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The photographic news
- Bandzählung
- 35.1891
- Erscheinungsdatum
- 1891
- Sprache
- Englisch
- Signatur
- F 135
- Vorlage
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- Hochschule für Grafik und Buchkunst Leipzig
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- SLUB Dresden
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- urn:nbn:de:bsz:14-db-id1780948042-189100009
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- http://digital.slub-dresden.de/id1780948042-18910000
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- Bandzählung
- No. 1719, August 14, 1891
- Digitalisat
- SLUB Dresden
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Zeitschrift
The photographic news
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Band 35.1891
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Band 35.1891
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- The photographic news
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This same actinic power is modified by our use of the diaphragm in the lens. But here, also, some experiments of the past year have given us some new light. Dr. Michelke, of Germany, has shown that if we reduce the size of the opening in the lens to one-fourth, we shall have to increase the time of exposure not four times, as would be expected, but twenty per cent, more, or nearly five times. By using yet smaller openings we must add still more to the time, and with one thirty-sixth of the open ing the time will have to be forty-eight times as long, or an increase of one-third the calculated time for correct exposures with a corresponding larger stop. In a word, if the time of exposure is correct with a stop of one inch, and it is desired to use a stop of one-quarter of an inch, we must increase the time of exposure not four times, but nearly five times. Flash-light photography has many workers, and it is constantly being put to good use and its manner of applica tion being improved. Various devices have been em ployed to overcome the hard shadows that were to be found in the first pictures made by its use. The methods of doing this are in the division of the magnesium powder into a number of small charges, rather than using it in one large flash. These charges are fired simultaneously by the use of a number of gas-jets that are made to impinge on pieces of gun-cotton on which is placed the magnesium, the projection of the many flames at the same instant being controlled by some device that regulates the pressure of the gas and increases it at the same moment at every jet. Pictures made by these methods are very hard to dis tinguish from those made by daylight. The colour of the magnesium light is capable of much modification, and in this respect may be a most useful adjunct to the orthochromatic plates. Two German experimenters have applied this in photo-micrography, using a mixture of perchlorate of potash with magnesium, chloride of sodium, and tartrate of barium, with some excellent results. The development of the photographic plate has received a good deal of attention during the past year. In the matter of developers there is not very much to report, but quite recently paramidophenol, a substance related some what to eikonogen, has been proposed as a new agent. Like eikonogen, it is not very soluble, and it is also rather expensive, but if it is found to have any decided advan tage the chemist will soon find a way to make it cheaply. At the present time it is said to possess good developing powers, and its use gives no stains on the films. Com pared with eikonogen and hydrokinone, it oxidises more rapidly than either. It is consequently more active than these developing agents. But its most important advan tage is the fact that it will not colour the film, and can be used for a large number of plates in succession. It is said that as many as twenty plates may be developed in the same bath without causing the least stain on the nega tive. From these indications it would appear to be as rapid as pyro without its staining defects. In connection with the subject of developers, the in teresting experiments of Colonel Waterhouse deserve a moment’s attention. He has found that, by the addition of a very small quantity of thiocarbamide to the developer of eikonogen, it is possible to produce a positive image instead of a negative one. This is a matter of small im portance to the ordinary photographer, but to those who have to work the photo-mechanical processes it is a saving in the steps to be taken for the production of the final printing plate, for it saves the production of a positive from the usual negative. Coming now to the printing processes, we must record the revival of the use of gelatine as a substitute for albumen, with more improvements than it has seen in many years. Aristotype paper has made some very important advances during the past year. Platinum printing still holds its own with amateurs, and it would be a source of profit to the professional photographer in the better class of work if he would but take time to overcome some of the earlier difficulties. In Europe they are far ahead of us in this matter. A new printing process was presented to the photo grapher by two English chemists some months ago, which depended for its action upon the change made by light in the chemical structure of a dye-stuff made from the colour ing matter known as primuline. This substance has the curious property of uniting with different organic matters, and producing with each one a coloured print. If, there fore, we print in diazo primuline from a star-shaped nega tive, we can make each of the star rays of a different colour, by the use of different organic matters put on as developers in the form of paste. The application of photography to astronomy continues to give the most wonderful results. Stars unseen by the human eye are detected by the photographic dry plate. And some recent photographs made in Sydney, Australia, show that the stars of the Milky Way are really larger than they appear to the eye through the telescope. This is due to the fact that they emit many blue rays which are invisible to our sight, but whose light affects the photo graphic plate. Photo-mechanical printing processes have made import ant advances in colour printing, in which they are now producing some of the most beautiful work ever attempted by the aid of light and the printing press, and without the aid of the human hand. Such is a very rapid survey of the advances of our art since we last met. In the brief space that could be given in such a report as this, many really important steps of progress have received but a word of mention. • . The Eastman Company have issued, in connection with the late Buffalo convention, a very neat " Kodak Souvenir,” which takes the form of an artistically got up pamphlet comprising a number of specimen prints on the three different grades of bromide paper issued by this enterprising firm. The pictures are of various dimensions, and have been printed by gas-light. They are designed to show the different sizes in which the kodak camera is now issued. The subjects chosen for illustra tion consist of various views of the Convention buildings at Buffalo, some capital instantaneous Niagara views, and last, but by no means least in interest, the Eastman Company’s new works at Rochester, N. Y. With regard to these latter, we are informed that “ the new plant consists of fifteen acres, on which four buildings are already in operation, The largest of these buildings is devoted exclusively to the manufacture of the ‘Eastman Transparent Film ’; the dimensions of the build ing are 300 by 100 feet, which will give some idea of the capacity for turning out this product alone. The other build ings consist of laboratories, emulsion rooms, carpenter and machine shops, boiler and engine rooms. The power house contains a 75 horse power compound engine, which runs two Eickemeyer dynamos—electricity being used throughout the factories for light as well as power to run all the machinery—■ and a 50-ton De La Vergne ice machine, which is employed to keep the emulsion and film rooms at a cool, even temperature. Space is left for other engines, as several other buildings are under consideration, which, when finished, will undoubtedly make this the most complete plant of its kind in the world.”
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