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The photographic news
- Bandzählung
- 27.1883
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- 1883
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- Hochschule für Grafik und Buchkunst Leipzig
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- Bandzählung
- No. 1285, April 20, 1883
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APRIL 20, 1883.J THE PHOTOGRAPHIC NEWS. 245 pair. A neat ankle, and indeed a great part of the foot, is seen when wearing sabots, and we feel quite sure that any photographer who is acquiring a wardrobe with a view to produce studies and pictures, could make good use of such objects. In any case, they afford a way out of a difficulty which, judging from past results, is one that has spoilt many a promising picture. PHOTOGRAPHING THE “ SOFT PALATE.” BY EDWIN COOKING. In reference to some photographs taken by me in October last year (1882) of the “ soft palate” (a transparency from one having been shown by the optical lantern at the last meeting of the Photographic Society of Great Britain), I may state that having gone through some experiments on two evenings only, I have not had further opportunities for taking advantage of the limited experience thus gained. On both occasions the oxy-hydrogen lime light was used as the illuminating power, two lights being in use at the same time ; and in consequence of its being found necessary to bring both lights so very close to each other, for the pur pose of preventing one side of the interior of the mouth, and also the soft palate, from being in strong shadow, great difficulty was experienced in placing the camera, with a No. IB lens, close enough to get a large image, which was wanted; also, unfortunately, no head-rest was at hand to keep intact the position of the sitter, whose face was so close to the lime burners that the powerful light was very trying to his eyes, as also that the heat tended to produce an involun tary motion of the head. Under these circumstances my first experiments were made, and some half-dozen negatives were taken and developed ; the result being a very soft palate indeed—in fact, more like wool. On the second evening a head-rest ‘was used, and the negatives were then to be taken as small as possible (and I may here observe that I think that in this matter of small negatives will lay one of the elements of success in this work). I had in the interim fitted up a camera, so that it could take six pictures on a half-plate ; but it being found desirable that the two lights should be brought still closer together, and, consequently, the camera having to be placed farther off from the sitter, I was compelled to put that arrangement on one side, and use a No. 2B lens, which at the distance of six or seven feet gave an image of the mouth about one quarter of an inch in diameter. After taking and developing one negative, which proved successful, nine other negatives were then taken (but not developed at the time) in different positions according to the pitch of sound which was given out by the sitter whilst the photograph was being taken. There was no opportunity given for attempting to photograph the vocal chords (situated down in the throat), in consequence of the difficulty of placing the mirror of the laryngoscope (held at the back of the mouth) in the right position, so that the invisible might be made visible. A glimpse of these delicate organs was now and then seen upon the focussing screen, but so fugitive that they were here, and gone again. It was at this point that it became evident to me that, with the direct transmission of light from the lime burners, it would be almost impossible to secure the proper incidence of the rays of light upon the mirror, so that it might be reflected down the throat, and any further attempts were given up for that occasion. Even for taking the soft palate, it was necessary that a mirror or plane looking-glass should be placed in front of the sitter just over the direct line of the centre of the lens, so that the sitter himself could see approximately when the right position was attained ; but the actual moment for exposure was indicated by a medical gentlemen present, who also knew perfectly well what was desired to be re presented. The exposures were made by a pneumatic shutter inside the camera, which was prevented from open ing downwards further than just below the centre of the lens ; and it soon became evident to me, whilst these ex periments were going on, that when the “ laryngoscope ” came to be used, the image seen on the looking-glass must be directly in the line of the centre of the lens, and I then thought of some arrangement which might be made. By using another pneumatic shutter, with a looking-glass attached to it, placed outside the lens, or fixed nearer the sitter, and by uniting the two tubes at some part with a Y-shaped metal tube, one pressure upon the bulb would set in motion the two shutters simultaneously, the sitter himself could then make the exposures, and a most impor tant difficulty be overcome ; as also that the two shutters moving in opposite directions, the inside one going down, whilst the outside one went up, during the opening, and vice versa during the closing, would greatly assist, if neces sary, in making the exposure shorter still. I had scarcely turned over in my mind what the necessities of the work required in the future, when—my experiments came to an end. HARDWICH ON THE LIME LIGHT. BY T. F. HARDWICH, M.A.* In using a biunial or a pair of lanterns for the production of dis solving views, a common defect is, that the two pictures are not of equal intensity. Supposing the focal depth of the lenses and condensers to be the same, the fault is usually to be found in the jets. In the case of the oxyhydrogen or mixed gases the nipples of the jets should be bored with great care, or there will be a small but appreciable difference in the pictures. The last eighth or tenth of an inch of the bore should be very smooth and uniform in size throughout. If it be at all conical, tapering, and becoming smaller towards the orifice, or, worse still, as I have seen in one instance, tapering away from the orifice, the light will not be so good. The orifice itself, also, should have a sharp edge inwardly to direct the stream of gas, and should not be rounded off or trumpet-shaped. When I find this to be the case I rub down the point of the nipple on a dry hone, such as boys use for sharpening knives, until a clean edge is obtained, and then guage the orifices with a needle to satisfy myself that they are of the same size. In the blow-through process (the term" blow-through” is not euphonious, but I know of no other so accurate or expressive) an inequality of illumination is often due to a contraction at some part of the hydrogen tube of one of the jets. It should be borne in mind that the pressure of coal gas drawn from the main is comparatively low, and hence the passage should be kept well open. By drawing air through the two jets with the mouth you will perhaps observe that it passes less freely through the one which gives the feeble light; and when the bye-pass hydrogen is turned down low, that lantern will go quite out in dissolving. On trying a new biunial lantern I once noticed that, although the two blow-through jets were to all appearance exactly alike, the one gave a brighter disc than the other. They were “ inter changeable ” jets, and on examining them carefully, I discovered a leak in the one which gave the stronger light. The plug sepa rating the oxygen from the hydrogen was not absolutely tight, but allowed a little of the former gas to pass into the latter. It occurred to me that if I were to rime out a small channel in the plug of the other jet until I found by suction that the two corres ponded, I should remedy the defect; and such proved to be the case, for the pictures became at once of equal intensity and un usual brightness. I thought at first that I had stumbled upon an improvement; but further experience showed that great care was needed in making this channel of communication between the oxygen and hydrogen of the right size, and that if it were at all too large the flame tended to pass backward and could not be kept burning at the mouth of the jet. A few candles more or less in illuminating power are of small consequence compared with simplicity and certainty of manufacture, and hence I content myself at present with stating the fact that, if a minute quantity of the oxygen should leak into the coal gas at a point lower down than the outlet, it will cause that jet to give a brighter disc than the other. A great deal of useful information can be gained by looking in at the front glass of each lens whilst the lanterns are burning, • Read before the Newcastle-on-Tyne and Northern Counties’ Photo graphic Association.
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