Viewing Considerations & Compromises
A comfortable reading distance is a good starting point for viewing stereograms on-screen or on a page. However, drawing back from the image may not only help in viewing larger images, but increase the 3-D effect. Also, I find the longer I stare at a stereogram, the greater the stereogramic effect.
Bringing a stereogram into focus is a gradual sensation, but switching from "stereovision" to normal vision can be abrupt, and may be uncomfortable for some people. The best way to avoid any such discomfort is to breakaway from the stereogram by briefly closing your eyes, and then opening them using normal vision.
All Color Stereo stereograms are made to be viewed wide-eyed, AKA: parallel vision.
How can you tell if your using wide-eyed or cross-eyed vision?
Many times I realize someone is viewing cross-eyed instead of wide-eyed vision. As a result, they miss the correct 3-D effect, likely seeing an inside-out effect. Unfortunately, there's no easy way to tell or coach the casual viewer, but keep in mind that stereograms using parallel vision may actually feel soothing to the eyes. Whereas, images requiring cross-eyed vision can produce enough cumulative eye-strain to produce a headache if your eye muscles are not use to it. In my experience, staring at enough images on a regular basis develops the eye muscles (like exercising any other muscles) to a point where you can view with total comfort– unless of course you create stereograms for hours on end, in which case, nothing can save you.
Why you might see a double image: This depends on many things that have to do with how the stereogram is viewed and the image itself. You would likely see a leaner image layered above a wider image giving a double layered effect. This is from diverging your vision too broadly. Stereograms are made of vertical columns. If vision diverges too much, your brain will factor in two columns at once instead of single side-by-side. This happens most often with narrow parallax or viewing an image from too far away. It also may happen with experienced viewers who can diverge their eyes more easily.
Why you might see some, and not see other stereogram effects:
There are a couple reasons you might see stereo effects in some stereograms, but try without success with others.
1) you may be using the wrong vision: cross-eyed instead of wide-eyed
2) your monitor size and screen resolution may be too small, or too large.
Or, it could be a combination of the two. Sometimes, in the frustration from being unable to view stereogramic effects due to inadequate monitor/resolution sizes, a viewer might try too hard and end up using cross-eyed vision where only wide-eyed will work.
The images on this site were all created at far larger sizes for my print publications. As a consequence, there is detail and quality that is necessarialy sacrificed to display an image on a computer screen. For maximum detail, please consider purchasing one of my books. Stereogram iPad apps are also better for viewing.
Please see my Publications page.
The final web image is again compromised by the compression-quality ratio inherent in the JPG image format. I have mostly used 6 on a scale of 10, which means image quality has been moderately sacrificed, but still quite adequate.
Presentation of a stereogram is best served by as little distraction on the page as possible. Especially any kind of stray patterns or words on either side that can create visual dissonance.
Color accuracy is always desirable, but makes no difference whatsoever with the 3D effect. All images should show a 3-D effect if reduced to grayscale or even just black & white.
It's a lot of compromising, but my justification is to raise stereograms to a high art form and bring pleasure to those people who find their way to Color Stereo.