The degree to which spherical aberration can hinder the seeing of objects sharply, and to which thesharpness of the image depends upon the size of the pupillary opening, can be convincingly shown tothe shooter by means of a simple example. Small orienting marks and objects which can bedistinguished only with difficulty during overcast weather become incomparably more discernible ifone looks at them through a small peep hole which, in this instance, fulfills the role of an artificialpupil.