Читать книгу Photography in the Studio and in the Field - Edward M. Estabrooke - Страница 8

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"The discovery that explosive cotton was soluble in ether, was made by Mr. Maynard, who gave it the name of Collodion, and later, in 1848, published in the American Journal of Medical Science the formula for its preparation."

"This ethereal solution, having a certain proportion of alkaline iodides, and iodides of silver added thereto, constituted the collodion first employed by Mr. Archer," who thus shares with Mr. Maynard, and with a Mr. Legray (who first published an account of its use as a photographic agent) the honor of having given to the world the collodion process in photography.

The progress that has been made since Mr. Archer's time in perfecting the adaptability of collodion to photographic uses could not be better illustrated than by comparing the formulæ for collodion first published with those in use at this time.

The practice of photography in the present day by the collodion process is divided into two branches, the positive and the negative.

In the first the object is to obtain in the camera a p15 direct image, which is to be viewed by reflected light, and as it is desired that the pictures so produced should possess pure blacks and whites, certain modifications of the collodion, silver solution and developer are resorted to, which cause these preparations to differ somewhat from those prepared for the production of superior negatives, consequently the formulæ given hereafter will be designated as positive or negative.

These modifications, however, are not of such a character as to render either of the solutions prepared for one process totally unfit to be used for the other, for in fact, many photographers at this day use the same collodion bath and developer for making both positives and negatives.