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The photographic news
- Bandzählung
- 6.1862
- Erscheinungsdatum
- 1862
- Sprache
- Englisch
- Signatur
- F 135
- Vorlage
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- Hochschule für Grafik und Buchkunst Leipzig
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- SLUB Dresden
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- urn:nbn:de:bsz:14-db-id1780948042-186200003
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- http://digital.slub-dresden.de/id1780948042-18620000
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- oai:de:slub-dresden:db:id-1780948042-18620000
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- Seite 1-72 fehlen in der Vorlage. Vorlagebedingter Textverlust.
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- Parlamentsperiode
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- Wahlperiode
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- Bandzählung
- No. 208, August 29, 1862
- Digitalisat
- SLUB Dresden
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- Ausgabe
- Parlamentsperiode
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- Wahlperiode
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Zeitschrift
The photographic news
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Band
Band 6.1862
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- Ausgabe Ausgabe 73
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- Ausgabe Ausgabe 589
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- Register Index 619
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Band
Band 6.1862
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- Titel
- The photographic news
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i aad ed ' ,, equirad ■01» ,b "whe velopd iedexf The ny vd ina dr) . This ;t state; n prir ver, bu follot mersed to flos‘ 5 usudl ed by s closing netrate not the a gl s iven by a long i albt- ler th-' ions i* s ma lie. refully omen’ out of 1 with t than >g ' K the atly show the importance of my remarks on paper. I would just add in conclusion, the greatest care should be exercised by paper albumenizers, in order to secure a perfectly even sur face on the papers used; and if a material of coarse texture is used, let it be made use of in a plainly salted condition. I shall next week (with your permission), have a few remarks to make on the silver bath.—I remain, yours respectfully, A Photo’s Assistant. P.S.—An error, which doubtless was my own (as I have to write in haste), appeared in my last letter; speaking of ‘ toning after printing by diffused light,’ it should read, ‘ a mere alkaline reaction is all that is required.’ Aqotographi Zlotes anir (Queries. FREE Nitrate in Toned Prints. Sis,—In a recent number of the British Journal, in an article on Toning, George Dawson, Lecturer on Photography, at King’s College, in speaking of the first washing, says :— “ The importance of thorough washing cannot bo too strongly insisted on, not merely because it facilitates the toning, and prevents mealiness, but because, in the after fixing bath, free nitrate of silver is certain to generate sulphuric acid, to the per manent detriment of the pictures.” Now, though I perfectly agree with Mr. Dawson as to the importance of thorough washing, I think you will agree with me, Mr. Editor, that his chemistry is quite at fault, when ho gives as a reason that “ free nitrate of silver is certain to gene rate SO, in the after fixing bath,” for I cannot perceive how any free nitrate of silver can pass through the toning bath of chloride of gold and acetate of soda without being decomposed ; and if it bo decomposed, how can it be present so as to generate sulphuric acid in the hyposulphite bath?—Your obedient ser vant, W. W. Bristol, August ith, 1862. [Eroe nitrate of silver would be decomposed in the toning, even without excess of alkali, and unless a very large excess of silver were present, it would not be likely to reach the hypo in the form of a nitrate. The sentence has probably been written thoughtlessly, for we believe Mr. Dawson is a good chemist.—Ed.] Angle included by View Lenses. Sib,—In your note to my letter “ On the Angle included by View Lenses ” in the last number of your Journal, you say that “ to test the lenses properly it would be necessary to use a triple of an equivalent focus, the same length as that of the single lens, to try each lens with the same sized stop, and to use a plate larger than they were intended to cover.” You must allow me to say that I consider these conditions to be by no means neces sary. In my experiments I did use the same sized stops, and I found that both lenses being of precisely the same focus as measured from the back lens of the triplet, the single lens included about one-seventh more subject on the same surface of glass than the triplet, consequently the angle was so much larger in the former. My subsequent observation was to the effect that it was un fair to measure the focus from the back lens of a combination, but that the equivalent should, in all cases, bo given. Such equivalent will include, I believe, precisely the same angle as that included by a single lens of the same focus and no more.— I am, sir, yours very respectfully, BAYNIIAat Jones. Cheltenham, “Both August, 1862. [On a little reflection you will see that your experiment is entirely fallacious. You used a single lens of shorter focus than the triple ; and, therefore, from the same point and on the same sized plate necessarily included more subject with the short focus than with the long one. But no argument of any kind is thence desirable as to the respective capacities of the two lenses as to angle of view. It is unquestionably a very erroneous plan to state the focus of any compound lens as measured from the back glass. But, notwithstanding that you condemn the practice, you follow it in making your experiment. We repeat it that to make the results fairly comparable, lenses of similar equivalent focus should bo used, and that it is desirable to work on glasses larger than the lenses are intended to cover, to facili tate examination of tho exact extent of satisfactory definition in each.—Ed.] August 29,1862.] THE PHOTOGRAPHIC NEWS. The plate being washed, a little pure solution of pyrogallic Siis poured over it, drained off, and again poured on, first siding a few drops of a solution of nitrate of silver of 3 per W. The picture is fixed with hyposulphite of soda. PRINTING AND TONING DIFFICULTIES. Sin,—Entertaining an utter aversion to all secret dodges, Which only tend to retard the healthful growth and progress । our fascinating art, I willingly respond to your invitation zfreely devoting a few of my limited moments of leisure to •further consideration of the subject on which I treated some- Ptat briefly in your last number ; and as I purpose entering Ily into the various windings of that apparently intricate "hitherto perplexing subject, I shall endeavour to sim- jifyand arrange the various causes which produce the evils ’He spoken of. In order that I may accomplish this self- "posed task more effectually, it will be necessary for me to Cueuss the subject of printing and toning by pausing to Hte a few remarks as I enter upon each of the several "Bes pertaining to those interesting processes, avoiding un- Pessary prolixity. I shall advance many arguments which te a tendency to support the new theory of surface im- Miments, I have launched into the photographic world, Ad if, by my humble efforts, one stone is added to the We and fast growing structure of photographic art, my wars will be more than amply repaid. Commencing with paper. Oh, what a mass of learned "Buments has been advanced on this topic 1 but still biographers despairingly cry, “When and where shall find a paper vendor honest enough to deliver us from “"•rapidly growing evil?” A great difference, I will Mnit, exists in the various papers now in the market, and । °'m as albumenized papers, some samples of which are tally unfitted for photographic purposes ; this may be A'buted to an ignorance of the conditions required, rather ? 3a to any feelings of dishonesty on the part of the “ers; to remove this ignorance, I will now proceed to ^the views I entertain on this subject. The texture of paper employed in printing should be as fine Y «ven as it is possible for art to make it, in order that the glances employed in the production of the picture may 1 stained without a flaw upon its surface; the more per- 1 "tly this can be accomplished, the more perfect will be the int produced, for a coarse absorptive texture is not only % most prone to mealiness, but I have known it to cause Htortion in the image, when by long soaking the pores distended, and, whilst drying, have twisted themselves a different position. The importance of the above "arks will be more clearly shown in the following hints Ealbumenizing. When a thin solution of albumen is ?•> on which to float paper of coarse and irregular texture, 0 quantity of that substance which remains on the surface 1 Ihe paper, when dry, will be very uneven, the most ab- oyent parts contain the thickest layer of albumen, and enSeguently a larger share of the chloride used, and when 8 tized it will evidently contain a double share of silver ; I,n-ast, after reduction by light, when placed in the toning o il will act as an impediment, which will mar the beauty M; he print, because the adjacent portions of the paper, visEh contain less silver, will be thoroughly toned ere any 4 dble effect has been produced on the parts which contain nioble portion of silver and albumen, hence the cause of fonPots, known as uneven toning ; proof of this may be »l|, in the fact, that, be a paper ever so good, if a wave of Lhonen should be allowed to accumulate near its edges, leu. Postions of the paper will appear the colour of red it th; ttis red appearance is but the results of contrast, for Pieti Portion be separated from the perfect parts of the Parti, it will be readily perceived that it has undergone a hhay 1 change from the effects of toning. Another proof laper 6 advanced, in the fact of an highly albumenized Vqlvrguiring a much longer time to tone than a more • coated sample ; but I bel icve I have said sufficient to 419
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