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. 1283, April 6, 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)
THE PHOTOGRAPHIC NEWS, VoL. XXVII. No. 1283.—April 6, 1883. CONTENTS. Sunpie Drop Shutter 209 The Trimming of Prints 210 New Foreign Lenses 210 Enamelling without Collodion or Gelatine. ByR. Offord ...211 By-the-Bye.—Paris Chit-Chat 211 The English Eclipse Expedition. Bv C. Ray Woods 212 French Correspondence. By Leon Vidal 214 Notes on Celestial Photography. ByR. C. Johnson, F.R.A.S. 215 A New Plate-Carrier 215 Notes 216 Patent Intelligence 218 Twelve Elementary Lessons on Silver Printing 218 PAOE Notes on Photography. By E. Howard Farmer 219 A Method of Toning Gelatine Transparencies. By H. Trueman Wood 220 How to Sensitise Paper. By Henry J. Newton 220 On Gelatino-Chloride Emulsion in the Camera. By A. Cowan 221 To Save Silver Wastes arising from the Development of Plates. ByW. Clement Williams 222 Correspondence 222 Proceedings of Societies.. 222 Talk in the Studio 223 To Correspondents 224 Photographs Registered 224 SIMPLE DROP SHUTTER. It is probable that, in spite of its theoretical defects, the simple drop shutter is at present more used for so-called instantaneous work than all other shutters put together; a few notes on its working will therefore not be out of place, especially as the season for instantaneous work is fast approaching—nay, indeed, has come. We have at various times pointed out that, whatever form of shutter is used, it is most necessary for its efficiency that but a fraction of the total time of exposure should be occupied in the opening and closing of the instrument. This is a statement so apparently self-evident that it would seem only neeessary to make it that it should be acted upon. Yet the vast numbers of shutters in which the instrument is either opening or closing during the whole of the expo sure show that the thing is not thoroughly understood. This is the case in the commonest of all forms of drop shutter, that in which there passes in front or behind the lens an aperture of the same diameter as the lens. In this case, the light received by the plate from the time that the exposure commences till the time that it ends is exactly half what it would be were the lens to be fully open during the whole exposure. As a consequence, one of two things must occur: either the exposure must be doubled in length, giving exactly double the chance of blurring from move ment of the subject, or an amount of light only half as great as might be is allowed to acton the plate, and the effect, probably, is great under-exposure. In either case, the same result is brought about as would occur were a perfect shutter used, and were the area of the stop reduced to one- half, only that the additional flatness of the field and depth of focus which would result from the latter procedure are not brought about. A perfect shutter of any form we need scarcely look for ; in fact, it would appear to be an impossibility. We cannot conceive of any instrument which opens and closes in “ no time.” All that we can do is to make the opening and closing occupy only a fraction of the time of the exposure. In the drop shutter this end is naturally brought about by making the moving aperture long in the direction of its motion. But here at once there appears a disadvantage. The total exposure is made too long. To take an example. Let us suppose the diameter of our lens aperture to be an inch and a-half, and that we make the length of the apeiture of the moving portion of the shutter four inches. There will be exposure during the time that the shutter falls through five and a-half inches, and this will take almost exactly a sixth of a second. This is comparativelv a long exposure—far too long for many subjects. There' is, how ever, a means of readily shortening this, namely, by so con structing our instrument that it will fall for a short dis tance before it opens ; that is, before the exposure com ¬ mences. It is chiefly to point out the advantage to be gained from such a construction that this article is written. To return to our example, suppose that the instrument is so constructed that a drop of only an inch and a-half takes place before exposure commences, we will find that the re maining five and a-half inches are dropped in as nearlv as possiblesecond ; that is to say, by allowing the inch and a-haif of preliminary drop we have at once reduced the length of exposure to one-half what it was before. And let it be noted that not only have we done this, but we have greatly eliminated one of the chief disadvantages of the drop shutter, namely, its property of giving a longer ex posure to the sky than to the foreground. If a drop-shutter is so constructed that the exposure begins whenever the drop commences, the sky receives a much longer exposure than the foreground. The greater the distance which has been fallen before the instrument opens, the more nearly equal will be the exposure of the foreground and the sky. By allowing the dropping piece of a shutter to fall through different distances before the instrument opens, we have a ready method of varying the exposure to a consider able extent. For example, if we allow, in the case which we have imagined, a drop of about four inches to take place before opening commences, we may reduce our exposure to one-third of what it was—namely, to an eighteenth of a second. The alternative method to this one is the fixing of a piece of elastic, either to supplement the action of gravity, or, when the shutter is fixed on its side, to take the place of it. The elastic is a thing to be avoided whenever possible ; it shakes the camera if the tension be anything considerable, and, moreover, the accelerating effect is much less than is generally supposed. The increase of velocity of the moving part is equal only to the square root of the force applied to move it. Thus, returning to our example, let us suppose the dropping part of our shutter to weigh one ounce. The force moving it is gravity, and is equal to an ounce. It might appear that if a force of another ounce was applied by means of elastic, so as to increase the total to two ounces, the exposure would be reduced to one-half; but this is not the case. To reduce the exposure to one-half, we have to bring a force equal to four times the original one to bear. Thus, we would require to apply plus the ounce of gravity in elastic, giving a ten sion of three ounces. To reduce the exposure to one-third, we would require nine times the force, or an elastic tension of eight ounces, plus the one of gravity. This tension— half a pound—is one which would be almost sure to shake the camera. Besides this, if we continue to use our shutter vertically, we retain the difference in exposure given to the foreground and the sky. We have in these remarks been disregarding friction. In the case of the elastic, too, we have been supposing,
- Aktuelle Seite (TXT)
- METS Datei (XML)
- IIIF Manifest (JSON)