| Creating Stereograms By Owen Ransen | |
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Have seen those plastic viewers (sometimes sold to tourists) which look like a pair of low quality binoculars? When you look into the viewer you see, in amazing technicolor 3D, sights from the city you are touring. (When I was a lad they were called "Viewmaster.") I will now explain how you can get the same effect with your own photos! You will need:
- A normal inexpensive digital camera (I have a Sony DSC S50).
- A good quality photo printer (I have an Epson Photo 1290)
- A paint program (I use Paint Shop Pro 5)
We see in 3D because we have two eyes, each giving a slightly different view of the same scene. Our brain (25% of which is dedicated to sight and vision processing) interprets the two images and gives us an accurate idea of the distance of objects.
You can see how this works by doing the following test: Look at the top left corner of the monitor and close one eye. Now, with one eye still closed, move your head to line up something beyond the monitor corner with the corner. A window or a shelf, whatever. Now, without moving your head, close open eye and open the other one. The thing you lined up with the corner of the monitor is no longer lined up! The visual position of things change from eye to eye. This difference in the the two images is what the brain uses to calculate distance.
Here is an example of that:
Imagine taking two photos of the same scene from slightly different positions. You are simulating the two different views your eyes would see. Here is how to make these two photos. When you take the first photo note what is in the center of the image. Then move the camera about 3 or 4 inches to the right, point the camera at the same central object and take the second photo.
Tips on taking the photos:
- Do not take photos of moving objects, that will confuse the brain when it tries to merge them into one image. If you want to take a photo of your cat or dog he or she must be asleep!
- Have a good "central reference" so that the two images point at the same thing.
- Do not be tempted to make the difference in distance between the two shots more than 4 inches. Your two eyes are not 4 feet apart!
- Always do the left image first and then the right image. If you don't get into this habit you will never know, when you come to print the photos, which is for the left eye and which for the right eye. Swapping these by mistake means cross eyed headaches! Most digital cameras name the images with consecutive numbers.
Right, now you have your two photos and you have transferred them to your computer. Your next step is to make and print an A4 page something like this:
If you are unsure about how to create the above page I have provided a template (right click here and select "save target as" to get Template.png) for you to download. Open the file in your favorite image editor, add in your photos, and print it at A4 size.
Tips on making the page and printing:
- You should resize both images (Image menu, Resize item in PaintShopPro for example) by the same amount.
- Digital photo images which are 1024 wide should be resized by about 33% if you are going to paste them onto a white A4 page which is 1024 pixels wide.
- Place the images as close to the top center of the large white page. (In PaintShopPro you do a control-C in the reduced size image and a control-E to paste it into the large white A4 page.)
- Use the best image quality and color settings for your printer.
- Use recycled old paper for your first tests, save a tree!
- Remember to get the left and right eye images correct.
Now the hard part, viewing the images! When you have printed the images...
...you should cut them into a single narrow horizontal strip and hold them in from your eyes...
The distance should be somewhere between 6 to 18 inches, depending on whether or not you wear glasses, are near-sighted or short-sighted or have perfect vision. You will need to experiment.
Now the really really tricky part, I wish I could be there with you to give you aid and moral support. You have to look beyond the top of the photostrip into the distance. As you do that you will notice that, in the bottom of your visual field, you see 3 or 4 images, maybe a bit blurred. The trick is to relax the eyes so that the central two images, which probably already overlap, become a single "fused" image. The fused image will have that 3d effect of depth and reality. Remember, you will need to experiment with distance to find the best position for you own eye/brain combination!
Here is an approximate simulation of what you will see:
Once you have done it once it is easy to do again, but the first time it make take a bit of effort!
I have provided one example which you can download and print to try out before you start taking your own photographs. Right click on these words and use "save target as" in the menu which pops up.
Have fun! Don't go cross-eyed!
