Among the examples we have received are some which would certainly do
credit to any professional artist, alike for the posing, lighting, and
general treatment; indeed, we may say that some of the poses are of a
high artistic order, and quite a relief from the conventional positions
and accessories so frequently seen in professional work. The expressions
secured are also, as a rule, unusually pleasing and natural. This is, no
doubt, in a great measure due to the sitter feeling more at ease in the
amateur friend's drawing room than in a stranger's studio. Particularly
is this the case in some excellent work--full-length pictures--sent
from the other side of the Atlantic, and taken in a room of very modest
dimensions, and with only one window. Among the failures (if such they
may be called) the chief fault lies in the lighting, and from either
under or over exposure--the former chiefly arising when a landscape lens
was used, and the latter when a portrait combination was employed. Some
correspondents also complain of the long exposure that, in their case,
had been imperative; but, curiously enough, with all the successful
pictures a very brief exposure has always been mentioned, and generally
with an exceedingly small window.
With a view to the further assistance of those who have met with
difficulties, we recur again to the subject of the lighting, for
upon this must entirely depend the success or failure in producing
satisfactory results; and, as we explained in previous articles, unless
proper _chiaroscuro_ is secured on the model, it will be impossible to
obtain it in the picture. The chief defect in this respect has been
either that the light has been too abrupt, and consequently the high
lights are very white and the shadows heavy, giving the pictures an
under-exposed appearance, or the face is devoid of shadow, one side
being as light as the other; hence it lacks the roundness necessary
to constitute a good picture. In most instances the former defect has
arisen from the reflecting screen not being properly placed so as to
reflect back the light in the right direction, or it has been too far
from the model; hence it has lost the greater part of its value. It
should be borne in mind that the nearer the sitter is to the source of
light the nearer the reflector must be to him, and also that at whatever
angle the light falls upon the reflector it is always thrown off at a
corresponding one.
Now, supposing that the light falls upon the model at an angle of, say,
40°: we shall have to place our reflecting screen at somewhat the same
angle, and the nearer it is approached the greater will be the effect
produced. If the sitter be placed very close to the window and the
reflector a long way off, or if it project the light in a wrong
direction, it is manifest that in the resulting pictures the
shadows will, of necessity, be heavy, and the negative will have an
under-exposed appearance, however long may have been given, simply
because there was no harmony in the lighting of the model. In the case
where the picture has been flat it has arisen from the sitter being
placed too far back from the window, so that the direct light falling
upon him has been too feeble to produce any strong lights, and the
reflector arranged so that it received a stronger illumination than
the model, then reflecting it on to the latter, quite overpowering the
dominant lights. The remedy for this is simply to bring the sitter more
forward, so as to obtain a stronger dominant light.
With regard to the time of exposure: we must again impress upon the
student the necessity for placing the sitter as close to the window
as can be conveniently done, for then he will receive the strongest
illumination; and, no matter how strong the shadows which may be
produced, they can always be modified sufficiently by the judicious use
of the reflector. Of course, in practice there is a limit as to the
closeness the sitter can be placed, inasmuch as if too near there will
not be room enough for the background. As we have before said, the
effective light falling upon the sitter is governed by the amount of
direct skylight to which he is exposed. For experiment, let any one seat
himself, say, one foot from the window and sideways to it, and note the
amount of sky that can be seen from this position, then take a seat six
feet within the room, and note it from thence. The difference will be
very marked indeed, and it will fully account for the long exposure that
some have found imperative.
In our previous articles we directed special attention to the advantage
accruing from arranging the sitter in such a position that he received
as much direct light as possible, so that it practically helps to soften
the shadows; hence the sitter should be placed so that he is turned as
little away from the source of light as will enable the desired view of
the face being obtained. That this may the more advantageously be done
the camera should always be placed as close as possible to the side
wall in which the window is situated. As an experiment illustrating the
advantage of this: let a camera be placed close to the wall, then the
sitter arranged so that from that point of view a three-quarter face is
obtained, and it will be noticed that there is very little need of the
reflector at all. Let a negative now be taken, and the camera brought,
say, five feet into the room, and the sitter, without changing his seat,
turned round until a similar view of the face is obtained from that
point. It will now be seen that the shadows are very much deeper than
before, and the reflector will have to be brought pretty close in order
to overcome them; nevertheless they may be obtained quite as soft and
harmonious as in the former case. Let a second negative now be taken,
giving the same exposure as before, and it will be found that if
the first one were correctly timed the second will be considerably
under-exposed. Yet the sitter was at the same distance from the window
in each case.
This shows the advisability of utilizing all the direct light it
is possible to do, and thereby leaving as little as we can to be
accomplished by the reflector. When the sitter is arranged to the best
advantage at a window of ordinary size, fully exposed pictures can
generally be obtained with a portrait lens (full opening) in fairly good
light, on moderately sensitive plates, with one or two seconds' (or even
less) exposure. If a longer exposure than this be necessary, it
may fairly be assumed that the lighting has not been properly
managed.--_British Journal of Photography_.
* * * * *
A NEW METHOD OF PREPARING PHOTOGRAPHIC GELATINE EMULSION BY
PRECIPITATION OF THE BROMIDE OF SILVER.
By FRANZ STOLZE, Ph.D.
I consider the method of precipitation described below as far superior
to any other hitherto employed, particularly on account of its
infallible certainty. I began at first with a thirtieth of the whole
quantity of gelatine, and increased that quantity to a tenth without the
precipitate forming with greater difficulty. The salts were dissolved in
the usual quantity of water, the bromide of potassium was added to the
separately-dissolved gelatine, and both solutions cooled in iced water.
I soon found that even this was not necessary. I accelerated the
solution of the salts by vigorous agitation, so that the temperature
became so much lowered that, even after the addition of the warm
gelatine, it still remained low enough to give the precipitate when
mixed. The mixing took place gradually, all the usual precautionary
measures being observed; such as pouring the silver solution into No.
2 in small quantities at a time, and constantly stirring, and the
separation from the mother lye was complete.
The formula according to which I worked latterly was as follows:
SOLUTION I.
Nitrate of silver...................... 463 grains.
Water................................... 16¾ ounces.
SOLUTION II.
Bromide of potassium................... 355 grains.
Iodide of potassium..................... 15 grains.
Gelatine................................ 46 grains.
Water................................... 16¾ ounces.
After the mixing is completed the perfect separation of the precipitate
takes place in four minutes at most. The clear fluid may be decanted off
almost to the last drop, after which the precipitate is washed three
times with water. In order to dissolve the precipitate pour over it a
solution of 1.5 part of bromide of potassium in 100 parts of water,
agitate, and then add a solution formed of 8 parts of ammonia of the
usual strength in 600 parts of water. The emulsification will begin
at once without any further heating. When now heated on the water
bath--already at from 95° F to 104° F--the whole precipitate will be
suspended, and thin films of the emulsion, when looked through, will
have a grayish tint, but when dry they will appear partially red.
Digestion at 104° F is continued--from half an hour to an hour is
usually long enough--until the film, even when dry, remains violet
through and through. The remaining gelatine, 450 grains dissolved in 16
ounces of warm water, is then added, filtered, and plates coated with
the resultant emulsion. But if it be desired to prepare emulsion for
storage, wash the precipitate finally with alcohol, and store it either
under alcohol or dry it as usual. To use it dissolve in the manner
described above and mix with gelatine.
The great advantages of this process are evident. Not only is the
troublesome washing saved, but, what is more important, the great mass
of the gelatine is added to the emulsion in a condition which secures
to the film a hitherto unattainable firmness. Also, it enables one to
prepare a keeping emulsion with a minimum of alcohol, and, since the
quantity of gelatine in the original emulsion is so small, it dries,
when it is not desired to keep it under alcohol, so much more rapidly,
and thereby also furnishes a more constant preparation.
I am convinced that this process is as yet but in its infancy, and that
it is susceptible of great improvement. From the purely theoretical
standpoint, the property possessed by gelatine, of combining in
sufficiently cold solutions with bromide of silver in the nascent
state, and falling to the bottom in a flaky condition, is exceedingly
interesting. Evidently this property plays a part in the preparation of
emulsion which has not until now been recognized. I do not doubt that
it may be possible to effect, by a sufficiently low temperature,
precipitation even from solutions rich in gelatine, if experiments
in that direction were set on foot. What influence variations in
temperature may have upon the subsequent sensitiveness of the emulsion,
and whether the action of the ammonia and the bromide of potassium is
more energetic, in the absence of the elsewhere-present nitric salts,
are questions which can only be answered after thorough examination;
and the parts played by the various additions of iodide or chloride
of silver in this method of emulsification must likewise also be
ascertained by experiment. The object of this article is to point out
this rich province for research, and to induce experimenters to turn
their attention to it; for it is only after the behavior of emulsion
under all these conditions has been thoroughly examined that we can hope
to reap the best results from the new process.--_Wochenblatt_.
* * * * *