PHOTOGRAPHIC CORRESPONDENCE.
Lining of Cameras.—I find nothing so good to line a camera with as black velvet; for, black the inside of a camera as you will, if it is hard wood or any size used, there will be reflection from the bottom, which, with very sensitive plates, gives a dulness which, I think I may say, is caused by this reflection. I think even the inside of the lens tube might advantageously be lined with black velvet.
W. M. F.
Cyanuret of Potassium.—I have been using lately 12 grs. of cyanuret of potassium in 1 oz. of water for clearing the collodion plates, instead of hypo. There is one advantage, that there are no crystals formed if imperfectly washed, which is too common with hypo. You must take care to well wash off the developing fluid, whether pyrogallic, protonitrate, or protosulphite: if you use the latter 40-grains strong, the whitest pictures can be obtained, nearly as white as after bichloride of mercury. A good formula to make it is—
| Distilled water | 11 | drachms. |
| Alcohol | 1 | drachm. |
| Nitric acid | 20 | minims. |
| Protosulphate of iron | 60 | grains. |
This I know to act well with care, and it will keep a long time.
I find protonitrate solution—
| Water | 1½ | ounce. |
| Barytes | 150 | grains. |
| Protosulph. | 150 | " |
mixed in a proportion of 8 to 4, with a 3-grain solution of pyrogallic—a very nice developing mixture; and, if poured back again after being used, will suffice 6 or 8 times over; but it is best new.
W. M. F.
Minuteness of Detail on Paper.—Being fond of antiquarian studies, and having learned from "N. & Q." the value of photography to the archæologist, I have serious thoughts of taking up the practice of the art. Before doing so, however, I am anxious to learn how far that minuteness of detail which I so much prize, and which is of such value to the antiquary, is to be obtained by any of the processes on paper. I have seen some specimens produced by collodion which certainly exhibit that quality in an eminent degree. Is anything approaching to such minuteness attainable by any of the Talbotype processes?
F. S. A.
[Had this Query reached us last week, we should then, as now, have replied in the affirmative. We should then have referred, for evidence in support of our statement, to Mr. Fenton's Well Walk, Cheltenham, published in the Photographic Album, and to Mr. Buckle's View of Peterborough. But we may now adduce a work almost more remarkable for this quality, namely, a view of Salisbury, by Mr. Russell Sedgefield, a young wood engraver, which is about to appear in the forthcoming part of the Photographic Album.
To this beautiful specimen of the art we may certainly refer as a proof that it is quite possible to obtain upon paper the greatest nicety of detail; in short, every minuteness that can be desired, or ought to be attempted.]
Stereoscopic Angles.—I think there can be little doubt that Mr. T. L. Merritt (Vol. viii., p. 110.) has solved the problem as to stereoscopic angles: there can be no reason why one angle should be used for near objects, and another for distant. A true representation of nature is required: and, as we cannot view any object with one of our eyes eighteen or twenty feet separate from the other, so it appears to me a true picture cannot be obtained by taking two views so far apart. The result must be to dwarf the objects; and, in confirmation of this, I may state that I was not convinced that the stereoscopic views were taken from nature till I understood the cause of their reduction. All views that I have been able to purchase, of out-door nature, appear to me to be taken from models, and not from the objects themselves.
A view of a tower conveys the idea, not of a tower of stone and lime, but of a very careful model in cardboard; and this is exactly what might be expected from taking the views at so wide an angle. A church is seen, as it would be seen by a giant whose eyes were twenty feet apart, or as we would see a small model of it near at hand.
I hope that some of your photographic correspondents will settle this question, by taking views of the same object both by the wide and close angle, and, by comparing them, ascertain which conveys to the mind the truest representation of nature.
T. B. Johnston.
Edinburgh.
Sisson's developing Solution (Vol. vii., p. 462.).—Will you be so good as to ask Mr. Sisson if he finds the above to answer as a bath to plunge the plate into, instead of pouring on, as in the case of pyrogallic?
He is entitled to the warm thanks of all photographers for the discovery of a solution which produces such pleasing tints with so much ease; and it needs but the qualification I inquire after to render it perfect. I have used it when at least three weeks made, and am not sure that it is not even better than when fresh.
S. B.
P.S.—Why not devote a little more space to this fascinating art in "N. & Q."? I think, if anything, it grows less latterly.
Multiplying Photographs.—In Vol. viii., p. 60., you reprint a communication from Sir W. Herschel which has appeared in The Athenæum.
It describes a method of printing from glass negatives, but there being no cut renders the meaning somewhat obscure.
In the last number of the Photographic Journal (21st ult.), some mention is made of this letter. They say it proves to be one already long in use, Mr. Kilburn having practised it for four years. I am very desirous of obtaining more information about it. I want to know the length of the box or camera required; and also the focus of the lens, and the best size. Probably Mr. Kilburn or Sir W. Herschel would one of them be so kind as to say.
W. M. F.
What kind of lens should be used for taking enlarged copies of glass negatives according to Mr. Stewart's plan? and will the same lens also diminish the picture? Will not the usual camera lens act?
Ply.
[The usual compound lens is all that is required.]
Would you have the goodness to explain, in some detail, the two methods by which Mr. Stewart and Mr. Kilburn multiply photographs in a reduced or magnified size; the one by reflected light, the other by transmitted. Mr. Stewart's experiments are upon glass, Mr. Kilburn's on cameras and daguerreotypes. I have never seen any description of this latter process, or of the method of preparing the stereoscope objects: vide Athenæum, July 30, 1853.
I observe with great pleasure that the cost of apparatus is becoming less, &c.
Amateur.
[However much we may agree in the views expressed in the latter part of An Amateur's letter, we have been obliged to omit it, as it violates our rule of not opening the columns of "N. & Q." to the recommendation of any particular manufacturer.]
Is it dangerous to use the Ammonio-Nitrate of Silver? (Vol. viii., p. 134.).—No: it is now generally used as the best of marking inks, without preparation; and we have never yet heard of an explosion from its use. Mr. Delamotte has evidently confounded this preparation with the chloride of silver precipitated with strong ammonia, which, when dried, forms the article known as fulminating silver; or by adding to the oxide of silver lime-water, and afterwards a strong solution of ammonia, a black powder is thrown down, which, when dried, is known as Berthollet's fulminating silver. There is also one other, formed by adding chloric acid to oxide of silver; after drying this, and then adding potassa to a solution of it, the precipitate, by again being dried, becomes an explosive compound.
The photographer forms a weak solution for his purpose with one of the least soluble and weakest of the ammoniacal preparations, and which, by drying around the stopper of the bottle, is very unlikely to become explosive, from its wanting the addition of another element as necessary to the formation of an explosive compound. For my own part, I must say, that I have found, from experience, all the compound solutions of silver keep much better, and the photogenic effect more satisfactory, by mixing only so much as I may require for immediate use, at this time of the year especially.
J. H.