3-D Stereo Viewing

(without the need for special glasses or viewers)


when viewing this in 3-D, you see 5 figures instead of four

and the three central figures are shown in full 3-D viewing mode.

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The flat screen is gone and you become part of the scene.



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Egyptian figurines
Stereo viewing methods
Cross-eyed vs Parallel viewing
Cross-eyed sample image
Common objects background
Spatter, scatter, splotch image

Basics

   The basic concept for looking at photos or graphic objects in three dimensional stereo is to duplicate what the eyes see normally. We have a distance separating our two eyes that is approximately 3", giving us actually two pictures of what is in front of us. These two pictures are not the same because of the separation, or "different viewing" location of each eye. We get one picture from the left eye and we get one picture from the right eye. However to avoid confusion, the brain merges these images for us at "focus" points. A focus point is the distance your eyes happen to be converged upon at any moment. 

   When our eyes focus, two things happen. The move inward or outward with respect to each other and they also elongate or flatten from the spherical shape. When you focus close our two eyes move toward each other and they become "longer", measured from the front surface to the retina they are egg shaped when looking close. When you focus on a distance the eyes move away from each other and they become "shorter" when measured from the retina to the front surface of the eye ball. This lengthening and shortening of the eye ball it self is an automatic function that we learned as infants and is linked to the distance that our eyes are converged upon. As our eyes move toward each other the eyeball elongates automatically to adjust for the nearness and be able to "focus" clearly on the object being viewed. This is one reason for needing glasses when you get older so you can read and see things closely. As we age, our lenses lose flexibility and can not conform to the smaller radius of the new shape of the eyeball in the elongated, or stretched out close up viewing position. What makes viewing stereoptic pictures without a viewer possible is the ability to fool our brain and make our eyes move outward from each other while focusing close instead of far, as the wider eye spacing demands by reflex action. So we must fight our reflexes and take our eyes of of "automatic pilot" and put them on manual for this operation. We need to focus in opposition to what is natural. This is what makes it so hard for some people who can not seem to "see" the 3-D images at all, regardless of how hard they try. I can guarantee you that as long as you have sight in both eyes, you can learn to do this. Everybody can do it if they have the patience to learn.

Methods of viewing stereograms  

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In this method you look through the object you are viewing but focus closer than the point in space that your eyes converge. This technique produces the clearest images with the least amount of eye strain.

We can view stereo pictures in two ways. The normal method is the parallel technique, shown at left. The alternate method is the cross-eyed technique shown at right. It makes a BIG difference which method you use, as they reverse the depth information of the stereo picture you are viewing. A parallel stereo picture's background will appear in front of the foreground figures if viewed using the cross-eyed method, and vice versa. If you cross eyes on a parallel picture the front objects will appear to be in the background. This is quite disorientating and makes me dizzy. It is easy with the cross-eyed technique to over do it and cross too much. With the parallel method, the tough part is bringing the picture into clear focus after you have merged the image pairs to a center figure.
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In this method you look in front of the object you are viewing but focus your eyes past that point to the actual pictures distance. This technique makes me a little dizzy and the objects seem too small.

Cross-eyed vs Parallel viewing

Some people can "see" OK using the cross-eyed technique just fine but can't see the depth when using the parallel technique. I have found that if you have a very wide separation of the stereo pairs then it is better to use the cross eyed method when building the stereoptic view. It is easier to make big differences in the eyeball positions using this method and larger pictures can be used. However for smaller pictures the parallel method is better because the added side effect is "telescopic vision", making the image that much clearer. This effect comes from the condition that exists when your brain thinks you are looking farther away than you really are and the eyes are seeing the object larger than it would be at the convergence of the eye's line of sight. So brain sees the object as being farther away than it really is but the image from the eye says it is much larger than it should be (or would be at that distance). The stereo shot of the Egyptian figures at the top of this page is the parallel type of stereoptic picture. To see the depth appear you must look "through" your computer screen and focus on the back of the set instead of the front of the tube. As your vision drifts through the tube you will see the images on the screen separate and give you "double vision". Your goal is to make this double vision progress until the image on the left and the one on the right both merge at a point in-between the two. When this happens then all of a sudden the flat screen will disappear and in stead of the figurines being part of the wall they are made from, they become vivid three dimensional figures standing in arch ways and the wall is many (virtual) feet behind them, while the upright pillars are placed at many depths, as are the pointed/scalloped ceiling patterns. The clarity of the scene multiplies as you become part of the picture instead of just an observer of a flat 2-D view. This particular stereo picture is just about my limit for viewing separation. If I wanted to make it longer for example, then I would think of making it a cross-eyed version. In the case of a stereo pair of photos, it is an easy matter to simply switch sides for the photos. Take the left photo and put it on the right, and take the right photo and put it on the left. This switches the technique you need to use when viewing. If you switch a cross-eyed pair then you will not be able to view them properly afterward unless you use the parallel technique. Below is a sample of "Cross-eyed" stereoptic picture. Do not overdo the crossing of the eyes, you only need to cross enough to bring the loops the distance between then, or one loop. You can tell if you have it correct by seeing how many of the sequences you can see the floating spheres with the 3-D view. Although there will be six loops visible to you only the ones on the extreme left and right will lack the three dimensional effect, and the four inside loops look great as they leave the flatscreen behind.

 

Cross-eyed stereogram


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    In this type of stereoptic picture you can use wider separation of images. Not the distance between the large balls in the center of each panel? This is how much of a shift you must make with your eyes to achieve the 3-D effect and using the parallel method is more difficult to employ here as your eyes can not shift outward as far from normal as they can shifting inward. 

    Often little focusing guide are added to the stereoptic picture so as to give the viewer a clue on how much shifting needs to be done before the brain says, "Oh, I get it... you are trying to focus. Here let me help..". When the brain clicks in then you become part of the picture and you can freely wander around the scene, focusing in and out within the picture itself. This method of helping the viewer "see" the stereo effect is used to a great extent on the random pattern type of stereoptic pictures, such as you see at the shopping malls from time to time. They look like nothing but a Jackson Pollack nightmare until you converge the two guide dots and create a third dot in between the original two. When this happens you will notice there are shapes taking place in the picture itself and as the shapes become clearer your brain will recognize what is going on and give you the boost you need to "Click into" the 3-D mode. Below is an example of this type of stereoptic picture with the guide dots in them. The scene doesn't look like anything but a bunch of coffee beans, however if you look "through" the picture while staring "past" the dots then they will seem to drift toward each other. When they merge you will see three dots instead of the original two. Just hold this for a few seconds while your brain catches up with what has just happened, then look at the picture without changing your focus and you sell see the depth becoming clearer until you are seeing it is three-dimensional clarity that exceeds your normal vision noticeably. When merged, the two dots below will be on the same depth as the background coffee bean pattern however as your eyes adjust to the new clarity with which you see the image, you will see a steaming cup of coffee emerge and float a few inches in front of the background, which appears to be around a foot into the computer screen.

 

Stereograms using common items like coffee beans 
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   This particular "stereo-gram" is composed of recognizable items, like coffee beans but most of these type of stereoptic pictures are made from random dots, splotches of color or other random looking patterns. Most of the stereo grams in my library are of this type. They usually have some written message or scene pop up when you bring it into stereo viewing, like the coffee cup in the stereo gram above. 

   This next type is more confusing to those who can not "see" stereograms. They watch us looking at them with awe and it drives them nuts because all they can see is a bunch of squiggly lines or splotches and spatters. At least in the one above the non-seers can at least recognize some coffee beans and the photo has a bit of merit on it's own as a background, etc... With the random spatter type it is a different thing. Check out the stereogram below and you will see what I mean. It looks like a bunch of worms to anybody who does not know how to view them. However, when you know how to view them, then you see two little wind-up toy drummers with their drums and drumsticks.

Random Pattern stereogram  

    As with the previous stereogram I have added the guide dots to correspond to the depth of the background pattern. The little drummers are standing several inches in front of this "dot" depth. You will see them emerge as your eyes get used to the focus of the background pattern. Sometimes it is easier to see these stereograms if you look at them from a distance of only a few inches so it is easier to "merge the dots". Then after they are merged (and way out of focus, by the way) then start backing away but DO NOT CHANGE YOUR FOCUS, keep the same focus so that you see three dots instead of two. As you draw back while maintaining the focus, the picture will clear up and you will see the images appear. I hope you enjoy your visit to my stereo gallery. Now that I have this section added to my site I will be on the look out for more of these as well as making up some actual stereo photo pairs of my end of the world, for you all to see. I need to make a little gadget for myself so that I can take stereo shots with my digital camera but that shouldn't take long to make. I have some ideas that ought to work out OK for "nonmoving" shots. When I get the details worked out I will put them in the gallery also. 
 

 

  Due to the limitations of a CRT (your monitor screen) the stereo detail is much better if you down load the picture and print it out at your printer's highest resolution... Viewing the printed stereogram is much more detailed and sharp.

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