the quotient obtained in the
first rule, and the result will be the distance between lens and
plate.
Example.--What are the relative distances in reducing a whole plate
negative, 8½ X 6½ inches, to lantern, size with an 8 inch focus lens?
Now that the whole of the lantern plate is not used, we reckon that 3
inches is all that can be used, because of the mask, hence:
(a) 8½ ÷ 3 = 17/6 = the amount of reduction.
17/6 + 1 × 8 = 23/6 × 8 = 30-2/3 inches.
(b) 30-2/3 ÷ 17/6 = 11 inches (practically).
Therefore, if we place our lens about 30 inches from the negative and
rack the camera out to about 11 inches, we shall have an image on the
ground glass which merely requires a little adjustment of the camera
screw to be sharp and of the right size. In focusing, it is always
advisable to temporarily affix to the outside of the focusing screen a
square mark, this being, of course, accurately placed as regards the
center of the screen, and to use a focusing magnifier to obtain
critical sharpness.
Having satisfactorily arranged our image as regards composition by
shifting the camera nearer to or farther from the negative--because it
will be obvious that the nearer the lens to the negative, the less of
the negative we shall include, and vice versa--we fill our dark slide
and are ready for exposure.
For daylight work the arrangement of frame and camera should be placed
near a window, and if anything but sky is seen opposite the negative,
place outside the window a large sheet of white cardboard at an angle
of 45°. This will reflect equal skylight through all parts of the
negative. Now cover over the space between negative and lens, insert
your dark slide, in front of the negative place an opaque card, draw
the shutter of the dark slide, and remove the opaque card from
negative and expose.
Very little assistance can really be given as to exposure, but with a
negative of average density, which will give a good silver print, and
using a lens working at F/11 and a Mawson lantern plate at midday in
May, ten seconds will give a good black slide.
There is but one little point that has been missed--the diaphragm;
always use the largest diaphragm which will give satisfactory
definition, this will usually be F/11 or F/16.
Be very careful while exposing not to shake the camera--it is quite
sufficient for anyone weighing about eleven or twelve stones to walk
across the room to give double outlines.
Daylight is not a constant quantity, and although visually the same on
two different days, the actinic power of the light varies enormously;
therefore we prefer artificial light.
Precisely the same apparatus can be used for artificial light with one
or two additions. In some such arrangement in use the printing frame
containing the negative is fastened to the side of a cube sugar box in
which a hole is cut.
Opposite to the negative on the other side of the box is placed a
sheet of white cardboard bent slightly to the arc of a circle. The
lights, etc.--two incandescent gas burners do well with tin reflectors
behind them--are placed one on each side of the negative inside the
box, so that the light is reflected on to the card and thence on to
the negative, and no direct light reaches the negative. Absolutely
even illumination, even of a large negative, is thus obtained, and the
exposure, using the same conditions as stated for daylight, is only
twenty seconds.
Of course, the light may be placed directly behind the negative, but
in this case a diffuser, such as a sheet of opal glass, must be placed
between light and negative, and even then, unless great care is
exercised, uneven illumination of the negative and consequent unequal
density of the slide must ensue.
We may use magnesium ribbon, and a diffuser of opal is then necessary,
and the ribbon must be kept in motion the whole of the time. Magnesium
is objectionable because the particles of magnesia form a voluminous
cloud, which tastes and smells unpleasantly and settles down on
everything. Still, for those who wish to work with this substance,
about 18 inches burnt close to the opal and moved about all over it
will be about sufficient to obtain good results under above mentioned
conditions. An ordinary oil lamp or gas may also be used, provided the
light is diffused.
Only the bromide lantern plates are suitable for reduction, the
exposure, especially with the chloride emulsions, being so long as to
place them out of court. The chloro-bromide may be used for daylight
and magnesium ribbon.
After development and fixing, which may be performed in the developers
recommended by the makers of the plates used, the lantern slide must
be well washed and cleared in an alum and acid bath, then again well
washed and finally given a gentle rub with a piece of cotton wool
under the tap, and set up to dry.
The finishing off of a slide is not a difficult matter, but one which
wants doing properly. Place the slide film downward upon a piece of
white paper, and with a box of assorted masks try various shapes till
the one most suitable to the picture is found, and frequently a mask
with a comparatively small opening will give the best results
pictorially. Having found the most suitable mask, lay it on the slide,
on the top of this a cover glass well cleaned, and it is ready for
binding. Binding strips can be purchased commercially in long strips,
but personally we prefer to use 3¼ strips, as somewhat easier to
apply. Wet 3¼ in. of the strip, lay it flat on the table, pick up the
slide and cover glass and adjust on the wetted slip so that there is
an equal width on either side; now press the glasses firmly on to the
strip and lift from the table and with a handkerchief or soft duster
wipe the strip on to the glass of the slide and cover, taking care
that these do not slip; when it adheres firmly, that is, does not
immediately rise up, lay the whole on one side and go on with next
slide; by the time half a dozen have been thus treated a second side
may be stuck down, and thus with the third and fourth. By working in
this way a far neater and safer job is made of it than if all four
sides are bound at once.
The final operation is tilting and spotting. There are several makes
of masks on the market on which a blank white space is left for the
title, and it is just as well to write the title on the mask, as it is
then protected by the cover glass. If the ordinary masks are used,
Chinese white may be used for the titles.
"Spotting" the slides is affixing to them two marks, by means of which
the lantern operator can tell which side is to be placed next the
lantern, and these marks usually take the form of two white circles.
Such "spots" can be bought commercially already gummed, or postage
stamp edging may be used.
A few minutes' thought will show that the projecting lens of the
lantern will reverse an image just as the lens of the camera does, so
that we must insert the slide into the lantern carrier upside down and
wrong way round, and as the spots are used to indicate this, they must
be placed at the top of the slide, when the view appears to us as we
saw it in nature. If it be a subject with lettering in it, the spots
must be placed at the top of the slide, when we can read the lettering
the right way as the slide is looked at against a piece of white
paper.
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