Towler, John. The Silver Sunbeam. Joseph H. Ladd, New York: 1864. Electronic edition prepared from facsimile edition of Morgan and Morgan, Inc., Hastings-on-Hudson, New York. Second printing, Feb. 1974. ISBN 871000-005-9
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HEREAFTER I shall devote a chapter to the stereograph and its philosophy; in this I shall simply give plain instructions for taking the stereoscopic negatives by the wet collodion process. Form-door work, and for out-door scenery where the objects are close at hand, a camera is required, which is furnished with two lenses of short focus, and of exactly equal power, for the production of stereoscopic negatives. These lenses are fixed in the same horizontal line; and about two inches and a half is the distance between their centers. Each lens can be attached to a separate slide, so that this distance can be slightly increased to two inches and three quarters, if found necessary. In the camera there is a vertical septum in the middle which divides it into two halves, one for each lens. This septum is nearly in contact with the collodion, and consequently makes a division line between the two images, which are taken on the same glass. The glasses for stereoscopic negatives are seven inches long by three and a half wide; I should prefer them eight inches by four, in order to have room for blunders and mishaps on the edges. The operation of focussing is the same here as before, only that there are two lenses to be adjusted. Fix upon a certain object which is to be the central or most important one, and turn the camera so that it is seen in the center of one of the pictures of the ground glass. Where architectural objects occur in such pictures, the camera must be perfectly horizontal, if you intend the vertical lines to be vertical in the negative. If it happen that such architectural objects can not easily be comprehended in the negative, without tilting the camera, use this expedient; for, after all, the distortion which it produces on the print can be rectified in some measure afterward, by tilting the print in the stereoscope to the same amount. If portraits are to be the principal things, they must be placed in such a position artistically and photographically as to appear well, and at the same time in perfect focus; if certain objects are to be pre-eminent in esteem, direct your attention upon them when focussing, and regard the rest as secondary; and finally, if the whole landscape is the object, divide up the focus, or focus in such a manner that the view as a whole is tolerably sharp; this can easily be done by focussing an object at some distance, and by excluding all near objects from the print. In such cases, however, we require long-focussed lenses. For in-door operations the portrait combinations are used; for landscapes a pair of triplets, or of ordinary view lenses, produce excellent results. The globe lens of C.C. Harrison is all that can be desired for field work; it comprehends a larger angle than almost any other lens, and produces an irreproachable picture. Ross, Dallmeyer, and Grubb manufacture stereoscopic lenses for landscape photography, with which instantaneous pictures can be produced, and which in all other respects are highly commended by the intelligent amateurs of Great Britain. Jamin's view-lenses produce very neat results, and are besides lower in price than those already alluded to.
In the ordinary stereoscopic negative, as in every negative, the pictures are laterally inverted, and when printed, this inversion is corrected only for each picture individually, for the right-side picture is still inverted and in the place of the left-side picture. In consequence of this, the printed stereographs have to be cut apart, and mounted so that the right-hand photograph is placed on the right side, and the left hand photograph on the left side. When taking pictures of still life, as also others, where the living objects are not in motion, it is very easy to manage matters so as to invert the photographs on the negative. The method is as follows: Take a large-sized camera-stand, allowing sufficient space for the camera to slide laterally. Placing the camera in the right-hand corner, focus the left-hand lens. Next slide the camera gently, or lift it up and place it in the left corner, and focus the right-hand lens. The space between the centers of the two pictures thus focussed must be about two inches and three quarters. Whilst the camera is in this position on the left side, insert the sensitized plate, take out the slide, uncover the right-side cap for a second or two, and take this picture. Then close up the lens, lift up the camera gently and place it on the right side. In this position uncover the left-side lens for the same length of time. In this way, and in the space of ten seconds or so, the two pictures can be taken in a proper condition for printing so as to produce a non-inverted stereograph. For such work it would be no difficult task to contrive a slide by which a single lens would be all-sufficient; that is, when the camera is on the left side, the lens must slide to the right side, and vice versa on the right side.
As soon as the negative is this taken, it has to be developed before it gets dry. The development and fixing can be performed in a dark tent specially arranged for such purposes. Various contrivances have been adopted in landscape photography for these operations. For my own part I consider a simple hand-cart, with iron rods from corner to corner diagonally, in the form of semi-ellipses, and covered with a balloon-shaped tent, a very practical accommodation. But each successful photographer is somewhat of a genius, and can easily arrange a dark chamber according to his own taste and materials on hand.
Negatives thus taken and fixed are placed carefully away in slides where they can not be injured during transportation home. In the evening, or the next day, or at any convenient time, the negatives are examined; if clear, transparent in the lights, and sufficiently intense in the shades, they are varnished. On the contrary, if the opacity of the shadows is not deep enough, although the appropriate gradation exists between the lights and shades, it will then be deemed necessary to proceed to intensification. Previously the edges of the negatives must be varnished to the depth of one tenth of an inch upon the collodion, to prevent its peeling off during the operation. This is effected by dipping the quill end of a feather into the varnish, and then running along the edge of the collodion and of the glass, with this portion of the feather slightly inclined, so that the varnish does not drop oil; a sufficient quantity is attracted upon the collodion as you proceed. After this put the negatives aside, that the varnish may become thoroughly dry and hard. As soon as it is dry, immerse the plates in rain-water, and allow diem to remain there for about a quarter of an hour, by which time the collodion film will have become saturated iv with this fluid. Now you map commence the intensifying process, as before described in the chapter on collodion negatives.
There is no branch of photography that has so intensely attracted the attention of wealthy and intelligent amateurs as that of stereography; on this account we owe to them most of the discoveries in the art; and the new incitement that has arisen in this department, that of Instantaneous Actinism, has communicated a new impulse from which we derive fresh deductions and new results. The co-laborers in stereographic pursuits in Europe, but more especially in Great Britain, beginning with royalty downward to the rural gentry, are very numerous, very intelligent, and, best of all, very communicative. They take out no patents for their discoveries, they make no commerce with secrets, odious things which noble minds eschew. It is to such a goodly host of fellow-soldiers in the stereographic camp that we must attribute the riches of our knowledge. That light can act actinically in the twinkling of an eye is no tax upon cultivated conceptions; for in this same wink, which to us is instantaneous, Light has run round the earth several times; in this twinkling, Light has seen more than man in his age can ever see; in this twinkling, millions of fresh portions of light have impinged on the model, and have rebounded to the lens and through it, and have nestled upon the sensitized film-we are justified then in expecting that instantaneity in photography is feasible. The sole questions present themselves
What film is sensitive enough to receive it? What developer refined enough to produce the redaction? The questions are answered by facts. Instantaneous stereographs exist in great number, and the artists that produced them have bequeathed to the public their modus operandi. I can not do better than quote a few instantaneous processes. All amateurs agree in certain particulars, which conduce to success. The light must be very bright,, the atmosphere very clear; the glass very clean; the collodion very ripe; the developer very sensitive, and the lens very well corrected, and capable of producing a sharp picture with, a large diaphragm; the shorter the focus the better within proper hounds.
|Alcohol, spec. grav., .802,
|Iodide of lithium,
|Bromide of lithium,
The pyroxyline is first steeped in the iodo-bromized alcohol, and the ether then added.
|Re-crystallized nitrate of silver,
Iodized by leaving a couple of coated plates in the bath for several hours; acidified at the rate of from two to three drops of nitric acid to the ounce of bath. Leave the plate in the bath loner than you would if the collodion contained only iodine.
|Sulphate of iron,
|Acetate of lead,
Mix the above solutions, and when the precipitate has all settled, decant off very carefully, and then add
|Formic acid, (Pure,)
From this stock-developing solution take as much as is required, and add acetic acid, according to the temperature, generally in about the same quantity as the formic acid. The developer is kept on the. plate until the necessary detail is brought out; alter which the plate is well washed and fixed with a weak solution of cyanide of potassium.
Pour on a saturated solution of bichloride of mercury; as soon as the proper color is attained, the plate is thoroughly washed, and a five-grant solution of iodide of ammonium in water is poured on and off' until the desired depth has been attained. (The reader will comprehend the rationale of this proceeding by carefully perusing my remarks on this subject in a preceding chapter.) After this the following solutions are used
|Nitrate of silver,
Pour a few drops of No. 2 into No. 1, and pour on and off until the negative has assumed the required density. After which wash the plate thoroughly in several waters, dry and varnish.
Valentine-Blanchard prefers a bromo-iodized Collodion, although, under certain conditions he admits that a simply iodized collodion is more rapid, but at the same time there is less contrast. The silver bath is composed of re-crystallized nitrate of silver, forty grains to the ounce of distilled water, and saturated with iodide and bromide of silver. It is always supposed to he acid, to which is added a small quantity of moist oxide of silver; after the solution has been sufficiently agitated, it is filtered, and then acidified by a weak solution of nitric acid, containing three or four drops of acid to one hundred of water. This acid solution is added very cautiously, until the picture is quite clear and free from fogging. A bath so prepared is very sensitive whilst new, and it is only whilst new that any bath is likely to produce instantaneous results.
The developer consists of the sulphate of the protoxide of iron, generally thirty, and frequently fifty grains to the ounce of distilled water, acidulated with glacial acetic acid, because the ordinary acid contains impurities.
The negatives, when they require it, are intensified with a saturated solution of bichloride of mercury in cold water, until the film is of a uniform gray color; they are then washed and treated with a solution of iodide of potassium, (one grain to the ounce of water,) by pouring it on and off; until the film assumes a greenish-slate color. There should be no greenish hue on the wrong side of the plate, for this is an indication that the strengthening has been carried too far.
Hockins uses simply iodized collodion; his bath contains thirty grains of nitrate of silver to the ounce of distilled water, and is iodized by throwing in a proper quantity of iodized collodion; it is then filtered. Two minims of pure nitric acid are added to each eight ounces of the bath, which is prepared twenty-four hours before using.
The developer consists of
|Formic acid, (strong,)
This is kept on the plate until the operation is complete.
The means by which light is cut off instantaneously, which means very quickly, are various and many of them are very ingenious. Some of these shutters are behind the posterior combination in the lens, and are so graduated for other than instantaneous purposes as to give a shorter exposure to the sky than to the foreground. For my own part I prefer simplicity, and I use means in which I have been anticipated by Wilson and others. My cap is my shutter. Sometimes I use a book. With both I have succeeded, and naturally suppose others can do the same. I do not despise the ingenious shutter.
In very many cases, with all the preparations in a normal condition, as we suppose, success does not attend our manipulations. There is still, therefore, a yearning for some method more reliable. I have frequently succeeded in taking instantaneous positives, that could not be intensified into respectable negatives. But from a collodion positive we know that a collodion negative can very easily be prepared by copying. In this way many a well-valued view is obtained, which otherwise would have to be sacrificed. On such occasions, therefore, where there is the least doubt of success, it is advisable to develop with the ambrotype developer, containing nitrate of potassa, nitrate of silver, and free nitric acid-the latter, however, in very minute quantity. We shall thus probably obtain a good collodion positive on a melainotype or ferrotype plate. This is afterward carefully copied into a negative. In several instances I have obtained a tolerable effect by using solution of sulphate of iron without any acid.
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