The photographic news

• Bandzählung: 29.1885
• Erscheinungsdatum: 1885
• Sprache: Englisch
• Signatur: F 135
• Vorlage: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: SLUB Dresden
• Rechtehinweis: Public Domain Mark 1.0
• URN: urn:nbn:de:bsz:14-db-id1780948042-188500006
• PURL: http://digital.slub-dresden.de/id1780948042-18850000
• OAI: oai:de:slub-dresden:db:id-1780948042-18850000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Bemerkung: Seite I-II fehlen in der Vorlage. Paginierfehler: Seite 160 als Seite 144 gezählt.
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

JAXUARY 23, 1885.] THE PHOTOGRAPHIC NEWS. 51 predict half a decade ago, and this makes it ready to believe in the near advent of another change. Is it necessary to mention the numerous occasions upon ■which the doom of albumenized paper has been sounded, as photographic herald after photographic herald has loudly trumpeted forth the merits of process after process. But let us confine our musings to the subject now so pro minently before our readers—the making of prints on the new gelatino brom-chloride paper. Not that it is our in tention to give in this column the formula for suit able emulsion, directions for coating the paper, or details as to development, as all this information will be found in Mr. T. B. B. Wellington’s comprehensive paper of last week (see p. 36), or in other articles which have recently appeared ; but it is rather our purpose to look at the question from such a point of view as the business man is likely to take. If the new printing method is to become a reality for every-day work, certain conditions must be more or less completely satisfied, and if in the case of either one or two of these conditions the balance go against the new paper, there must be very considerable margin of advantage as far as the other points are concerned. 1. The new paper should be obtainable in commerce at a rate not higher than the price of ready-sensitized paper. 2. It must not only be practicable to produce the tone approved of, but it must be possible to do this without any uncertainty, and in the case of negatives varying to some considerable extent in quality and density. 3. The working expenses—that is to say, the salaries of the assistants—must not be considerably more than when ordinary albumenized prints are turned out. 4. The results must be fully equal in appearance to albumen prints, and the mounting must be so done as not to involve any serious difficulty or expense. It is not easy at present to estimate how far the first condition will be fulfilled, although, if one may judge by present prices and processes, it may be conjectured that the cost of the new paper will settle down to a trifle over the cost of sensitive albumenised paper; still, it is neces sary to be guarded in arriving at any conclusion, as im proved methods of working are likely to lead to a con siderable saving in the expense of manufacture, and it may be that in time the paper can be made with less silver in the film than now. The second condition on our list is one which can un doubtedly be satisfied to a very great extent, and perhaps altogether; but as the tone is largely dependent upon not only the proper determination of the exposure, but also on the correct adaptation of the development to the exposure, it is reasonable to expect that greater care and watchfulness will be required on the part of the printer, than when ordinary albumen prints are made. Ihisbrings us to an important point—the salary of the printer ; and experience alone can show whether it will be possible to educate up the present race of printers to the new work without increasing their pay ; indeed, it may be assumed that quite as much skill and judgment is required in working the development method of printing, as in the mere taking of a negative ; and to obtain constantly uni form tones may perhaps demand even more skill than that of an average negative operator. This much is certain : a mere beginner in photography could not be entrusted to take charge of the new printing process; aud an employer might safely reckon on losing something considerable in waste during the instruction of a new worker. As to the mounting and ultimate finishing of the prints, there does not appear to be any difficulty worth mention- iug, as simple hard rolling will bring up a good surface upon the emulsion prints. Warnerke's proposal to squeegee down on thin plates of polished ebonite appears to be an excellent one, while if the prints are gummed on the back while adherent to the ebonite, aud the gum is allowed to dry with the picture, the mounting becomes a very easy matter indeed. It is merely necessary to trim the dry and gummed print; then, after having slightly moistened the mount by means of a sponge, to place the print in position and pass through a rolling press. As one of the older predictions regarding the future of printing by development, the reader may refer to an article contributed by Mr. W. B. Woodbury to the Year- Book for 1865, p. 61, where he will find the importance of using chloride insisted upon. Mr. Woodbury says : “The chloride gives the paper an agreeable tone not to be obtained by the other salts alone.” LENSES FOR PORTRAITURE, BY W. K. BURTON. In a recent editorial article in the Photographic News, which treated of the subject of lenses for portraiture, it was stated that, apertures and focal lengths being equal, the rapidity of a rapid landscape lens would be as great as that of a portrait lens. Mr. W. II. Wheeler points out in your last issue that although this may be true for the centre of the plate, it is not true for the edges ; at any rate, when the landscape lens is used full aperture, the reason being that, in the case of the landscape lens used full aperture, the oblique pencils of light are reduced in intensity by being partly cut off by the mount of the lens, whereas, in the case of the portrait combination—used with the same angular aperture as the landscape lens—the oblique pencils do not inpinge on the lens mount at all. Mr. Wheeler is undoubtedly correct in his argument on this point. The only question to me seems to be whether, by the cause he mentions, any perceptible difference in the rapidity of the two lenses would exist. In the first place, in justice to Mr. W. E. Debenham, let me state that, at the meeting of the Loudon and Pro- yincial Photographic Society to which Mr. Wheeler refers, he (Mr. Debenham) mentioned the very same circum stance that Mr. Wheeler does, as a possible explanation of the fact that a portrait lens may require a less exposure than a rapid landscape lens used with the same angular aperture. Whilst admitting, as explained by Mr. Wheeler, that with a rapid landscape lens the edges of a plate must re ceive less exposure than with a portrait lens used with the same angular aperture, I much doubt if the difference from this cause will make the one lens perceptibly more rapid in practical work than the other. I do not wish to be dog matic on this point; but give the following reasons for the opinion which I hold. /•'irst.—The angle included in portraiture is generally— ought always to be—but a limited one, and the cutting down of the oblique pencils could come into play only to a very small extent, even were the landscape lens used with the full aperture of the lenses, which is very rarely the case, on account of the fixed stop. Second.—-In the case of a portrait negative, we do not judge of the exposure so much by the appearance of the ends and corners as by the portions near the centre. At Mr. Debenham's lecture already referred to, I pointed out a well-known cause which might make a portrait lens somewhat more rapid than a landscape lens used with the same angular aperture. This is, that in the case of the portrait lens, the pencils of light are more condensed by the front combination by the time they reach the dia phragm than in the case of the landscape lens. The difference through this cause is, however, very slight, and is, moreover, almost entirely counteracted by the loss of light iu the portrait combination, through the two extra reflecting surfaces of the lenses. On considering the matter, it appears to me that there is a possible cause for the greater rapidity of the portrait lens which has as yet been overlooked. I put it forward