"You might have seen SIS, "single image stereogram" images around for many years. They look like squiggly
lines on paper until you learn to look at them in a special way. Many times people get frustrated and give up
after a few minutes. They often think that they are simply not gifted with the ability to see them, or that it takes
some special talent, or that they have some kind of vision-deficiency. While sometimes that may be the case,
often it is just that they haven't been properly introduced. While the trick of seeing SIS images doesn't qualify
one for any special award, it is an interesting and pleasurable skill once learned, and I find it actually helps
one to learn to see a lot of other things in a new way."
"A simple 3D image appears below, one that most people find quite simple to "get," it is a series of two
concentric rings, that appear in depth. If you look mostly at the center, a spike will appear, the contour falling
back to a great illusion of depth, with the circular waves surrounding it. If you let your eyes unfocus, or force
them by getting too close to focus and simply rest your eyes on the etched lines, perhaps pushing the paper
slowly away, in time your brain will rescramble and reinterpret the shapes into a sense of depth.
Remember that most of vision actually happens in your brain. Your eyes simply supply stimulus that is
always reinterpreted in your visual centers. I think that is why most people can see SIS images after all,
given a little time and patience."
Intro to SIS Images

By Lawrence P Kaster
Texture map
Depth map
"After viewing the simple SIS image provided look at a few more soon after, but just for a few minutes at first.
If you make it a practice to look a couple times a day for just a few minutes, your eyes will soon learn not to
interfere with the process. What happens a lot with first-time viewers of SIS images is that just before the 3D
effect happens, a part of the brain will kick in with a kind of denial. The pattern seems to shimmer a bit and
then that part of the brain shouts "no," wordlessly denying that something really cool is about to happen in
front of your eyes. That is perhaps the most interesting thing about viewing SIS images to begin with, which
is a learning experience about how little we often allow ourselves to "see."
"A little eyestrain can occur if you are too enthusiastic, especially at first, but once you learn the "trick" of
unfocusing and refocusing in stereo, it will happen so quickly that the eyestrain will stop happening. New
muscles get flexed and relaxed around your eyes, and you will begin to see "stereo" in superimposed
complementary colors, and in unintended SIS patterns that occur often naturally. Stripes will "swim" and
checkerboard patterns stand out in surprising relief, if you get really proficient in this kind of "seeing."
Look around yourself and be amazed at your new ways of seeing!"
How SIS images are produced

"The stereo image is created using two kinds of images and digitally combining them.
The first is s "depth-map," in direct terms, it is a map of what part of the image will be forward and what will
recede. It is a gradation of white on black or black on white with subtle shadings of gray to indicate the
in-between or neutral positions in depth. The other image is a pattern, or texture-map that is superimposed
on the depth-map, and whose pattern is distorted by the digital program in accordance with the lightness
and darkness of the depth-map. That may be more information than is needed to enjoy the image!
But it may also help to appreciate the creative effort put into both kinds of mapping,
the result is a fascinating stereo image."
"The SIS images I make often have a very innovative addition that many find very helpful in seeing them in
stereo. I have placed a "shadow" of the major shapes on top of the print that give a basic clue as to the nature
of the 3D hape found among the lines. If the pattern is strong enough within the "shadow" area the shape will
alternately appear in relief, and then in depth, depending on which part of the image you rest your eyes on.
Sometimes it will be a mere suggestion, other times it can be made very dark and distinct, or tinted in an alternate
or complementary color. These SIS images are unique to my way of producing them, and make it easier to enjoy
the forms in the print from a distance, and with a simple glance, which make them more suitable to be framed
and hung on a wall. This way it is only incidental that the print has astounding depth when viewed carefully."      

                                                                                               --Lawrence P Kaster
All images and sounds © LPKaster 2008
Woodborough, Wiltshire  "Sunflower" crop circle
"Mayan Shadow"
Some examples, E-mail me at lpkaster@lpkaster.com for much more:
See Stereoboxes,
art panels with printed SIS Images.