In these cases, the object is depicted by the two half images of a stereogram or by the contents of the autostereogram.
This is shown clearly by Emmert's law, in which the apparent size of an afterimage (e.g., the bright spot we see after looking at a camera flash) is influenced by where it is viewed.
It is consistent with the geometry of the world: an object with a particular visual angle (given by the size of the retinal image) must be large if it is far away and small if it is near.
At six meters, to view an object without double vision the optic axes of the eyes are essentially parallel (no convergence).
At closer distances, to view an object without double vision the optic axes need to approach each other at an angle (increasing convergence).