. The elements of physiological physics: an outline of the elementary facts, principles, and methods of physics; and their applications in physiology. Biophysics. Chap. THE CAMERA OBSCURA. 375 camera obscura is well known in its form of photo- graphic camera. It consists of a box (Fig. 169), black- ened in the interior to prevent reflection from the walls. In front is a short tube hi containing a system of achromatic lenses. For the back wall of the box is sub- stituted a ground-glass plate g, on which the image formed by the lens is focussed. In photo- graphy, for the ground-glass plat
. The elements of physiological physics: an outline of the elementary facts, principles, and methods of physics; and their applications in physiology. Biophysics. Chap. THE CAMERA OBSCURA. 375 camera obscura is well known in its form of photo- graphic camera. It consists of a box (Fig. 169), black- ened in the interior to prevent reflection from the walls. In front is a short tube hi containing a system of achromatic lenses. For the back wall of the box is sub- stituted a ground-glass plate g, on which the image formed by the lens is focussed. In photo- graphy, for the ground-glass plate a plate sensitive to light is substituted, on which the imaoje ,-1 mi £ v i i Fig. 169.—CameraObscura is thrown. I he action or light on the sensitive surface of the plate produces chemical changes, varying in degree according to the varying intensity of the light in different parts of the image. So that on developing the image by various solutions, the salts of the sensitive coating, that have been acted on by the light, are deposited on the plate. At a point of the image corresponding to a point of the object from which no light was reflected to the camera, no change will have occurred, and that part of the sensitive plate will be removed from the plate. Thus grades of thickness in the plate's coating will be produced, according to the varying lights and shades of the object, and these will constitute the developed image. Besides dark chamber, lens, and sensitive plate, other arrangements are necessary. If the camera be so adapted that parallel rays falling on the lens are brought to a focus on the sensitive plate, it is obvious that divergent rays will not be focussed on. the plate, but behind the plate, so that a blurred instead of a sharp image would result. If, however, the sensitive plate could be moved backwards, it could be made to coincide with the conjugate focus of the rays diverging from the object. This is effected by making the chamber in two halves (b and a
Size: 2019px × 1238px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, bookpublisherphila, bookyear1884
