My time has come!
The above stereographic image is for cross-eyed viewing (most stereograms are wall-eyed, so you may need to put your finger in front of your screen until this one comes into focus)
This is an image of Honolulu, Hawaii, published by NASA. Note Diamond Head (the volcanic crater) in the south.
Here are some other stereopairs published by JPL:
Wheeler Ridge, California
Mount Saint Helens
Salt Lake Valley, Utah
Wellington, New Zealand
It varies per person. I for one can't view wall-eyed, only cross-eyed.
I have to exert constant effort to cross my eyes, don't you?
Also can't do parallel, only cross view. I only have to use effort for the first few seconds, as soon as the two images are aligned, my focus snaps to it and I can relax and keep the focus without having to think about it.
It does cause some mild strain if I'm doing it for too long (like going through a book of these), but if I'm cross-eyed for a just a couple of minutes its no problem.
Huh. For me I can very easily wall-eye, I just let my focus drift. Going cross-eyed requires serious and constant strain, and doing the trick with my finger in front of the screen doesn't work -- I can get the dots aligned but if I try to focus on the screen or move my finger I lose it instantly.
Are you farsighted?
Nope, slightly nearsighted (~20/25).
Same here basically, cross-eyed viewing is super easy for me but I have to work for minutes to perform wall-eyed viewing. I was really excited to see a post with cross-eyed stereograms.