DAGUERREOTYPE APPARATUS

The entire Daguerreotype process is comprised in seven distinct operations; viz:

1.--Cleaning and polishing the plate.

2.--Applying the sensitive coating.

3--Submitting the plate to the action of light in the camera.

4.--Bringing out the picture; in other words rendering it visible.

5.--Fixing the image, or making it permanent--so that the light may no longer act upon it.

6.--Gilding: or covering the picture with a thin film of gold--which not only protects it, but greatly improves its distinctness and tone of color.

7.--Coloring the picture.

For these various operations the following articles--which make up the entire apparatus of a Daguerrean artist--must be procured

1.--THE CAMERA.--(Fig. 5.). The Camera Obscura of the Italian philosophers, although highly appreciated, on account of the magical character of the pictures it produced, remained little other than a scientific toy, until the discovery of M. Daguerre. The value of this instrument is now great, and the interest of the process which it so essentially aids, universally admitted. A full description of it will therefore be interesting.

Fig. 5 (HIPHO_5.jpg)

The camera is a dark box (a), having a tube with lenses (b) placed in one end of it, through which the radiations from external objects pass, and form a diminished picture upon the ground glass (g) placed at the proper distance in the box to receive it; the cap c covering the lenses at b until the plate is ready to receive the image of the object to be copied.

Thus a (fig. 6.) representing the lens, and b the object desired to be represented, the rays (c, c) proceeding from it fall upon the lens, and are transmitted to a point, which varies with the curvature of the glass, where an inverted image (d) of b is very accurately formed. At this point, termed the focus, the sensitive photographic material is placed for the purpose of obtaining the required picture.

Fig. 6 (HIPHO_6.jpg)

The great desideratum in a photographic camera is perfect lenses. They should be achromatic, and the utmost transparency should be obtained; and under the closest inspection of the glass not the slightest wavy appearance, or dark spot should be detected; and a curvature which as much as possible prevents spherical aberration should be secured. The effect produced by this last defect is a convergence of perpendiculars, as for instance; two towers of any building, would be represented as leaning towards each other; and in a portrait the features would seem contracted, distorted and mingled together, so as to throw the picture out of drawing and make it look more like a caricature than a likeness. If the lens be not achromatic, a chromatic aberration takes place, which produces an indistinct, hazy appearance around the edges of the picture, arising from the blending of the rays.

The diameter and focal length of a lens must depend in a great measure on the distance of the object, and also on the superficies of the plate or paper to be covered. For portraits one of 1 1/2 inches diameter, and from 4 1/2 to 5 1/2 inches focus may be used; but for distant views, one from 2 inches to 3 inches diameter, and from 8 to 12 inches focal length will answer much better. For single lenses, the aperture in front should be placed at a distance from it, corresponding to the diameter, and of a size not more than one third of the same. A variety of movable diaphragms or caps, to cover the aperture in front, are very useful, as the intensity of the light may be modified by them and more or less distinctness and clearness of delineation obtained. These caps alway come with Voitlander instruments and should be secured by the purchaser.

Though the single acromatic lens answers very well for copying engravings; taking views from nature or art, for portraits the double should always be used. The extensive manufacture of the most approved cameras, both in Europe and in this country, obviates all necessity for any one attempting to construct one for their own use. Lenses are now made so perfect by some artisans that, what is called the "quick working camera" will take a picture in one second, while the ordinary cameras require from eight to sixty.

The camera in most general use is that manufactured by Voitlander and Son of Germany. Their small size consists of two seperate acromatic lenses; the first, or external one, has a free aperture of 1 1/2 inches; the second, or internal, 1 5/8 inches; and both have the same focus, viz: 5 3/4 inches. The larger size differs from the smaller. The inner lens is an achromatic 3 1/4 inches diameter, its focal length being 30 inches. The outer lens is a meniscus--that is bounded by a concave and convex spherical surface which meet--having a focal length of 18 inches. For every distant view, the aperture in front is contracted by a diaphram to 1/8 of an inch. By this means the light is reflected with considerable intensity and the clearness and correctness of the pictures are truly surprising.

THE AMERICA instruments are constructed on the same principle and many of them are equally perfect. Mr. Edward Anthony of 205 Broadway, New York city, has constructed, and sold cameras fully equal to the German and for which Voitlander instruments have been refused in exchange by the purchaser.