Thank you for starting this nice discussion on stereo viewing Gtoal.
Let me add my little bit to this.
Considering parallel viewing : personally I can not actually diverge my eyes, I understand that most people cannot do this. This implies that the far points in a parallel stereopair for most people can not be further separated than the distance between their eyes, for adults some 6 cm. This limits the size of a P-viewable stereopair to 2 times 6 cm.
A lot of people experience a Cross-eyed viewed image as closer by and smaller than a Parallel-eyed viewed image. This is no surprise if we see the lines of sight in the image Gtol included. But I found that this difference is not noticed by all viewers.
Despite all tutorials on viewing techniques some people still struggle to learn freeviewing. A little bit more than 9 years ago I developed an easy tool to make cross-viewing a bit easier. Using a mask cut out of a sheet of paper can guide the line of sight and also block the two images left- and right from the perceived 3D view. (I think that I invented this as I could not find any references to this method but I am curious to know if other people found this before.) You can find it on my no longer maintained site on 3D:
http://slakje.jvonline.nl/3d/javimask.html
For picture enhancement I stumbled across ImageMagick (
https://www.imagemagick.org). It turns out to be a very versatile tool also for the manipulation of stereo pairs. In another part of this board I shared the windows batch files I use, including one to create LRL views from LR stereopairs:
viewtopic.php?f=16&t=35&start=20#p314
Jan a.k.a. stereomii
StereoPi with Waveshare 160deg cams