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APRIL 24, 1885.] THE PHOTOGRAPHIC NEWS 261 way so far as Messra, Braun and Co.’s establishment at Dirnach, in order to have the pictures in our National collection properly photographed. It is probable that both these reasons influenced the decision, for a discussion took place; albeit, no new points fell from the speakers who were engaged therein, and the author, in that portion of his paper which dealt with the cosmopolitan nature of art. gave certain reasons tending to justify the selection. Those who had the opportunity of examining some of the examples with which the paper was illustrated, were by no means agreed as to how far the results were due to skilful retouching beyond the legitimate limit, and how far to chemical and other means ; neither were they assisted in their deliberations by any information as to Messrs. Braun’s modus operandi, beyond a claim by the said firm that their process of reproducing paintings was a secret one, and better than any one else’s. It is pretty generally understood by English copyists how to photograph a painting; some manipulators prefer to make the negative in direct light, at the same time carefully providing against all possible reflection from the surface of the painting, beyond that which is necessary to obtain an image; others give preference to an equally diffused light, such as may be obtained in the open air. Sunlight, too, has its adherents. Then, again, we find that many successful results are obtained by the use of the reversing mirror. Whicheve of these methods of illumi nating be adopted, it is usual to make a preliminary nega tive somewhat smaller than the original, and for this pur pose the gelatino-bromide process is, for several reasons, peculiarly suited. Butting aside for the moment the gain in rapidity, and the absence of many defects met with in the wet cododion process, we find that bromide of silver in gelatine tends to the direction of rendering detail not easily obtained with collodion containing a large proportion of one or more iodides ; this result, added to the more har monious rendering of the strong lights, enables the photo grapher to make a negative in which he has a truer repre sentation of the painting, and one in which harshness, cracks, and fissures are less obtrusive. Upon a preliminary negative of tnis kind, a considerable amount of modification can be worked, both sides being utilizable for this purpose ; here it is that the method mentioned by Mr. W. England, in the discussion referred to, proves of especial value, always provided the truth is not sacrificed. Another power of no less magnitude is the skilful manipu lation of a transparency from this dodged preliminary negative. Such a transparent positive may be either from collodion, gelatino-bromide, chloride, or carbon tissue, the two former processes allowing for enlargement; the latter not so. As a rule, the first or last named is generally pre ferred ; in skilled hands such positives are amenable to an immense amount of alteration, and frequently of improve ment, the final negative, which is usually by the wet collodion process, requiring nothing beyond the merest touches for the removal of ordinary defects. There are other methods of producing photographic copies of paint ings, wherein the artist’s brush is more or less brought into requisition. These methods are doubtless familiar to all practical photographers, and need not be dwelt upon now, since sufficient has already been mentioned to illus trate the value of mechanical contrivances artistically pur sued. That certain modifications of the sensitive film assists us towards successfully photographing colours, in accordance with their true value as regards lumin osity, is a f.ct which has been proved beyond question. Sir J. Herschel’s and Mr. 11. Hunt’s experiments in this direction were valuable, but they have only been considered practical since the researches of Major-Gene ral Waterhouse, l)rs. Vogel, Lohse, Captain Abney, Mr. E. E. Ives, and others, have been recorded. It will be remembered that the particular influence exerted —and it is a marked one—in the recent experiments is effected by staining the sensitive film with a substance which exalts the sensitiveness of the rays of lower refrangibility, without increasing the blue and the violet materially, in some cases, and decreasing their energy in others. Working upon the same lines as the earlier experimenters—namely, photographing through coloured mediums—it is found that the refrangibility of blue and violet rays can be greatly lowered in this way without exercising any corresponding disadvantage upon the yellows, greens, and reds. Thus, if we photograph two bands of colours —say, one of them yellow, and the other blue—under ordinary circumstances, with wet collodion, we should obtain a dark hand in the first instance, and a light band in the second ; but if we had repeated the operation, having first taken the precaution to stain the film, and interpose a suitable medium between the object and the objective, a totally different result would have been obtained—the luminosity of the yellow would have asserted its supremacy. Captain Abney’s “ canary stained glass ” forms a suitable medium for the purpose ; but it must be borne in mind that the interposition of this medium necessitates a prolonged exposure. Among the recent experiments published by Dr. Vogel, we find that in addition to interposing a medium similar to the above, he obtains the most decided advantages by incorporating eosine with his sensitive film; the results were exhibited before the German Societies, and much appreciated. The treatment of collodio-bromide plates with chlorophyll recommended for a similar purpose by Mr. F. E. Ives, an illustration of the capabilities of which is published in the current Year-Book, shows conclusively how much can be done by chemical means alone. Another familiar substance, recommended by Dr. Lohse, “ Turmeric,” has special qualities which recommend its employment, not the least advantage being that it may be used without an interposing medium or extra trouble beyond soaking a gelatino-bromide plate for the space of a. few minutes in an alcoholic extract of turmeric root im mediately before exposure. It does not appreciably in crease the exposure, and much of the colour leaves the film during fixing. Doubtless many plants would yield alcoholic extracts presenting similar qualities if the subject were investigated in the manner its importance deserves. 1 have before me two negatives representing twenty-six squares of coloured ribbons, mounted to form five distinct bands, containing in the aggregate all the colours ordinarily met with by the photographer. Thus, in the first band we start with pale buff, and terminate with a deep and rich orange; and in like manner bands containing varied shades of red,blue, and green are made up. These negatives, together with the tablet of mounted ribbons, was sent to me by Mr. Offord nearly a year ago ; one of the negatives having been exposed on the tablet in the ordinary way, and the other had been previously soaked, as recommended by Dr. Lohse, in a solution of turmeric. The difference between these two negatives was so remarkable that I con sidered the matter of sufficient importance to repeat the experiment with the view to its mention at the photo graphic societies. My results being similar, led me to try other substances, among them being an alcoholic extract of the petals of the French marigold, which exercised a similar, though more marked influence, than the turmeric ; but like Mr. F. E. Ives’ chlorophyll, its value depends very much on its freshness. Upon the occasion of mentioning these experiments at the August technical meeting of the Photographic Society of Great Britain, I advocated the formation of a committee whose duty it should be to make a series of comparative experiments with the substances already published, as well as with the isochromatic plates of foreign manufacture. So far as known to me, no such series of experimeuts have yet been officially carried out, therefore I heartily second the Hon. Treasurer’s request that the Parent Society of photo graphers shall give this subject their attention,