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The photographic news
- Bandzählung
- 27.1883
- Erscheinungsdatum
- 1883
- Sprache
- Englisch
- Signatur
- F 135
- Vorlage
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- SLUB Dresden
- Lizenz-/Rechtehinweis
- Public Domain Mark 1.0
- URN
- urn:nbn:de:bsz:14-db-id1780948042-188300004
- PURL
- http://digital.slub-dresden.de/id1780948042-18830000
- OAI-Identifier
- oai:de:slub-dresden:db:id-1780948042-18830000
- Sammlungen
- Fotografie
- LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
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- Parlamentsperiode
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- Bandzählung
- No. 1281, March 22, 1883
- Digitalisat
- SLUB Dresden
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Zeitschrift
The photographic news
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- Titelblatt Titelblatt I
- Register Index III
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180 THE PHOTOGRAPHIC NEWS. [MARCH 22, 1883. completely within the control of the operator, and effects are obtained that cannot be secured in any other way. The studio examined is at the end of a low, dark store on the ground floor, and there is no dependence whatever upon day light. Upon the sides of the room near the ceiling are two tracks carrying a wooden car that reaches from side to side of the room. On this car are laid tracks for a smaller car, that travels on across the room in the opposite direction. The arrangement, it will be seen, is the same as that used in stone-yards and machine-shops, and known as an overhead crane. On this crane is suspended a powerful arc light, and, by pulling cords at the side of the room, the light can be moved to any part of the ceiling, or raised and lowered, as may be desired. In front of this crane is another having only one motion, across the room, the car on top carrying five arc lights suspended beneath it. This crane is also controlled by cords in easy reach of the operator. The subject sits in front of these six lights, and by moving the lamps perfect control of the illumination is secured. The light may be concentrated at one side, or spread out in front, or distributed in any manner that the artistic treat ment requires. To secure still more complete control of the light, a platform is placed in the middle of the room before the lights. This platform is large enough to contain a seat for the subject and the camera. It is also pivotted at the centre, so that it can be turned completely round in a horizontal plane. In taking a portrait, the subject sits upon the platform facing the camera, and the lights are raised, lowered, or moved about till just the effects of lighting that are desired are obtained. Th operator stands on the floor behind the camera, with one hand resting on a handle fastened to the platform. The instant the ex posure begins, the operator slowly turns the platform round, keep ing it in motion while the exposure lasts. It is plain that the camera keeps the same relative position to the subject during the time of exposure and while the platform is moving, while the re lation of the subject to the light is continually changing. This arrangement gives a continually shifting play of light on the sub ject, and secures a portrait having a fine gradation of tone and excellent modelling of the features. Only dry plates are used with the apparatus, and the exposure is a trifle longer than with daylight. To secure a like degree of definition the plate must be exposed five seconds, where a dry plate in sunlight would require three seconds. The portraits made by this arrangement of electric lights were marked by an excellent degree of finish, so that retouching did not appear to be necessary. The complete control of the light makes it possible to carry on work at all hours of the day or night, and in any weather. For copying, the electric light appears to be excellent, a single arc lamp with a reflector of white paper being all that is required. PHOTO-LITHOGRAPHY AND PHOTO ZINCOGRAPHY. BY MAJOR J. WATERHOUSE, B.S.C., Assistant Surveyor-General of India. Chapter VII.—Production op the PHOro-TRANSFEE Print. Exposure to Light.—The sensitive paper, having been pre pared by any of the methods described in the last chapter, has next to be exposed to light under the negative. For this purpose the ordinary pressure frame used for silver printing will answer; but, as considerable pressure is re quired to produce the very close contact with the negative which is necessary in reproducing line-work, it is desirable to have additional springs fitted at right angles to the back cross-bars, so that the pressure may be thrown more evenly all over the back of the frame. Some operators prefer the printing frame to be fitted with screws instead of springs, and the cross-bars carrying the screws may with advantage he made movable, so as to enable more or less pressure to be applied at any desired point. As the exposure is very short, and can generally be judged sufficiently well by the appearance of the edges of the paper beyond the negative, there is no necessity for examining the progress of the print during exposure ; and it is best not to do so, if possible, on account of the tendency to doubling of the image by contraction, or expansion of the very hygrometric gelatinised paper. The back of the printing frame may consequently be rigid, instead of being jointed in the usual manner; and it is a good plan to cover the sensitive paper with a sheet of patent plate glass, placing over this sufficient paper or felt padding to produce a good pressure when the frame is closed. The frames and pads must be thoroughly dried before use, otherwise, if they are damp, the gelatinised paper is liable to stick to and destroy the negative. In damp weather it is a good precaution to brush a little French chalk over the sensitive paper and negatives. For line-work it is better to expose in sunlight when available, taking care to place the frames perpendicularly to the direction of the solar rays, so that any possible diffu sion of light may be minimised. When printing in the shade, the same object is gained by placing a black canvas screen round the printing frame to a height of about 2} to 3 feet. The duration of the exposure will, of course, depend on the quality of the negative, the sensitiveness of the paper (as regulated by the quantity of bichromate in it), and the chemical intensity of the light. With a clear, strong nega tive, very sensitive paper, and strong sunshine, from half-a- minute to two or three minutes will be enough. In dull weather, or with bad negatives, the time may be increased from five to twenty minutes, or longer. When properly exposed, the outside borders of the paper beyond the negative should appear of a greenish brown, and the lines of the print of a clear reddish brown on a bright yellow ground, the finest lines being well visible. Though the image should be well brought out, it must not be over printed so much as to affect the white parts, or it will be difficult to get them clean in washing, especially if inked in the press ; the lines also will retain too much ink, and give a heavy transfer. On the other hand, if the print be under exposed, the flue lines will be liable to be washed away, and the transfer will be weak. The exposure may be rather more with hand-inked prints than with press-inked. Husnik recommends exposing till a spot painted out in the dense open part of the negative appears just lighter on the yellow ground than the surround ing ground. An actinometer may be used if thought necessary, but in practice sufficient experience is soon gained, especially if the conditions of exposure are tolerably constant—either sunshine or shade—and the negatives of fairly even quality. During the exposure it may be advisable to shsde off with a cloth or hankerchief the clear and open parts of a negative, while the denser and closer parts, which may perhaps be covered with a slight deposit, receive more exposure. With the same object Mr. Bolas recommends that a piece of fine tracing paper should be stretched at the back of the negative and shaded with blacklead, applied with a stump in such a manner that all the lines may appear about equal in trans parency. If necessary, the tracing paper over the denser parts may be made more transparent by means of a little varnish, or a piece of the tracing paper may be cut out with a knife. This mode of working is chiefly necessary when copying engravings or other subject, with very fine lines, and is seldom required with strong black and white subjects. Gare must be taken not to expose the sensitive paper to light when putting it into or taking it out of the frames, and on no account must prints be examined in daylight. Ink'ng of the Print.—Having now obtained the photogra phic print, the next proceeding is to give the lines forming the design a thin coating of greasy ink, so as to transform the print into something similar to an ordinary lithographic transfer drawing or print. As noticed before, there are two ways of doing this, which may shortly be called the ‘'washing-off” and the "inking- up "methods. In the first, the whole surface of the collo-chromate print is covered with transfer ink, and the print is then washed either in hot or cold water, according to the nature of the colloid substance employed for the preparation of the paper.
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