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The photographic news
- Bandzählung
- 7.1863
- Erscheinungsdatum
- 1863
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- Englisch
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- F 135
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- Hochschule für Grafik und Buchkunst Leipzig
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- Hochschule für Grafik und Buchkunst Leipzig
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- Bandzählung
- No. 253, July 10, 1863
- Digitalisat
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Zeitschrift
The photographic news
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Band
Band 7.1863
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- Titelblatt Titelblatt -
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- Register Index 619
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Band
Band 7.1863
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332 THE PHOTOGRAPHIC NEWS. [July 10, 1863. sitting, the knee and part of the leg will be visible. If this be not so, the pose would be bad, and present to the eye an unpleasant incompleteness; for the same reason, the hands and arms should be full in view. In the bust portrait,the person is represented as far as the chest, without either the hands or the arms. In this case, the head is everything, and the bust is merely represented to sustain it, and give it its true size and proportion. If the bust be too large, the eye of the spectator naturally desires the arms, hands, &c. One must, however, be very careful not to fall into the opposite excess, by giving too little of the bust, as the head would appear quite out of its proper proportion ; the nature of the model is the surest guide as to the importance to be given to the bust. The modifications that you can obtain, by means of contrast, are important aids for obtaining resemblance and increasing beauty. It follows, from what we have just seen, that the head should never be represented without the bust. The effect of such a portrait is altogether devoid of correctness and unity, and does not offer a single point of comparison by which the spectator could judge of the proportions of the head with respect to the rest of the body ; a matter of much im portance, as this is one of the most striking characteristics of the individual. (To be continued.) ! STEREOSCOPIC MANIPULATIONS IN THE FIELD* Tub plates which I use for the reception of the stereographic negative are seven inches long by three inches and a half wide. By having the plates somewhat larger than absolutely required, allowance is thus made for any defect that might be visible on the ends or edges, which are more liable to such than the central parts; for if it should happen that the glass corners of the plateholder have not been thoroughly cleaned before the insertion of the sensitized plate, or that the silver solution has not been allowed to drip off after it has been withdrawn from the bath, the fluids in the corners (especially if these are cemented and not wholly of glass) becomes readily decomposed by the lac or resin with which the pieces are cementedt, and by capillary attraction arises along either end, and moves on the lower horizontal edge, and produces a reduction of the silver in these parts, as if the film were marbled. Such an occurrence is very troublesome, and ought to be avoided, and can be avoided in general as follows:— Clean the glass corners thoroughly every time before the introduction of a new plate; allow all extraneous silver solution to run off into the bath before the plate is entirely removed from it; finally, with a piece of blotting paper or an old rag, carefully remove all fluid from the posterior surface of the plato and corners. In the last operation it requires great caution lest any part of the protuberant portions of the blotting paper or rag should, by the quick motion, lap round the edges, and thus disturb the collodion film. As soon as all extraneous silver solution has thus been removed (and, of course, all these operations have to be performed in darkness), it is placed in the plateholder and inserted in the camera. I need scarcely remark here that the interior of the camera must be quite dark; in field-work, that is, outdoor-work, a mere pin-hole would allow sufficient light to penetrate so as to destroy the best negative by fogging the whole surface; and not only must the interior be quite free from the ingress of light, but all the parietes must be stained or coloured of a dead black, as also the inner surface of the tubes containing the lenses. The greatest care, in like manner, is required in drawing out the slide and again in replacing it, after the collodion film has been impressed with the image, in order to exclude every ray of diffused light. It is well, therefore, to throw over the upper surface of the camera a large black cloth, so that, in drawing out the slide, the amateur seizes it together with the cloth, and draws both up or sideways at the same time. The focussing cloth, as an auxiliary in this respect, is left on the posterior end of the * Humphrey's Journal. t Silver-wire corners are almost universally used in this country, which prevent the trouble referred to. camera to keep out all light that might penetrate through any crevice in the grooves in which the plateholder slides. By never omitting such cautious manipulations, many an incon venience and unexpected disaster will be avoided, which are frequently attributed to the collodion, the bath, or the deve loper. Another caution in landscape photography or stereography is to avoid exposing the plate too long; if the lenses be good ones, that is, well corrected aplanatically and achromatically, four or five seconds, for a lenticular aperture of an inch and a half and a diaphragmatic opening between the lenses of half an inch, will be found, in general, sufficiently long, and frequently much too long. Stereographic negatives in the field seldom require more than two seconds with such a stop ; in fact, some times when the weather is very fine, the air quite clear and totally free from any haze, a quarter of a second will produce a very respectable negative. Let the circumstances be as just described, and let a plate be exposed for thirty seconds; a pic ture will probably be produced that might mislead the beginner and induce him to lengthen the time. On the contrary, let the student begin with one second; if the picture comes out quite distinctly in all its parts, with a proper contrast between the lights and shades, and containing, besides, the middle tints, the time, probably, will bo quite sufficient, especially if the negative has to bo intensified afterwards. Where the proper opacity is to bo developed by the first operation, a longer time is required. In this case a very weak developer must be used, otherwise the development will be quite unmanageable; as soon as the slightest appearance of fogging in the high lights be comes visible, the plato must be instantaneously washed. By shortening the time, the operation of development is entirely within the control of the artist; and the intensification after wards can equally easily be regulated. The process of intensi fying can bo performed either immediately, that is, before the plate is dry or any time afterwards. It seems to me to be a good practice to perform this operation after the labour of out door work, at a time when there is no hurry, and where there is every convenience. For such purposes the edges of the nega tives have to be varnished by running the side of a glass rod, dipped in varnish, all the way round so that the collodion film becomes covered in width of one-tenth of an inch with this glutinous and protecting substance. The varnish is then allowed to dry spontaneously. So treated, the plates can bo hoarded away and strengthened at any convenient opportunity. Supposing the day and moment have arrived when the nega tives have to be intensified. The plates are immersed in soft water and kept there for at least half an hour; in this time the film has become softened and impregnated with water, and is thus rendered suitable for the action of the intensifier. Intensifying PROCESS. It is supposed that the negatives are suitable for intensifying and have been thoroughly washed, and, if dry, thoroughly soaked. If there be no middle or intermediate shades in the given negatives it cannot be expected that the intensifier will produce that which already has no existence. The office of the intensifier is to thicken and darken the shades and half shades that have already appeared under the developer, but not to produce shade and half shade. The process, therefore, is two fold, consisting in thickening the existing deposit, and then in darkening the thickened deposit. To Thicken the Actino-Silveb Deposit on the Collodion Film. The shades receive a deposit, as it were by galvanic action, in various ways. In the first place, if we pour on the wet sur face of the negative a solution of bichloride of mercury quickly, so that the action can commence simultaneously in every part of the negative, it will be found that the shades increase in opacity and become more and more dense. Secondly, flow the plato with a dilute solution of the red iodide of mercury dissolved in iodide of potassium until the same result is obtained. (Iodide of mercury can bo bought, or prepared as follows:—Drop a solution of iodide of potassium into one of bichloride of mercury as long as a red precipitate is obtained; as soon as this precipitate has subsided, pour oil the supernatant liquid, wash well and several times with water, and again pour off all the liquid above it. Now drop upon tho pre cipitate a saturated solution of iodide of potassium until the red-coloured substance is entirely dissolved, and the solution
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