Three square peep windows
are to be placed in front of the eyes.
L - the left-hand window, meant for the naked eye (without any
intermediary optical elements)
M - the middle window, meant for the eye watching through two
plane mirrors, to get the superposition of field A on field B,
resulting in image (A+B)
R - the right-hand window, meant for the naked eye (without any
intermediary optical elements).
To contemplate the bioptical painting,
one looks first through windows L and M. After watching the bioptical
effects, after a lapse of time depend on the viewer`s adaptation
capacity a second stage follows, watching through windows M and
R. Important reversals occur in bioptical effects, both in point
of the space placement of elements and in the perception of colour
combinations. Short-sighted viewers who usually wear spectacles
should use them also in this case.