VIGNETTING
Of the many varieties of small portraiture, the vignette is, perhaps,
the most popular, and, when well done, is certainly the most refined
and delicate. Two things are to be especially avoided in vignetting.
The form of the vignette should not follow the form of the figure
closely, as it is too often made to do, and dark backgrounds should
not be employed. The qualities to endeavour to attain are softness of
gradation, and an arrangement of the forms of the vignette that shall
throw out the head and figure, and the resulting print should somewhat
resemble a sketch, finished if you like, but sketchy in effect. Although
the background should be light, it ought not to be white, but of a
tint that would just throw up the white of a lady's head-dress. If the
background screen could be painted so that a little shade should appear
over the shoulders of a sitter for a head, or rather darker behind the
lower part of a three-quarter figure, so much the better would be the
effect. It would be difficult to find a case where gradation could not
be of advantage in a background; however slight, it conduces especially
to relief.
Having stated what should be aimed at in vignettes, we now come to the
technical methods of producing them.
In many cases vignetting is considered to be a merely mechanical
operation, and very often looks like it. Perhaps the trade have more to
answer for than the printer, since the qualities of the wares advertised
for the use of the vignetter are often exaggerated to such a degree that
they are supposed to be suitable to any pictures. Vignette glasses are
not so common as they used to be, but they certainly are useful in some
instances; we almost think that the methods of producing vignetting
apparatus which will be described shortly, superior to them. In case the
printer should wish, however, to use these glasses, here is a method by
which he may produce them. Have a piece of orange glass, flashed on one
side only, rather larger than the size of the picture to be vignetted.
Take a rough print, and trace round, in the proper position on the
glass with an ink line, the point to which the picture should extend.
This should be marked on the unflashed surface of the glass--that is,
the surface on which the glass is uncoloured. Place the plate so marked
on a white surface, flashed side uppermost, and make a solution of
hydrofluoric acid and water, 1 part of the former to 3 of the latter,
in a gutta-percha dish or bottle.[22] Make a pad of flannel and cotton
wool at the end of a stick, about the size of a large nut, and drop
this into the solution. Dab this on the coloured surface of the glass
in the central portions where the print is to be completely printed in,
gradually working out to the inked line. Always work from the centre to
the edges, and dilute the acid with a little water as it approaches the
margins. By degrees the flashing will be dissolved away in the centre,
and, if properly performed, the colour will gradually be eaten away,
till the glass is colourless in the centre, and keeping its full shade
of orange at the ink lines. The glass is then washed, and is ready for
use.
The most popular plan of vignetting is with cotton-wool. We believe that
the greater part of the vignetting done in England is by this clumsy,
costly, and difficult method. It requires more time and attention than
any other way of producing the same results. Its advantages are, that it
is more "elastic," and allows the operator more scope for attention than
other methods. In the hands of a person who has very great skill, taste,
and patience, it is undoubtedly most useful; but when used by anything
lower than the highest skill, the results are almost always hard and
inartistic. The operation is thus performed. A hole is cut in a piece
of cardboard, which is placed over the negative. Under the edges of the
cardboard is placed cotton-wool, which is lightly pulled out, so as to
slightly shade the vignette, and produce the vignetting gradation.
The next methods of vignetting are dependent on simple laws of optics.
Suppose you cut a round hole in a card, say, half-inch in diameter, and
so arrange it that all the light getting to a sensitive paper comes
through this hole, and that the card is for our experiment placed
half-an-inch from the paper. Now place the hole so as to face the sky,
but so as the sun has no direct rays falling through the hole. It will
be found that the greatest darkening will not occupy a space exactly
opposite the hole, but be _away from the side on which the light is
brightest_. The dark round patch will be shaded gradually off till
a line is reached where, practically, the light has no effect--that
is, if the surface of the card next the paper be blackened. It will
be noted, however, that the shading is not equal on both sides, but
that the gradation is most extended away from the side on which the
light is brightest. A good example of what is meant will be to try the
experiment of placing the paper and card flat on the ground in the
angle between two walls, both of which are in shadow. It will be seen
that the brightest gradation takes place in the direction exactly away
from the angle of the walls. Next repeat the experiment, making the
hole point to the sky, which is equally illuminated and pointing well
away from the sun. It will be found that the gradations are equal, and
the greatest darkening exactly opposite the hole. Raise the card next
to the height of one inch, and the gradations will be found to be more
extended and softer. The reason of this can be well understood by a
glance at the figures. In both, suppose A B to represent the section of
the card, and C D the hole in it, and the dotted circle the sky, and E
F the paper. Take the points _a_, _b_, and _c_ on the paper, and let us
in the three instances see what relative illumination they will receive.
_a_ is opposite the hole, and receives the light from a circle of sky of
which _d e_ is diameter, and _b_ from an ellipse of which _h k_ is one
diameter, and _e_ from an ellipse of which _f g_ is one diameter. In the
first case, where the card is 1/2 inch from the paper, _h k_ is about
one-fifth of _d e_, and _g f_ about one-third of _d f_, and since the
ellipses vary as their two diameters multiplied together, the point _b_
would receive only one-twenty-fifth the light that _a_ received, and _c_
about one-ninth.
[Illustration: _Fig._ 21.]
[Illustration: _Fig._ 22.]
In fig. 21 the card is raised one inch from the paper, and here _f g_ is
about three-quarters of _d e_, and _h k_ about two-fifths; therefore,
in this case, the light on B would be only four-twenty-fifths, or about
one-sixth of that acting on _a_, and about nine-sixteenths or one-half
nearly on _c_. It is thus evident that the further away the card is,
the more extended will be the gradations. Again, suppose, in the last
figure, the bit of sky at _g f_ was twice as bright as at _d e_, then
the amount of light acting on _c_ would be the same as that acting on
_a_. It will thus be seen how important it is for proper gradation that
the hole in the card should be exposed to an equally illuminated sky,
or that some artifice should be employed to render the illumination
equal. If we paste a bit of tissue paper over C D, this is accomplished,
for then it becomes the source of illumination, and it is illuminated
equally all over, since on every part it receives the light of the whole
sky; but this is not the case if it is transparent to diffused light,
and is never the case if it is exposed to direct sunlight, since a
shadow of the hole is always cast on the paper beneath. If you choose to
put another piece of tissue paper, (say) one inch above the hole, and
extending over the whole length of the card, this difficulty is got rid
of, and this last piece of tissue paper illuminates that pasted over the
hole C D, and the gradations will then be nearly perfect.
Now to apply the above to forming a vignetting block.
Suppose we have a one-inch head to vignette and to show the shoulders
and chest, to be of the size of a carte-de-visite, that the background
is about a half-tone between black and white, and that but a trace of
it shall appear above the head. To make a good vignette, the graduation
from black to perfect white should lie within a limit of half an inch
for a carte size portrait. The question then arises at what distance
from the plate should a vignetting card be cut to help this object,
and what shape should be made the hole in the card. We take it that
one-fifth of the light necessary to produce a full black tone would
hardly produce any effect on the sensitised paper; knowing this and the
size of the aperture, we can calculate exactly what height the card
could be raised. Take the breadth between the shoulders that is to be
fully printed as 1-1/2 inches, then by constructing a figure similar
to figures 18 or 19 we shall find that the necessary height is about
one-third of an inch.[23]
[Illustration: _Fig._ 23.]
By judiciously cutting out an aperture in the card and vignetting,
defects in a background may often be entirely eliminated from the
print. Proceed in this way: Take a print of the portrait, and cut out
the figure in such a way as to get rid of the defective background,
and then place this on a piece of thick card (we prefer a thick card,
since it will not sag easily, and thus alter the gradation), and cut out
an aperture corresponding to it. The outsides of most carte-de-visite
frames are raised from the glass about one-third of an inch; place the
card on the front so that the aperture corresponds to the figure on the
negative, and tack it on to the frame. The dotted lines (fig. 23) show
the card fastened on to the frame, and the opening left. This latter
may be covered with tissue paper, and the frame placed in diffused light
from the sky. In some cases it may be necessary to use a larger printing
frame than the ordinary carte frame, in which case the operator should
be able to make a vignetting apparatus raised at a proper height from
the glass. Suppose it is required to raise the opening half an inch
above the glass, and that the card is 4-1/4 by 3-1/2.
[Illustration: _Fig._ 24.]
Take the card and rule rectangles as shown (fig. 24), the inner one
being 4-1/4 by 3-1/2 inches, the next one 1/2 an inch outside that,
and the third 1/2 an inch outside that again. Cut out the outer
rectangle entirely, so that we have a piece of card of the size ABCD.
Take a needle point, and prick through the card at the points EFGH and
join these points at the back of the card by lines. Now take a sharp
penknife, and, having laid a flat edge along, cut the card half through
its thickness along KL, LM, MN, and NK. Turn the card over, and cut
along the lines corresponding to EH, HG, GE, and FE, also half way
through the thickness of the card. Turn the card over once more, and
cut out the shaded pieces at the corners. Now bend the card along the
cuts, and a raised block will result of this shape. The corners are
held together by pieces of gummed or albumenized paper, and the block
is ready for an aperture to be cut in it according to the portrait to
be printed. Wooden grooves may be glued along the top of the vignetting
frame, into which cards containing other apertures can be slipped.[24]
[Illustration: _Fig._ 25.]
The most practical method of vignetting, a modification of the above,
and the one we always prefer in our own practice, is as follows:--
[Illustration: _Fig._ 26.]
Take a piece of soft wood, half an inch thick for a cabinet size--a
thinner piece should be selected for a smaller picture--of a larger
dimension than the negative; in the centre of this cut a hole of the
shape of, but much smaller than, the desired vignette. One side of the
hole should be very much bevelled away, as represented in this section
(fig. 26). Place this block on the glass of the printing-frame, bevelled
side under, the hole being exactly over the part of the negative from
which the vignette is to be printed. The hole must now be covered with
tissue paper or ground glass, and the frame placed flat on a table to
print. The size of the hole in relation to the size of the vignette
will be easily ascertained by a little experience without the labour of
elaborate calculations. On dull days the tissue paper or ground glass
may be omitted.
This method is very simple and effective. A quantity of vignetting
blocks of various sizes and shapes could be made by a carpenter, or by
the printer, and should be always at hand.
A vignetting block should never be less than a quarter of an inch away
from the glass, otherwise the gradations will be too abrupt.