JULIUS RHEINBERG ON STEREOSCOPIC EFFECT AND A 



had the magnification been J (l only, it would have served to 

 penetrate 2 mm. It is seen, therefore, that whilst with very 

 low powers tin' eye accommodation plays a very considerable 

 j,;, : t. aa we go to higher powers its scope becomes more and 

 more limited; and when we add the eye accommodation to the 

 I tli we get from the objective, so as to get the total 

 penetrating power, the same thing holds good. 



We can best form aii idea of this by comparing the amount of 

 ion with the size of the field of view, and it is found 

 that when we employ a moderate magnification, such as 100, the 

 power to penetrate may amount to about T ^yth of the diameter 

 of the field of view; if the magnification is 1,000, we cannot 

 penetrate to more than T o\joth of it. 



Abbe also points out that the same causes which operate to 



>ming disadvantage in so greatly reducing the possibility of 

 penetration when we increase the magnification have, however, 

 a compensating advantage ; for they serve to make the layers 

 which are in focus stand out more distinctly from the others, so 

 that, by adjusting for successive planes, we can accurately 

 construe the form of the object, and form our ideas as to space 

 relations with a like degree of certainty. This is an advantage 

 which does not come into play with the unaided vision, but it 

 is <>no almost wholly dependent upon the special judgment and 



perience of the observer. 



It we confine ourselves strictly to those aids to the impression 

 <>f solidity which are due either to optical effects or unconscious 

 judgment, and sum up our results as we are now in a position 

 to do, we may say that with the microscope, when one eye only 

 is used, we are on the whole far more restricted than in monocular 

 vision with the unaided eye. The perspective effects of distance 

 .uid of position in the field of view are practically absent, and 

 the image in the direction of the depth dimension is exaggerated. 

 < >ur main guides would seem to be the comparison with the 

 objects <>f known form, aided by the " inclination perspective"; 

 also the amounl of haziness or clearness with which the different 

 put- or layers of the object are seen, which is assisted to a 

 er or less extent by eye accommodation. 



W e come now to the subject of stereoscopic effect in binocular 

 vision ; and the first thing to recognise is that everything which 

 applies to <air impression of space relations with one eye naturally 



