--- George Brock-Nannestad <[log in to unmask]> wrote:

> Now, if I look at many stereo pairs (it comes in bursts) I have
> until now 
> been able to train my eyes to be wide-eyed, and then I can see
> without a viewer. 

Being able to "free view" stero pairs is a pretty easy
practice to learn, and many stereo pairs published in
books and magazines are printed for free viewing, or
for those who cannot manage that, viewing with a small
plastic hand-hald viewer that has a pair of lenses
similar to a Holmes viewer.  However...

> However, John R.T. Davies once taught me that by crossing
> your eyes, 
> which is considerably easier and may be trained to painlessness,
> you can instantly see many stereo pairs in 3D. 

Speaking strictly for myself, I have *never* been able to
view stereo pairs cross-eyed, and when I try it's quite
painful. Also, publishing pictures switched for cross-eyed
viewing makes their viewing with any aid such as the
viewer mentioned above impossible.  When you view
standard stereo pairs cross-eyed, what you are seeing is
what's called "pseudoscopic" stereo, in which the objects
closer to the camera appear to receed into the background
and vice-versa.  You can get some interesting special
effects with pseudoscopic stereo, but it's far from a
natural view.

David Breneman         [log in to unmask]

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