Accommodation of the 
lens turns out to be quite 
effective—–as far as it goes. But 
experiments show that it seems 
to be effective for only a short 
distance, up to a few feet. 
Beyond that, observers simply 
cannot discriminate between 
one distance and another by 
means of this factor. Whether 
an object is 5 feet away or 50 
feet away, a person in a dark 
room looking through one eye 
is as likely to judge it to be 8 
feet away as to judge it 
correctly. With several objects 
visible, provided the nearest is 
beyond a few feet, observers 
will typically report that all of 
them are equidistant. These 
results are not surprising when 
one considers that, beyond 
several feet, objects at differing 
distances will all be in 
relatively sharp focus. 
Therefore, accommodation 
changes are not so necessary at 
these far distances.