1. Crossed-eye stereopairs

A few years ago I found a few images on the web that impressed me greatly. I am talking about stereo-photos of minerals. For now there is a lot of ways of viewing 3D images: 3D TV, virtual reality glasses, stereoscope. But there is one method of viewing 3D images that requires no special equipment at all. It is stereopairs viewing.

The easiest way to learn viewing stereopairs is the cross-eye method. Learning to view stereopairs is somewhat similar to learning riding a bike. When you try it for the first time, it take some time to learn, you fall and try again. But once you got the skill, it remains with you for all of your life. After you have learned to view stereopairs, it takes less than a second to focus and to see a 3D-image.

The learning won't take much time. Younger friends of mine usually got the new skill in 1 to 5 minutes, some others learned for up to half an hour. Some of you may ask: "Isn't eye-crossing harmful for your sight?". No, it isn't. It is even good for your eye muscles, as they are training during the process.

Here is a picture with "planets" - special simple picture ideal for training. To see the 3D-effect for the first time, you should first train and try with this picture. After you saw the 3D effect on it, it will be easy to apply your new skill to mineral stereo-photographs. Before you start trying please read the instructions below.



Instructions.

1. First make yourself sure that you can bring your eyes together staring at the point of your nose. For example when staring at your finger and moving it closer and closer to your face. (look at the picture on the right :)

2. You should sit right in front of the picture on you monitor. You should stare right into the center of the photograph, and your stare line is at the angle of 90 degrees to the screen. You should keep your head exactly- the line connecting two identical points on left and right images must be parallel to the line connecting your eyes. Even a small lean of your head can prevent you from seeing the 3D image.

3. While looking onto the stereopair, you should let loose your stare (some call it “un-focus”), do not concentrate on details, and look straight into the middle of the line separating left and right images. Now you can start to mow your eyes. To make this process easier you can take a pencil into your hand and bring it to the line separating the images. Then move the pencil slowly towards your eyes, looking at its end, but watching the picture in the back. Important moment, you look at the pencil but at the same time you watch the picture behind it, like with a corner-eye vision.

4. The left and right images will begin to bifurcate. Maybe you will see 4 images behind the pencil. But at the correct pencil position 2 of them will unite, and you will see pencil and three images behind it. The middle one of them is the 3D-image that we want to see.

5. Then you should draw your attention to the middle image, but not moving your eyes. Middle image will eventually become focused, and you will see the 3D. After you saw it, you can look at any part of the image, studying every detail, like with normal image. The deal is done!


To those who already learned the trick I offer to enjoy some minerals in 3D:

2. The details that cannot be seen in 2D.

Viewing stereophotographs isn’t just an entertainment. For many years in science articles and magazines it had been a standard of representation of objects, when it was necessary to make an accent at their shape, e.g. complex molecules in biochemistry. There are some cases when details that are not seen in 2D can easily be distinguished in 3D. Here is an example:







When looking at the pictures above in 3D, you can easily see the shape and mutual position of inclusions. And it becomes absolutely clear that yellowish inclusion lies inside quartz, not on its surface, and you can see at what angle it goes inside. Look closer at the shape and location of negative crystals filled with liquid and gas. It is much harder to distinguish their shapes in 2D.

The next photo reveals some interesting aspects about inclusions too:

3. High resolution stereo viewing.

For those who already learned how to view ordinary stereopairs, there is a greater opportunity.
It is viewing high resolution 3D images with zoom capability. The amount of details which can be seen in a single photo strikes and amazes. Full resolution viewing is as superior in compare to ordinary stereopairs, as ordinary stereopairs are to 2D images.

UPDATED on 26.11.2020: and now you can zoom-view stereopairs directly in browser, here on Mindat!
For instructions and information follow here:
link 1
link 2

Another alternative is special software.
The software exists for both Windows and MacOS. I myself used only one viewer for Windows called StereoPhotoMaker. The program is freeware, doesn’t require installation, and weights 1,5Mb which is less than one photograph. Latest version can be downloaded from the developer’s site: http://stereo.jpn.org/eng/stphmkr

4. How to shoot stereo images

And final few words concerning how to shoot stereopairs.
It is a very-very simple process, especially in compare to the extreme macro stacking photography that many people here at mindat do with amazing results. You should just take two photos of the specimen, standing on a rotation stage.

There must be an angle of 90 degrees between the rotation axis and the line connecting the object and the camera sensor. Between the two shots rotate the specimen. Rotation angle is chosen each time experimentally. Usually it is near 5 degrees.

Then put the two shots into StereoPhotoMaker, press one magic button called “auto alignment” and stereo image is ready. You can then retouch it as usual. Also instead of rotating the specimen you can move the camera around it, but I find rotating the specimen simplier. There is also a way of creating a stereopair from a single stack in stacking software, when shooting big stacks. But for now I hadn't much success with it, the resulting image appeared to be of poorer quality than a "natural" stereopair.

There is an excellent article by Tony Peterson at mindat about making stereo from a single stack and nuances of photos processing:
http://www.mindat.org/article.php/2182/On+generating+stereo+images+with+focus+stacking+software

All photos used in this article are shot with Canon MP-E 65mm, Canon 40D, StackShot rail, and stacked using software from Zerene or Helicon.

5. An important question to you

To all those who have read this article, and have tried the method described. I kindly ask you to write a comment here with answers to these questions.

Your feedback is really important for me!

1) Have you succeeded in seeing 3D images?
2) Have you succeeded with the “zoom viewing” using software?
3) What are you thinking about quality 3D photography of minerals? Can it help to show the minerals somewhat better that 2D or it is not worth the effort?

Thank you everyone!
I would like to close the article with this photo. Though the photo itself is not perfect, the specimen is among my favourites.


This article is based on the publication by Dmitriy Dolivo-Dobrovolskiy and Eugeniy Fedorov "Sterepairs and how to view them", 2007 (text in russian): http://macroclub.ru/how/stereo