re: Seeing in Stereo
I've been doing the cross-eye method for 40 years. To get the proper relief you need the right image on the left and the left image on the right. When I take photographs I often take 2 shifted a few inches so I can see it in stereo.
This technique is also great for doing circuit board checks. If you have one board you know is correct and the other is questionable, you put them down side by side and cross your eyes to blend them together. If there's any difference it jumps out at you. Much quicker than looking back and forth component for component. It's easy to see reversed diodes and capacitors, and incorrect or missing components.