![]() represents the two perspective projections of a cube b is that seen by the right eye, and a that presented to the left eye the figure being supposed to be placed about seven inches immediately before the spectator. This fact may be easily verified by placing any figure of three dimensions, an outline cube for instance, at a moderate distance before the eyes, and while the head is kept perfectly steady, viewing it with each eye successively while the other is closed. But this similarity no longer exists when the object is placed so near the eyes that to view it the optic axes must converge under these conditions a different perspective projection of it is seen by each eye, and these perspectives are more dissimilar as the convergence of the optic axes becomes greater. There is, in such case, no difference between the visual appearance of an object in relief and its perspective projection on a plane surface and hence pictorial representations of distant objects, when those circumstances which would prevent or disturb the illusion are carefully excluded, may be rendered such perfect resemblances of the objects they are intended to represent as to be mistaken for them the Diorama is an instance of this. When an object is viewed at so great a distance that the optic axes of both eyes are sensibly parallel when directed towards it, the perspective projections of it, seen by each eye separately, are similar, and the appearance to the two eyes is precisely the same as when the object is seen by one eye only.
0 Comments
Leave a Reply. |