Suche löschen...
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
- Strukturtyp
- Band
- Parlamentsperiode
- -
- Wahlperiode
- -
- Bandzählung
- No. 1299, July 27, 1883
- Digitalisat
- SLUB Dresden
- Strukturtyp
- Ausgabe
- Parlamentsperiode
- -
- Wahlperiode
- -
-
Zeitschrift
The photographic news
-
Band
Band
-
- Titelblatt Titelblatt I
- Register Index III
- Ausgabe Ausgabe 1
- Ausgabe Ausgabe 17
- Ausgabe Ausgabe 33
- Ausgabe Ausgabe 49
- Ausgabe Ausgabe 65
- Ausgabe Ausgabe 81
- Ausgabe Ausgabe 97
- Ausgabe Ausgabe 113
- Ausgabe Ausgabe 129
- Ausgabe Ausgabe 145
- Ausgabe Ausgabe 161
- Ausgabe Ausgabe 177
- Ausgabe Ausgabe 193
- Ausgabe Ausgabe 209
- Ausgabe Ausgabe 225
- Ausgabe Ausgabe 241
- Ausgabe Ausgabe 257
- Ausgabe Ausgabe 273
- Ausgabe Ausgabe 289
- Ausgabe Ausgabe 305
- Ausgabe Ausgabe 321
- Ausgabe Ausgabe 337
- Ausgabe Ausgabe 353
- Ausgabe Ausgabe 369
- Ausgabe Ausgabe 385
- Ausgabe Ausgabe 401
- Ausgabe Ausgabe 417
- Ausgabe Ausgabe 433
- Ausgabe Ausgabe 449
- Ausgabe Ausgabe 465
- Ausgabe Ausgabe 481
- Ausgabe Ausgabe 497
- Ausgabe Ausgabe 513
- Ausgabe Ausgabe 529
- Ausgabe Ausgabe 545
- Ausgabe Ausgabe 561
- Ausgabe Ausgabe 577
- Ausgabe Ausgabe 593
- Ausgabe Ausgabe 609
- Ausgabe Ausgabe 625
- Ausgabe Ausgabe 641
- Ausgabe Ausgabe 657
- Ausgabe Ausgabe 673
- Ausgabe Ausgabe 689
- Ausgabe Ausgabe 705
- Ausgabe Ausgabe 721
- Ausgabe Ausgabe 737
- Ausgabe Ausgabe 753
- Ausgabe Ausgabe 769
- Ausgabe Ausgabe 785
- Ausgabe Ausgabe 801
- Ausgabe Ausgabe 817
-
Band
Band
-
- Titel
- The photographic news
- Autor
- Links
- Downloads
- Einzelseite als Bild herunterladen (JPG)
-
Volltext Seite (XML)
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.)
- Aktuelle Seite (TXT)
- METS Datei (XML)
- IIIF Manifest (JSON)