Autostereogram

[Karl Cunningham]

James G. Sack (jim) wrote:
> On 04/09/2010 06:24 PM, Tracy Reed wrote:
>> On Fri, Apr 09, 2010 at 12:41:07PM -0700, James G. Sack (jim) spake thusly:
>>> A fun page:
>>>   http://en.wikipedia.org/wiki/Autostereogram
>>>
>>> I don't remember running into this kind of visual effect before.
>> These were popular in the early 90's. Sort of the "Velvet Elvis"
>> artwork of their day. They used to be for sale in malls etc. I have
>> never been able to properly see one of these. I don't know why. I have
>> tried focusing and relaxing and diverging and everything like they say
>> but the image never appears for me.
> 
> For me, some are harder than others, but by starting with my head about
> 16  inches from a full-screen image, and concentrating on looking
> "beyond" the screen, I can usually get them to "snap in" in 5-30
> seconds. Once visualized, I can pull back to a couple-feet or more.

I remember a program to generate them on a printer. One of the inputs to 
the program was the viewer's interpupillary distance. I think this needs 
to be reasonably close to easily view one.

Something which might help viewing (not tried) is to make two small 
holes in a (properly scaled) printed autostereogram separated by the 
viewer's interpupillary distance. Then stare at the holes, making them 
converge into one, and see if you can see the picture in your peripheral 
vision.

Karl