Figure 4 shows how the device works. Looking through the 

 stereoscope, the interpreter alines the image of the new trans- 

 parency, mounted on the illuminator under the left-hand mirror 

 system, with the image of the original transparency, mounted on 

 the upright easel. As shown in the diagram, the original is mounted 

 with the base side out . This is because the Amici prism bends light 

 rays 90° and erects the image, instead of reversing the image like a 

 mirror. The prism effect allows the device to be used with opaque 

 prints, either color or black and white, and may make it suitable 

 for other phototransfer work. 



Adjusting the position of the photograph on the tabletop illumina- 

 tor or the position of the easel will allow orientation of images 

 within any portion of the area common to both photographs. Scale, 

 tip, tilt, and swing can be adjusted by moving the easel in any of the 

 four axes. The plot corners are transferred as described for the 

 Old Delft device. 



Using this equipment with color transparencies, 200 plots were 

 transferred in a 5-day period. Unlike the Old Delft device, however, 

 the new plot locations had to be interpreted as a separate operation. 

 Thus, interpreting at a rate of 60 plots per day, 8f days were re- 

 quired to do the work that was done in 5 days with the Old Delft 

 device. 



These two devices can be made in any shop equipped with the 

 common types of metal-working tools. The materials are obtainable 

 from sheet metal, electrical, and optical supply outlets at nominal 

 cost. Drawings and material lists can be obtained on request from 

 the Forest Insect Laboratory, Agricultural Research Center, 

 Beltsville, Md. 



