Optics of photography : on a new process for equalizing the definition of all the planes of a solid figure represented in a photographic picture / by A. Claudet.

  • Claudet, A. (Antoine), 1797-1867.
Date:
[1866?]
Catalogue details

Licence: Public Domain Mark

Credit: Optics of photography : on a new process for equalizing the definition of all the planes of a solid figure represented in a photographic picture / by A. Claudet. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    altered the focus, the image of the eyes, and finally, after again altering the focus, the image of the ear, and then, from these various images, forming a collective portrait. Such an idea may appear impracticable, possibly even absurd, and it is sure on first thoughts to be rejected and condemned. Yet I seriously, and after mature consideration both of the practice and of the theoi’y of such a scheme, propose its adoption as one of the greatest im- provements which will have been introduced in photography since irs discovery. I beg to be allowed to explain the method in which T conceive I have solved the difficulty I have above al- luded to. Let me premise a few words upon the effect produced by the ex- periment of taking the photographic image off the focimeter. This instrument, I may be permitted to remark, was invented by me upwards of twenty years ago, and has been constantly used in my operating-room in order to test in what degree the chemical and visual foci of lenses coincided or differed. Until it came into use, nobody had ever dreamt that they did not exist in the same plane when the object-glasses were as much achromatic as those of the best telescopes. This fact being demonstrated by the instru- ment I refer to, was the cause of a complete change in the con- struction of lenses for photographic purposes; and from that time opticians have endeavoured to calculate, and succeeded in disco- vering curvatures the combination of which, to invent a phrase, achromatize, with the visible rays of light, the invisible rays which are exclusively endowed with the chemical action. The use of the focimeter I have found indispensable since the further discovery I have made that the two foci undei’go continual changes from various atmospheric influences; and no photographic studio, therefore, should be without this instrument; for no optical combination is capable of preserving an invariable coincidence of foci, and the photographer must have the means at any moment of testing the then state of the elements, and of the light itself, in order to ascertain any change in its refraction and to act ac- cordingly. My focimeter, a model of which is on the table, is made of eight separate segments of a disk, mounted spirally on a hori- zontal axis of 12 inches, corresponding with the optical axis of the lens; the segments are all separated and distant about inch from each other. In a front view they form on the ground glass the image of a complete and regular disk. The segments are covered with some uniform and well-defined devices; and the centre of each is mai’ked with its number, from 1 to 8. The first segment is the nearest, and the last the furthest from the lens. , 13y moving slightly and slowly forward and backward the lo-