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
- 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. 1274, February 2, 1883
- Digitalisat
- SLUB Dresden
- Strukturtyp
- Ausgabe
- Parlamentsperiode
- -
- Wahlperiode
- -
-
Zeitschrift
The photographic news
-
Band
Band 27.1883
-
- 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 27.1883
-
- Titel
- The photographic news
- Autor
- Links
- Downloads
- Einzelseite als Bild herunterladen (JPG)
-
Volltext Seite (XML)
tages in gelatine plates over collodion plates, and it is just this one thousand and one matter which must be the coming event. Correspomdemce. THE PHOSPHORESCENT TABLET AS A STANDARD LIGHT. Sib,—As one who has worked with most forms of photometer and sensitometer hitherto proposed, allow me to say a few words regirding the communication of Mr. Arnold Spiller, which appeared in the last number of the NEws. Mr. Spiller’s reasoning appears to be this :—“ One parti cular specimen of phosphorescent sulphide of calcium gave me certain results ; therefore any phosphorescent plate may be used as a standard light, and Warnerke's sensitometer is a reliable instrument." More than a year ago, you pointed out in the Puoro- GRAPHIC News that the difficulties of making a reliable sensitometer are, apart from the question of standard light, very great; but you then indicated a means of obtaining a standard light screen by means of a stepped plate of sulphur. Few commercial products vary so much as the so-called phosphorescent sulphide of calcium. It is rather an oxy sulphide than a true sulphide, and it very often contains free or uncombined sulphur mechanically intermingled with the oxy-sulphide. I have never met with two samples which either gave light of the same colour or the same intensity, and it is my impression that the voilet product generally used for making paint is obtained by mixing various samples, so that the whole is luminous up to a cer tain point; but, notwithstanding this, it varies enormously. The most careful analysis indicates no difference between samples in which the phosphorescence is so feeble as to be of no practical importance, and samples which phosphor esce with violet, blue, green, or yellow light; but a microscopical examination will indicate a distinct difference. Most samples of the violet sulphide which have been examined by myself were found to absorb very much more light at a temperature of about 80* C than at 0°; but when the temperature is considerably increased, say to the melting point of zinc, the reverse holds good, and the colour of the emitted light undergoes a notable change ; but samples vary much in this as in other respects. Many of those who so freely discuss the properties of sul phide of calcium would do well not only to study the fable of the cameleon, but to give full details as to the nature and origin of the sulphide used in their experiments. Calx. grombings of London and Provincial PHOZOGRAPHIC Association. A meeting was held Thursday, January 25, Mr. A. Haddon in the chair. Mr. C. H. Cooke was elected a member of the Association. Mr. Henderson exhibited, on behalf of Mr. Crosby, a nega tive on which, in addition to the subject on which the exposure had been made, a faint but sharply-defined image was found in the centre of the plate after fixing. Mr. Crosby remembered having photographed a similar subject some time ago, and thought that the glass was not properly cleaned. It had been soaked in chromic acid before being used again. Messrs. L. WARNERKE and H. N. King had never had this experience when using dirty glass for gelatine plates, although Mr. King had met with it when using collodion. Mr. W. E. DEBEXHAN attributed the second image to an accidental exposure, or a pinhole photograph caused by a hole in the camera. Mr. Brown showed two plates coated with a fogged emulsion cleared by the use of bromide of potassium ; grain of bromide potassium to each ounce had been added after washing. Mr. W. K. Burton then proceeded to demonstrate his method of preparing gelatine emulsion. He stated that the method was applicable to any formula not containing gelatine in a larger proportion to the silver than 1 to 5. He prepared some emulsion in the presence of the members after the follow ing formula:— A.—Nelson’s gelatine ... 30 grains Potassium bromide 160 ,, Water 10 ounces to be made slightly acid. B. —Nitrate of silver (dry) ... 200 grains C.—Hard gelatine 180 grains To measure, when finished, 10 ounces. He generally used 6 grains of potassium iodide to the above quantity. Solution A is heated to 120° F., when B is added, and the whole well shaken till the silver is dissolved; the colour at this stage is orange or ruby. It is boiled for two hours, and then cooled to 100° F., and three per cent, of ammonia -880 is added. After digesting for two or three hours, it is allowed to settle from twenty-four to forty-eight hours, the supernatant liquid being then poured off and fresh water added, and after standing a second time, the liquid is again poured off. The hard gelatine C, having previously been soaked in water, is now added to the bromide at the bottom of the vessel, and well stirred with a glass rod, warm water being gradually added to dissolve the gelatine, till the whole measures 10 ounces. The ammonia might be omitted if preferred, and boiling for four or five hours substituted. In this case the time of precipitation was extended to a total of five or six days. Some bromide which had been precipitating two or three days was passed round: the supernatant liquid was still slightly orange or ruby in colour, but the emulsion obtained by pouring this oft and adding the gelatine and water to the bromide at the bottom of the beaker was found to be of a blue colour, and some plates coated dried mat in about half-an-hour. He hoped to be able to so modify the process as to get through all the opera tions in two or three hours. The rapidity of the plates varied from 17 to 23 on a Warnerke sensitometer. It was found that if the emulsion was not rapid to start with, it sometimes gained sensitiveness by keeping, but not so if it was already rapid when first prepared ; he always made the gelatine alkaline before using it. He had omitted alcohol, as he had been told, on good autho rity, it might slow the emulsion; precipitation would take place in the presence of alcohol, but was retarded by excess of soluble bromide. If the emulsion, after boiling, was divided, half being washed by decantation, and half mixed with more gelatine and washed in the usual way, that washed by decantation would give the best results. Mr. Henderson said in his experience an emulsion washed by decantation was inferior. Mr. Burton thought there was an advantage in using an excess of soluble bromide in emulsifying, and that by neutralising the excess after boiling with more nitrate of silver, precipitation would take place sooner. Mr. Warnerke said Captain Abney had stated that an excess of bromide gave greater rapidity. In his own experiments he had balanced the quantities of silver and bromide, and then added varying proportions of bromide in excess to separate portion of emulsion, and the results comfirmed Captain Abney’s state ment. Mr. Barker never used a greater excess than two grains to each ten ounces of product, and he never obtained green fog. Mr. Burton thought that when the excess was beyond a certain limit, it made no difference. Mr. Warnerke thought that the slower plates were dried, the greater their sensitiveness. Mr. Henderson said he had added as much as 25 minims of ammonia -880 without causing fog of any sort; the emulsion flowed easily when coating, and there was no frilling. Mr. Warnerke did not think that the state of the weather at the time of preparation had any effect on the emulsion. A good wet plate would register about 10 on the sensitomer. Mr. Warnerke promised at a future meeting to exhibit a new Russian lime light. Photographers’ Benevolent Association. The annual general meeting of this Association was held at 181, Aldersgate Street, on Wednesday, Jan 24th, Mr. W. S. Bird in the chair. The Rev. F. F. Statham was also present. The minutes of the previous meeting were read and confirmed,
- Aktuelle Seite (TXT)
- METS Datei (XML)
- IIIF Manifest (JSON)