or Dark Chamber, in Optics, a machine or apparatus representing an artificial eye, by which the images of external objects, received through a double convex glass, are exhibited distinctly, and in their native colours, on a white matter placed within the machine, in the focus of the glass. The first invention of this instrument is ascribed to Baptista Porta.

The camera obscura affords very diverting spectacles; both by exhibiting images perfectly like their objects, each being clothed in its native colours, and by expressing, at the same time, all their motions, which no other art can imitate. By means of this instrument, a person unacquainted with designing will be able to delineate objects with the greatest accuracy and justness, and another well versed in painting will find in it many things to perfect his art.