Photography

OXIDE OF SILVER exposed for a few hours to good sunshine, passes into a more decided olive color, than characterises it when first prepared by precipitation from nitrate of silver. Longer exposure renders this color very much lighter, and the covered parts, are found much darker, than those on which the light has acted directly. In some instances where the oxide of silver has been spread on the paper a decided whitening process in some parts, after a few days exposure, is noticed.

At a meeting of the British Association, Professor Grove described a process by which positive calotype pictures could be directly obtained; and thus the necessity to transfer by which the imperfections of the paper are shown, and which is moreover a troublesome and tedious process, is avoided. As light favors most chemical actions, Mr.

A modification of Mr. Talbot's process, to which the name of Chrysotype was given by its discoverer, Sir John Herschel, was communicated in June 1843 to the Royal Society, by that distinguished philosopher. This modification would appear to unite the simplicity of photography with all the distinctness and clearness of calotype. This preparation is as follows.

The several processes enumerated at the head of this chapter, are all discoveries of English philosophers, with the exception of the third and last named. Anthotype was first attempted by M. Ponton a French savan, although it was reserved to Mr. Hunt to bring the process to its present state. The "Crayon Daguerreotype" is an improvement made by J. A Whipple, Esq., of Boston.

So called from the circumstance of cyanogen in its combinations with iron performing a leading part in the process. It was discovered by Sir John Herschel. The process is a simple one, and the resulting pictures are blue.

Under this title a process has been brought forward by Mr. Hunt. It consists of the application of a solution of succinic acid to paper, which is subsequently washed over with nitrate of silver. The image is then to be taken either in the camera or otherwise, as required, and is brought out by the application of the sulphate of iron in solution. Although this process has not come into general use, its exact description may be interesting to the general reader, and we therefore subjoin it.

To any desired quantity of chloride of silver in water add, little by little, cyanide of potassium, shaking well at each addition, until all the cyanide is dissolved. Continue this operation, and add the cyanide, until all the precipitate is taken up and held in solution.

This solution is now ready for the plate-cup. Enough water may be added to cover any sized plate when held perpendicular in the cup. The strength of the solution may be kept up by occasionally adding the chloride of silver and cyanide of potassium. There should alway be a very little excess of the cyanide.

Light--Optics--Solar Spectrum--Decomposition of Light--Light, Heat, and Actinism--Blue Paper and Color for the Walls of the Operating Room--Proportions of Light, Heat, and Actinism composing a Sunbeam--Refraction--Reflection--Lenses--Copying Spherical Aberration--Chromatic Aberration.

The following process possesses some interest, and is worthy a trial from operators. M. Natterer, of Vienna, discovered a process for obtaining proofs on iodized plates with the chloride of sulphur, without the use of mercury.

It is necessary, first of all, to know that you have a chemical which is capable of producing good results when in skillful hands. For this reason it is best to prepare your own quick, after some formula which is known to be good. Those quick-stuffs which contain chloride of iodine are noted for their depth of tone while they probably operate with less uniformity than those which are destitute of it. For operating under ordinary circumstances, especially with an inferior light, probably no accelerator is more quick and sure than Wolcott's.