Stereo Problems occur where a close object obscures distant objects for one eye but not for the other eye. Because these items are not seen with both eyes, they cannot have a stereoscopic effect. In real life we can move our heads to overcome this problem, but stereo failure in regard to small items of the photo is a defect of stereoscopic photography.
In pictures showing obvious stereo failure, you also get double vision.
Looking at a distant car, it is seen in stereo but the near car will be seen double, and vice-versa. The brain computes stereo when there is a slight difference between the images seen by each eye. If there is a big difference, we adjust the eye convergence to and correct this problem.
Anaglyph Window
Stereo windowing involves tinkering with the distance into the image occupied by the edge (or frame) of the picture.
The stereo window is set by:
deciding on an object which is at the desired window level.
Arranging the object to be equidistant from the adjacent vertical margin on the two pictures.
It is not necessary for the two vertical frame edges to be at the same level.
The edges do not even need to be vertical although tilt will occur.