object at 50 m from the lens and A to be 1 m, this ratio is 50/1. And further if 
we assume that 5 mm is appropriate for the breadth of Si', the breadth of Si has 
to be 1/10 mm. Now let us limit the aperture of the lens L y with a slit of 5mm 
breadth. The beam projected by the lens L y is perfectly plane one of 5mm thick 
ness to the deepest point of the object, and diverges from there on as shown in 
Fig. 3. Utilizing this fact, we need not adjust A for every contour, provided that 
B is taken sufficiently large. We have only to adjust the initial directions of the 
beams and the shifting speed of the slits at every start of scanning. 
As those that have been mentioned seem to be practicable if the mechanism 
of adjustment is made with high accuracy, it is thought to be not very difficult 
to make the ortho-contour photography applicable for such a scale of object as a 
building. 
On the other hand, this method seems to be useful for objects of very small 
scale. If an object under a microscope has an uneven surface, the microphoto 
graph taken is only sharp on one contour and other parts are less useful. A 
series of contours of sharp image taken by this method will express the real as 
pect of the object more explicitly. Such a photograph is, of course, useful as a 
photogrammetric record, and besides, it will give the best appearance of the whole 
object.