STEREOSCOPY WITH ONE LENS, ONE EXPOSURE.
The inventor of the last mentioned device was also the originator of the instrument termed the " Stereoscopic Transmitter," shown in the accompanying illustration, Fig. 827. Here the principle of reflection is used in the following manner, reference being made to Fig. 828. Let an ordinary camera with only one lens be represented at it, the transmitter at c D, and the subject to be photo graphed at A B. In virtue of the fact that the angle of reflection is equal to the angle of incidence, light emanating from A B will be reflected by the mirror c, through the lens to the portion of the plate F, whilst light coming from the same source A B and received on the mirror D will be reflected through the lens to the portion of the plate at E. A person standing at A B, and looking to wards c and D, would see a double reflec tion of the single camera H at 0, the latter representing, and, indeed, acting the part of, a twin lens camera. Hence the sub ject being reflected from two separate view points, i.e. c and D, dissimilar images will be received upon the two halves of the plate E and F in the camera H, such images being stereoscopic phases. A
point in favour of this system is that, during the process of reflection, the light from the separate view points is made to cross before reaching the sensitive plate, so that transposition of the images takes place irrespective of inversion—a fact which enables prints to be made direct from the negative so obtained, when they will be found in their proper order for immediate mounting and inspection in the stereoscope. Against this advantage, however, must be set the fact that as the dissimilar images are reflected, they be come reversed as regards right and left, an error which may easily be corrected by the carbon or other similar process if it is imperative that the subject should be correctly shown in this respect. It is also suggested that when using films they may be inserted in the camera, celluloid surface uppermost, so that the picture reaches the sensitive film after passing through the celluloid, a process that would correct inversion in the printing stage.