[The original has not been located. This is from the published version in the Literary Gazette, no. 1277, 10 July 1841, p. 445.]
To the Editor of the Literary Gazette.
Dear Sir, -
The Continental philosophers are frequently making improvements in the Photographic Art, which, it is to be regretted, are little known in England. As some of these are mentioned in a letter <1> which I have received from Dr. Schafhaeutl, <2> dated Munich, June 28th, I communicate to you the following extract. He says: -
"You are, perhaps, aware that Professor Petzval <3> in Vienna, has invented a new combination of achromatic lenses, in order to make the whole aperture useful. <4> Each of the achromatic lenses has an aperture of one and a half inch diameter, and both act together with their full apertures as a single achromatic lens of five and a half inches focus. The diameter of the image in its greatest distinctness is more than four inches. Professor Petzval's first experiments with this instrument were made in the autumn of last year. The plate <5> was prepared with tincture of iodine, according to the process of M. Asherson of Berlin. On a clear day, the person sitting in the shade, never more than two minutes were required to obtain a perfect portrait. The present method of preparing the plate is, however, somewhat different. Iodine is exposed to the vapours of chlorine, and then the watery solution of the resulting brown semi-fluid combination is used instead of the tincture of iodine. Under these circumstances a portrait never requires more than eight or ten seconds, and whole groups of figures obtained in this way make a particularly beautiful effect. According to Professor Von Ettingshausen, <6> the plates become still more sensible when they are first iodised in the usual way, and then held over a feeble solution of chlorine in water till they have assumed a slight reddish tint. Such a plate requires only two seconds in shade, and less than one second in sunshine, but the result is not certain. The brothers Netterer of Vienna made another interesting discovery. They found that a plate treated as usual with iodine, and afterwards exposed in the dark for a short time to the vapours of dichloride of sulphur, received in one minute, in the camera obscura, no perceptible image. But it appeared immediately when the plate was slightly heated, or exposed to the light."
To this extract I would add, that those who take an interest in the subject will find, in the recent numbers of the "Comptes Rendus," <7> several new processes invented by Messrs. Fizeau, <8> Gaudin, <9> and others, the general result of which appears to announce a considerable improvement in the art. I have constructed a camera obscura, in which there are two similar achromatic lenses, the distance between which can be increased or diminished at pleasure. This, I find, gives a very good effect; because it may be so managed as nearly to unite all the chemical rays into one focus. This is the principal thing to be attended to - the achromatism of the lenses with regard to the luminous rays is of no consequence.-
I remain, dear Sir yours, &c.
H. F. Talbot.
31 Sackville Street, <10>
July 5, 1841
1. Not located.
2. Dr Karl Emil von Schafhäutl (1803-1890), photographer, music theorist & geologist.
3. Joseph Petzval (1807-1891), mathematician, inventor and professor of physics at Vienna.
4. This was the first achromatic photographic lens and it was put into production by Voigtlander, a Dutch company producing lenses, the same year.
5. The daguerreotype plate.
6. Probably Andreas von Ettingshausen (1796-1878), Austrian physicist, chemist and photographer.
7. Comptes Rendus hebdomadaires des séances de l' de l'Académie des Sciences.
8. Armand Hippolyte Louis Fizeau (1819-1896), French physicist. In 1841 Fizeau announced his invention of a galvanic process whereby a daguerreotype plate could be turned directly into a printing plate. In November 1843 Antoine Claudet took out the English patent for this process. These prints did not become widespread, but three of them can be found in Nicolas Marie Paymal, Excursions Daguerriennes (Paris: 1842).
9. Marc Antoine Augustin Gaudin (1804-1880), inventor. The above reference is probably to Gaudin's camera obscura, which had the added feature of a variable aperture, in the form of a moveable disc attached to the front of the camera, over the lens. This mechanism anticipated Waterhouse stops by some years. [See Doc. No: 04581].
10. 31 Sackville Street, London residence of the Feildings, often used as a London base by WHFT.