Sticky

#### 3D Photographs: Anaglyphs, Crosseye and Parallel

What 3D pictures are

They are a realistic means of giving real depth to pictures so that the human eye / brain / mind has a strong sensation of depth as it would when looking with two eyes at the real world. In all cases there are two images which must be fed independently to the two eyes of the person viewing them. The technique of doing that is what makes the methods different.

This can be achieved in 3 ways - with red-green anaglyphs, cross-eye and parallel viewing. There are advantages and disadvantages to each. Glasses are needed for red-green anaglyphs, and the other methods can be viewed without equipment (or with a different type of glasses for each for ease of viewing).

Cross-eye pictures

In the cross-eye method, there are two pictures that are similar and the right eye looks at the left image and the left eye at the right image. This is achieved by making the eyes go crossed until the correct two images line up at which point there are 3 images and the one to concentrate on is the middle one. The technique is difficult for most people at first but rapidly becomes easy to achieve.

The advantage is very clear pictures with no limitation of size. The disadvantage is needing to learn the technique.

Cross-eye pictures are the same as parallel with the two pictures swapped around.

An example: Sword Fighting

How to view 3D cross-eye pictures

Here are the steps to see the picture in 3D:

1. Simply display them on your computer screen, in original size, not in full screen mode and sit about 0.5 metre (or 1/2 a yard will do) directly in front of your screen. If you are long sighted then 1 metre (1 yard) may be easier.

2. Go cross-eyed so that the 2 images become 4 images.

3. Vary the amount of cross-eyedness until the inside 2 images are in the same place - i.e. the left one of the right pair and the right one of the left pair coincide.

4. Now try to make your eyes focus without changing how cross-eyed you are, even though the distance is wrong. When the eyes see 3 images (as 2 coincide) the middle image is the one to look at.

5. Suddenly bang it will be in glorious 3D. Once you get practiced it gets easier.

I am not responsible for any eye strain or headaches! Stop before you do any permanent damage ;-)

If the above description does not work for you, then try this:

One way that helps with this is to hold up a finger about half way between your eyes and the 3D picture and to focus on that finger. As you move it towards and a way from you the images will move and at some point you will get 3. At that point keep your eyes cross-eyed the same amount and focus on the middle of the three images.

It does take some learning of the technique, but once you get it, then it is easier each time. There are a lot of 3D pictures in flickr, some of the cross-eye type and some of the coloured glasses stereo type. These later are easier to see as long as you have the glasses.

Good luck and have fun!

Another description of how to view cross-eye, in case my description doesn't work for you.
3D crosseye trips

A third alternative description which also includes a nice animation of what you should see and other useful information.

People who cannot free-view are missing out on some spectacular visions.. This test can determine if you can see Stereo images and how you see them. Once you have mastered the technique, your world will open up to 3 dimension.

Parallel pictures

In the parallel method, there are two pictures that are similar and the left eye looks at the left image and the right eye at the right image. This is achieved by making the eyes look straight ahead into the distance until the correct two images line up at which point there are 3 images and the one to concentrate on is the middle one. The technique is difficult for most people at first but rapidly becomes easy to achieve.

The advantage is very clear pictures, but there is a limitation of size. The disadvantage is needing to learn the technique. Some people find one out of cross-eye and parallel easier than the other.

Parallel pictures are the same as cross-eye with the two pictures swapped around.

Anaglyphs

Viewing anaglyphs (also called stereoscopic pictures) is much easier for a beginner than the other two methods, but requires having special glasses. You remember the old red and green glasses in a cardboard frame? That is what you need to view these pictures. The pictures in this case have been processed so that the the image for the left eye shows in red and that for the right eye in blue-green. These two images are on top of each other, so that part of the picture may look normal and part have weird red or blue-green ghosts around them. There are more fancy versions of the glasses which I am told are better.

The advantage of the anaglyph method is the ease of seeing the picture in 3D. The disadvantage is that there is some colour and clarity loss and you need special equipment.

An example: Close up of Fungus

How to make 3D pictures

For those interested in making their own 3D pictures, I wrote an article on my blog describing what I do more or less. How to make 3D pictures. This is for the cross-eye method.

Some tips on alignment and window violation issues by luc-fotos.

Have fun!

The Cha Cha

When two pictures are taken from the perspective of a person's two eyes, then the camera must move a little between the two pictures being taken. This is called the cha cha for the obvious reason. Well, a 3D anaglyph picture is worth two thousand words and here is a 3D picture of the cha cha being done courtesy of B. Allen Andersen.

Of course, when you are in a moving car, train or plane you can take pictures in rapid succession to make 3D pictures from. It is best to point the camera at right angles to the direction of motion. In fact movies can be taken this way by taking a single movie and then pairing it with itself displaced a little in time. I guess this is a cha cha cha. ;-)

Windows and Frames

3D pictures can be enhanced by having a frame around them. Whether or not they have a frame consideration needs to be given to where the left and right pictures finish on the sides as this determines whether the picture appears behind or in front of the screen of maybe some of each. Shahrokh Dabiri has written two tutorials about What is Stereo Window? and What is a Floating Window?.

Air Tight Frames and Out Of Frame Effects

Getting creative with 3D effects is the subject of the group 3D Creations, and in particular interesting framing and out of framing techniques are discussed in detail in the thread Air Tight Frames and Out Of Frame Effects with some excellent examples. There is even Software for doing frames on 3D pictures.

2D to 3D Conversions

These are much more work than when taking two photographs because everything must be constructed from a single image. That means making a second image and moving things about and distorting them so as to place each part of the picture at the correct distance. Here is an example of 2D to 3D conversion of an Eduardo Delabarra cartoon by The Wagman. It also includes an animated gif that shows the process of the changes he made.

A step by step demo of how to do 2D to 3D conversion.

Dan's animated GIF of slices involved in 2D to 3D conversion.

Mathematics of 3D (not for the faint of heart)

* A Comparison of Camera Base Calculation Methods by J. Bercovitz and Kiewa Valley Stereo
* Principles of stereoscopic photography using an ordinary camera by John Wattie
* Bercovitz Formulae for stereo base by John Wattie

Groups

* Stereophotography This is the largest group and accepts both types of pictures.
* Anaglyph (Red-Cyan 3D Pictures)
* 3D CrossView stereo photos
* 3D Cross-view only
* 3D Snapshots
* 3D stereo portraits
* 3D Stereograms these are the magic eye things.
* 3D Stereo Creations, Art, Manipulations & Games for manipulated 3D and PhotoShop Tennis in 3D.
* Hyperstereo for widely spaced camera 3D.
* The Best of Stereography.
* 3D Aerial Photography

Recommended tag usage

For red-green stereoscopic 3D pictures you are recommended to use 3D and anaglyph. When searching there are also many with stereoscopic and stereophotography. The tag stereogram is more often used with magic eye pictures, but has been used for some red-green pictures also.

For crosseye 3D pictures you are recommended to use 3D and crosseye. When searching there are also some with crosseyed.

For parallel 3D pictures you are recommended to use 3D and parallel.

For aerial 3D photographs also include aerial3d.

Finding 3D pictures

* Most Interesting anaglyph OR stereogram OR stereophotography OR stereoscopic
* Most recent anaglyph OR stereogram OR stereophotography OR stereoscopic
* Most interesting 3D AND crosseye OR crosseyed
* Most recent 3D AND crosseye OR crosseyed
* Most interesting 3D AND parallel
* Most recent 3D AND parallel

Note that parallel and crosseye(d) are used commonly as tags for non-3D pictures, as is 3D, so it is important to use 3D in conjunction with one of these to make it easy to find pictures. Also, some people have used 3-D rather than 3D, so you can try more combinations than the above.

Yahoo Anaglyph Group has many fine anaglyphs and is sent to and received by email.
The anaglyph group archives are stored at AB Archive with 37,000+ anaglyphs.

Schillr web site shows flickr pictures and allows the user to choose how to display all pictures, as anaglyph, cross-eye, parallel, wiggle etc.

Software for helping make 3D pictures

Stereo PhotoMaker 1.0
Stereo Maker
Stereo Maker
Anaglyph Maker
Anaglyph Maker 1.04
AnaBuilder
Software for doing frames on 3D pictures.

My thanks to another Ray for mentioning many of these software packages. I had never used any of them. I now have Stereo Photo Maker and it is a good program.

Equipment for helping with 3D

* Build your own 3D glasses.
* How to make 3D glasses for anaglyphs
* Free 3D glasses.
* Buy 3D glasses and other 3D supplies
* World's Cheapest 3D Stereoscopic Digital Camera by Neil Nathanson.
* www.3dstereo.com/ has many different 3D supplies.
* A Two-mirror Stereographic Beamsplitter that you can make yourself for any camera.
* Lorea 3D for SLR allows taking 2 pictures at once with correct spacing.
* Device for taking stereo photos by Jose Rodman.

3D Terminology

Alignment: When the two images are properly aligned so that the eyes and brain easily make them mesh. This involves vertical, horizontal, rotational and magnification issues as well as movement only horizontally.
Anaglyph: A picture that needs glasses to be viewed, usually red and cyan.
Cha cha: A method of taking pictures with a single ordinary camera by moving a little horizontally between two shots.
Crosseye or crossview: A picture that is viewed by going cross-eyed so that the left eye sees the right image and the right eye sees the left image.
Frame or Window Violation: when the foreground sticks out in front of the frame, which is not desirable.
Hyper: When the two photos are taken with a wider spacing to make the depth effect stronger. Often used for scenic photos especially.
Parallel: A picture that is viewed by each eye looking at the image on the same side which is achieved by looking into the distance. This can be harder to achieve especially for larger pictures.
Phantogram: a popup stereo that appears to be sitting on the surface of the picture.
Popup or Popout: when the image jumps out from the screen. This is OK as long as it doesn't happen around the edges.
Stereogram: Usually the magic eye type of 3D made from dot patterns.
Stereoscope: A device for viewing pairs of pictures without making any effort with the eyes. Usually use parallel picture pairs.

The above terms are as generally used by flickr 3D users. Here is a comprehensive 3D glossary.

Stereogram in wikipedia.
Anaglyph image in wikipedia.
Stereoscopy in wikipedia
Autostereogram in wikipedia (the magic eye type thing).
3D Journal
Introduction to 3D images & 3D movies at 3D Journal
Make 3D photos with any camera at 3D Journal
Software for making 3D pictures at 3D Journal
Stereoscopic 3D Web Ring for more 3D web sites
C3D Stereophotography has books, cards and equipment.