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The photographic news
- Bandzählung
- 35.1891
- Erscheinungsdatum
- 1891
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- Englisch
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- Hochschule für Grafik und Buchkunst Leipzig
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- Hochschule für Grafik und Buchkunst Leipzig
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- Bandzählung
- No. 1692, February 6, 1891
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Zeitschrift
The photographic news
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Band 35.1891
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FEBRUARY 6, 1891.] THE PHOTOGRAPHIC NEWS. 105 RESULTS OBTAINED WITH THE AMYL ACETATE LAMP.* BY DR. J. M. EDER, Director of the Imperial School for Photography and Repro duction Processes, in Vienna. As is well-known, the International Photographic Con gress in Paris adopted the amyl-acetate lamp as a prac tical standard of light, and this standard is certain and easy to apply. For a knowledge of the light-sensitiveness of various photographic preparations, a comparison with the amyl acetate lamp is desirable. [ For this purpose a reduction to the so-called meter- candle is necessary. If the amyl-acetate lamp is taken as a unit, the amount of light falling vertically upon a sur face placed at a distance of cne meter is called a meter- candle (meter-kerze). The amount of light necessary to produce a visible action upon a bromide of silver gelatine plate can be accurately expressed in figures. According to Dr. Michalke, with oxalate developer a visible impres sion is produced on a bromide of silver gelatine plate when the latter is subjected during one second to the action of a volume of light equal to 0’045 of a meter- candle. Making use of the table of sensitiveness of various photographic preparations, prepared by me, the following table is obtained. The latter gives the volume of light, expressed in meter-candles, which must act during one second to produce a visible effect. TABLE. —Amount of light, expressed in meter-candles, which must act dur ing one second in order to produce a photo-chemical effect. ... Volume of light in Light-sensitive preparation. meter-candle, acting , . during one second. 1. Bromide ot silver gelatine plate with oxalate developer, sensitiveness = 23° Warnerke 0-05 2, Bromide of silver gelatine plate with oxalate developer, less sensitive = 18-19° Warnerke 0-15-0-20 3. Wet collodion plate 1’8 (average 2) 4. Daguerreotype plate 27-90 5. Collodion dry plate, with alkaline developer, tannin, &c. 9-14’4 6. Chloride of silver gelatine plate with oxalate developer (Eder) 14-0 7. Pigment paper 1440-5400 8. Silvered albumen paper, direct copying ... 4500-18000 This table has, of course, only an approximate value. It gives, however, a very good summary of the necessary exposure required by the various methods. Expressing the sensitiveness of photographic preparations according to the effect of a meter-candle during a second’s expo sure, has this particular advantage, that it gives at once the relative exposure required by the photographic methods in question. It must further be mentioned that only the first six photographic preparations in the table could be tested directly with the amyl-acetate lamp, not the two last copying processes, which are not in the least sensitive to the light of a candle or amyl-acetate lamp. In order to be able to take account of pigment processes and silvered paper in this table, their sensitiveness with daylight was used, c.g., pigment paper is in daylight 800 to 3,000 times less sensitive than a wet collodion plate with ferrous- *" Photographic Mosaics. The original title is " Photometrical Determination of the Amount of Light necessary to Produce an Impres- slon with Various Photographic Preparations.” oxalate developer. Since this last requires 1’8 meter- candles for a visible impression, then the volume of light necessary for the production of a picture with pigment paper would be 1’8 X 800 to 1’8 X 3,000, or 1,440 to 5,400 candle-meters. With orthochromatic plates and the amyl-acetate lamp the light-sensitiveness appears (compared with ordinary bromide plates) proportionately higher, which is evidently the result of the different spectral composition of day light and the flame of the amyl-acetate lamp, since in the latter there are relatively many more orange-red, yellow, and green rays than there are blue and violet. London and Provincial Photographic Association.—The next meeting, on February 12th, at the “ Champion Hotel,” Aldersgate Street, will be a lantern evening, when visitors are invited. Royal Institution of Great Britain.—At the general monthly meeting on Monday, February 2nd, Lady Abel, Mr. John Aird, M.P., Mr. Henry Graham Harris, M. Inst. C.E., Mr. Sydney Turner Klein, F.L.S., F.R.H.S., were elected members of the Royal Institution. Amateur and Professional.—A correspondent sends the subjoined cutting from The Cape Register, Exchange, andBartcrot January 3rd:—“Photography—‘Prefer loss to an unjust gain.’ This, readers, is a very old proverb, but nevertheless the advice it gives holds good. Our readers may wonder what we are alluding to. As it is the duty of every free and independent newspaper to expose meanness in all its various aspects, we unhesitatingly call attention to the fact that the various photographers of this town—professional men who have undergone, in many instances, a long course of study to master the art, gentlemen who are paying high rents and heavy taxes —are deliberately and coolly swindled by so-called amateur photographers who on week days and Sundays roam about the country with their photographic apparatuses, and cheat the professional men out of their just dues. We do not by any means allude to those real amateur photographers who take a pride in the art, and practise for art’s sake alone, and not for gain, but we refer to those persons (we might use a stronger name) who, with their photographic instruments and appen dages, prowl in the vicinity of picnic parties, gentlemen’s houses, and other places of interest, and without invitation proceed to take a likeness (as a rule it is the greatest daub imaginable), and when spoken to they invariably answer that they are simply amateur photographers, and will be glad to send a gratis copy, when finished, to the leader of the picnics alluded to, or the proprietor of the estate they have encroached upon ; but they further hint that if an order is given for, say, one or two dozen copies, they will be compelled to charge just a little (?) to cover expenses. As a rule the bait is readily swallowed, the money paid in advance, and the order given. When the photos arrive at their destination—and sometimes they do not—the innocents see that they have copies of a very inferior description. But what can the victims of this duplicity do in the matter ? Why, simply grin and bear it. A few days ago one of the fraternity coolly came up to a house in the Gardens and commenced operations. He took the house, he took the children, he took the dogs, and, in fact, he would have taken anything presentable. In this instance he was doomed to disappointment, and sternly told to clear out betore he was able to complete his peregrinations, and he marched off with a sulky and disappointed air. This is one of many instances, and we are of opinion that the legitimate photographers of this and other towns should resent the con duct of these individuals in a proper manner, and no doubt the public would assist in the matter. We have penned these lines simply to expose what we consider a gross fraud, and we further hope they may be the means of calling attention to this glaring evil and unfair proceeding on the part of those who try to increase their living in an unmanly and surrep titious manner, and who should be made to pay the penalty of their pernicious conduct, and then they will all be ‘ Must commc unpoisson.’ ”
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