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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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Zeitschrift
The photographic news
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Band
Band 27.1883
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- Titelblatt Titelblatt I
- Register Index III
- Ausgabe No. 1270, January 5, 1883 1
- Ausgabe No. 1271, January 12, 1883 17
- Ausgabe No. 1272, January 19, 1883 33
- Ausgabe No. 1273, January 26, 1883 49
- Ausgabe No. 1274, February 2, 1883 65
- Ausgabe No. 1275, February 9, 1883 81
- Ausgabe No. 1276, February 16, 1883 97
- Ausgabe No. 1277, February 23, 1883 113
- Ausgabe No. 1278, March 2, 1883 129
- Ausgabe No. 1279, March 9, 1883 145
- Ausgabe No. 1280, March 16, 1883 161
- Ausgabe No. 1281, March 22, 1883 177
- Ausgabe No. 1282, March 30, 1883 193
- Ausgabe No. 1283, April 6, 1883 209
- Ausgabe No. 1284, April 13, 1883 225
- Ausgabe No. 1285, April 20, 1883 241
- Ausgabe No. 1286, April 27, 1883 257
- Ausgabe No. 1287, May 4, 1883 273
- Ausgabe No. 1288, May 11, 1883 289
- Ausgabe No. 1289, May 18, 1883 305
- Ausgabe No. 1290, May 25, 1883 321
- Ausgabe No. 1291, June 1, 1883 337
- Ausgabe No. 1292, June 8, 1883 353
- Ausgabe No. 1293, June 15, 1883 369
- Ausgabe No. 1294, June 22, 1883 385
- Ausgabe No. 1295, June 29, 1883 401
- Ausgabe No. 1296, July 6, 1883 417
- Ausgabe No. 1297, July 13, 1883 433
- Ausgabe No. 1298, July 20, 1883 449
- Ausgabe No. 1299, July 27, 1883 465
- Ausgabe No. 1300, August 3, 1883 481
- Ausgabe No. 1301, August 10, 1883 497
- Ausgabe No. 1302, August 17, 1883 513
- Ausgabe No. 1303, August 24, 1883 529
- Ausgabe No. 1304, August 31, 1883 545
- Ausgabe No. 1305, September 7, 1883 561
- Ausgabe No. 1306, September 14, 1883 577
- Ausgabe No. 1307, September 21, 1883 593
- Ausgabe No. 1308, September 28, 1883 609
- Ausgabe No. 1309, October 5, 1883 625
- Ausgabe No. 1310, October 12, 1883 641
- Ausgabe No. 1311, October 19, 1883 657
- Ausgabe No. 1312, October 26, 1883 673
- Ausgabe No. 1313, November 2, 1883 689
- Ausgabe No. 1314, November 9, 1883 705
- Ausgabe No. 1315, November 16, 1883 721
- Ausgabe No. 1316, November 23, 1883 737
- Ausgabe No. 1317, November 30, 1883 753
- Ausgabe No. 1318, December 7, 1883 769
- Ausgabe No. 1319, December 14, 1883 785
- Ausgabe No. 1320, December 21, 1883 801
- Ausgabe No. 1321, December 28, 1883 817
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Band 27.1883
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476 THE PHOTOGRAPHIC NEWS. [JULY 27, 1883. arriving home, and if the result is moderately good, unless the subject is near at hand, nine-tenths of photographers would content themselves with it, and not take the trouble to return and get a result as nearly perfect as possible. This is another reason why better pictures are generally obtained by the wet process. The advantages of dry plates over wet must be obvious to every unprejudiced person : there is no cumbrous dark-tent, bath, dishes, &c., to be carried wherever you go, in addition to the camera; but only the dry plates, which occupy very little more space than the bare glass in the wet process. No experienced help need be employed ; therefore a reduction of expenses and good pictures may be taken at times when it would be absolutely impossible to take anything worth printing by the wet process. Any length of time may elapse between the time of placing the plate in the dark-slide and the ex posure, so that a proper lighting of the picture may be waited for, and therefore a good picture may nearly always be eecured; whereas in the wet process, a com paratively short time may elapse between the time the plate is taken from the sensitizing bath and the exposure (these advantages are on the assumption that the operator knows what he is working with). Besides facilitating the production of pictures, dry plates bring landscape photography within the reach of a great many amateurs who would otherwise do very little else than portraiture, and enables them to take their photo graphic apparatus on many a holiday tour, when it would be out of all question jif the wet process had to be used. In conclusion, I may say that if only dry plate manu facturers will give the consumer some idea of what he is working with, there will not be half the failures or grumbling and disappointment; and any little extra trouble they may be put to would be amply repaid by the increase of plates got rid of. • B Hictionary of Photogrugh. ACTINOLYTE.—A comprehensive term proposed by Dr. George Wilson, as applicable to substances on which light exerts a chemical and physical change. He says, in lecturing on the theory of photography : “ I have found the word Actinolyte very convenient. ... In its simplest etymological meaning, it signifies a chemical compound analysable into its components by light. I propose, however, to use it in as wide a sense as Faraday’s term, “ electrolyte ” (from which it is borrowed), so as to include chemical synthesis as well as analysis ; and in the present state of our knowledge it would be convenient to extend the term to all the substances employed by photographers on which light exerts a marked, sensible change, although it may be uncertain how far that change is chemical or mechanical.” ACTINOMETER.—!(aarfs, a ray; p.irpov, a measure).—An in- strument for determining the variations of actinic power. The registration of the ever-varying photographic intensity of light is so important a subject, that it has occupied the attention of several eminent scientific observers. It was noticed at a very early period that the chemical activity of the solar rays varied considerably at different hours of the day. Arago, in his address to the French Academy on the discovery of the Daguerreotype process, remarked that there was a great difference in the photographic power of the sun when observed at 10 a.m., and at 2 p.m., in favour of the latter. Further experiments soon showed that there were some alterations in the actinic properties of the light which required further investigation in order to understand it properly; and it became evident that very great advantage would be derived from the construction of some instrument by which these photo graphic variations should be regularly recorded. Mr. Jordan published a paper in the year 1839, on a “ Descrip tion of a New Arrangement of the Heliograph for Registering the Intensity of Solar Light.” In 1840, Sir John Herschell des cribed an “ Actinograph, or Self-Registering Photometer, for Meteorological Purposes.” He says : “ The objects of such an instrumenf, which annot but be one of material importance to the meteorologist, the botanist, and the general physiologist, may be considered as twofold, viz., first, to obtain a permanent, and, at least, self-comparable register, of the momentary amount of general illumination in the visible hemisphere which constitutes daylight; and, secondly, to obtain a similar registry of the intensity, duration, and interruption of the actual sunshine; or, when the sun is not visible, of the illumination of that point in the clouded sky behind which the sun is situated.” Each of these instruments had many points of resemblance. The photographic paper was placed round a cylinder, which was enclosed in another cylinder which was moved on its axis at a certain rate by means of clockwork. A vertical slit, through which the light passed, being made in the outer cylinder, the variations of the light were recorded on that part of the paper opposite which the slit happened to be ; and, by adjusting the rapidity of the movement of the cylinder so as to keep the slit always opposite the sun, the paper recorded every cloud which passed over its disc. Mr. Hunt afterwards constructed an instrument on the same principles as those mentioned above. He says :—“ This actino graph consists of two brass cylinders moving freely upon their axes, one of them containing a powerful clock-spring, by which the apparatus is driven. These cylinders are fixed about twelve inches apart, and around them is placed a band of india-rubber cloth, which, being carried round by friction against the upper working barrel, makes a complete revolution in twenty-four hours. The uniform rate of motion is secured by an ordinary clock escape ment and pendulum. This apparatus is adjusted at such an angle that the direct radiations from a zone of the heavens, about 458 above the visible horizon, may fall upon its upper surface. This clockwork is, therefore, enclosed in a box, and covered with a brass plate, in which there is a triangular opening. The widest part of this opening measures one inch, and the smallest the sixtieth part of an inch. This is divided, 1st, into five holes of such sizes relatively as represent the periods of 1, 2, 3, 4, and 5 minutes; and 2ndly, by bars, the openings between each being adjusted to regularly increasing divisions, from 10 to 60. From this it will be understood that any point of the moving band will be exposed to the daylight for an hour in passing under the largest opening, and the time of exposure diminished by 10 minutes in each of the other divisions until the smaller ones. In these the times of ex posure are, under the largest hole five minutes, and under the smallest one minute. “ If we attach to the moving web a piece of prepared photo graphic paper, it will be evident that for the whole of daylight it will be receiving impressions during the time of exposure above described. The line which passes under the smallest hole will never be exposed for more than a minute, while that which moves under the largest opening will never be exposed for less than an hour; consequently we have the difference between 1 and 60. Now the maximum effect will be the blackening of the paper thoroughly in one minute, when of course the image of the opening and its divisions will be deeply impressed: the minimum effect will be, that the exposure of an hour is necessary to produce any sensible change in the colour of the paper; then we shall have the line under the longest opening alone well defined, the others becoming less and less distinct, until the paper remains absolutely white over those parts which correspond with the diminished openings. It is my intention to fix a numerical value to each of these, which will enable me to tabulate my results, and register the relative value of the actinic radiations by the side of the indi cations of the barometer, thermometer, and hygrometer. I wish to these the photometer could be added, but at present we possess no self-registering instrument which will give us indications of the variations in solar light. “ In the use of this instrument, I prefer presenting it to the light of the northern sky rather than to the direct rays of the sun. In the latter case, every passing cloud which obscured the face of the sun would be registered; but I believe the most accurate registration of the quantity of the chemical radiations active during daylight will be more correctly determined by obtaining constant comparative results from the same point of the northern sky. The material with which I prepare my paper is a standard solution of the oxide of silver in ammonia. One wash only is applied to the paper, which is then found to be sufficiently sensitive for all the purposes of the instrument. “ A solution of that kind, kept in my bottle, remains constant for any length of time. After one single wash of this, the paper is placed damp in the instrument, and exposed during the hours of night; it dries, and in the morning it is in an uniform con dition, which will last during the day.” (To hi continued.)
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