Digital 3D Stereo
The ability to view 3D images (parallel
views and cross-views) without the aid of glasses
is a nice skill to have, and it can be mastered easily by most people. Several methods
are described below to help you learn to "free-view" both
cross-eyed and parallel stereo views.
The cross-view technique is
generally easier to master and should be tried first.
Then, give the
parallel method a try. Parallel is the method most often used in stereograms
(stereo cards), such as those which were so popular from the Civil War
period up until the mid-1900's.
Free-View 3D Images
All photographs, images and text on this website page copyright Michael Beech
Detailed information about 3D, including techniques for avoiding alignment errors, proper 3D photography techniques, methods for correcting alignment errors, and easy ways to align 3D pairs without window violations can be found in the Digital 3D Stereo Guide and other publications.. How to do 2D to 3D conversion is explained in detail in the book Mastering 2D to 3D Conversion.
More Free 3D Tips
Tips # 13
through 18 Coming Soon
Please check back.
First, let's try cross-view. Cross-views or X-views are
displayed with the image for the right eye at the left and the image for the
left eye at the right. In order to view these, you must cross your eyes such
that the right eye looks at the left image and vice-versa. The training
technique is quite simple.
Using the image below, we'll try the quick
method first . . .
While looking near the center of the black
rectangle (near the white dot between the images), slowly cross your eyes
and watch the images move toward each other. When they overlap exactly, they
will merge into a 3D image. Tip: Be careful not to tilt your head to one
side or one image will seem to be higher than the other.
If you use glasses, you should be looking through
the part of the glasses that keeps the screen in focus for you.
If you are still having trouble, try this:
look at the white dot at the center of the black rectangle. While keeping
your eyes looking at the dot, hold up a pointer, such as a pencil or your
finger tip, between you and the stereo pair. There will seem to be two ghost
images of the pointer. Don't look at the pointer . . . keep your eyes on the
dot. Move the pointer toward you or away until the ghost pointer's tips seem
to be centered in each of the images. Keep the tips of the ghost pointers
level by slightly tilting your head to the left or right. Once you have a
ghost of the pointer tip centered in each image, look at the pointer tip.
You will see that a 3D image has appeared behind the pointer. Now you can
move the pointer out of the way.
A slight variation of that technique
is to start with your pointer tip near the screen and right on top of the
white dot. Without taking your eyes off of the white dot, move the pointer
toward you. You will see the pointer seem to become two pointers. Keep your
eyes focused on the white dot, but manuever the two pointer tips until you
have one centered in each image. Look at the pointer tip and a 3D image will
appear behind it. Move the pointer out of the way.
After a bit of
practice you will be able to look at a cross-view stereo pair and cross your
eyes to quickly fuse the two images into 3D with very little effort.
Try the images in the Cross-View Gallery and the
Cars in Cross-View Gallery
to Free-View 3D
Now, let's try to parallel free-view. This may
seem harder, but it is actually pretty easy once you understand what you are
trying to do. First, you will note that the image provided is smaller. This
is because it is hard for most people to separate their sight-lines wider
than the distance between their pupils. For this reason, the first sample
image is very small. Don't enlarge it on your screen. If you use glasses,
you should be looking through the part of the glasses that keeps the screen
Keep in mind that your goal is to try to allow the
sightlines of your eyes to diverge slightly as if you are looking at an
object far away. This is actually a muscle relaxation instead of a
contraction, so just let them relax as you would when tired. If you want,
you might try that on the image below . . . who knows, it might just work
for you the easy way. But if that doesn't work, one of the following should.
piece of cardboard that is about 12 inches (30cm) long, such a the back of a
yellow scratch pad. Place the cardboard vertical to the screen so that it
divides the black rectangle in half with one image on the left side and one
image on the right. It should be sticking straight out from the screen.
Place your nose against the edge of the cardboard so that your right eye can
see only the right image and your left eye can see only the left image. Just
relax your eyes and let them do their thing. The images may wander around
for a moment, but eyes automatically try to fuse similar objects together
and, if you give them a moment, they'll get it right. In fact, you won't
even be able to stop them from fusing the image into 3D. If this small one
works for you, then try the larger ones below for practice.
Tiny Parallel Stereo Pair
Another method to learn this skill is this: print the
above image onto a piece of photo paper (so it will be fairly stiff). Trim
off the top of the paper exactly at the top of the image. Hold the stereo pair
at arm's length and look just barely over the top at some distant object
across the room.
While looking at the distant object you will see that the two images have
begun to merge. Move the print upward into your line of vision and you
should see the 3D image fuse and form.
Sometimes a larger image will
work better for this technique, so print these out also.
Small Parallel Stereo Pair
Medium Parallel Stereo Pair
Near Full Size Parallel Stereo Pair
I hope this exercise has been helpful and successful for you. If not,
don't be discouraged; you can always use a parallel viewing aid, such as a
Holmes stereoscope or a plastic lorgnette (was $3.95 at
http://www.3dstereo.com/viewmaster/svn-lorg.html ) to view parallel
stereo images and cards.
Good luck in your stereo viewing and best wishes,
Try the images in the Parallel View Gallery and the
Cars in Parallel View Gallery