tabletop illuminator. Because the transparent mirror (fig. IB) re- 

 verses images in reflection, the transparency is reversed when 

 mounted on the opal plexiglas easel (fig. 1C) so that the image is 

 viewed through the emulsion side rather than the base side of the 

 film . This makes it possible to view the reflected photographic 

 image in its correct orientation without impairing its quality. 

 Figure 2, a functional diagram of the device, omits the Old Delft 

 stereoscope in order to show other details more clearly. The dashed 

 lines indicate the optical path through the stereoscope from eye- 

 piece to transparencies. 



Setting up the Old Delft device for use is relatively simple and 

 can be accomplished in the following steps: 



1. The new photography — a stereo-pair — to which a plot is to 

 be transferred is mounted and oriented on the tabletop illuminator 

 for normal viewing with the stereoscope. 



2. The original transparency, on which the plot is located, is 

 mounted on the upright easel with the emulsion side out (fig. 1C). 



3. The easel is placed to the right of, and in line with, the 

 transparencies mounted on the illuminator. 



4. While looking through the stereoscope, the transparent mirror 

 is swung into position in the optical path of the right eye. (The 

 stereoscope can be moved to the left or right so as to utilize a 

 maximum area of the mirror without destroying the orientation of 

 the transparencies already alined on the illuminator.) 



5. The illuminator behind the easel is turned on by depressing 

 the foot switch (fig. ID), thereby superimposing the details of the 

 plot on the stereo-model under the stereoscope. The transferred 

 plot will always be marked on the left-hand transparency of the 

 stereo-pair, due to the position of the transparent mirror. (By 

 reducing the amount of light under the right-hand transparency of 

 the stereo-pair, the plot image on the original transparency will 

 appear brighter, permitting better orientation with the plot image 

 on the left-hand transparency.) 



6. The superimposed images can be adjusted to the new 

 transparencies by moving the easel in any of the four possible axes 



