Don't Break the Window

Stereo 3D photography requires a different approach to composition and framing than traditional two dimensional photography. Generally, the best subjects are those that have natural depth that will be highlighted by the stereo effect. However, the 3D photographer must always be aware of the stereo window and take care not to break the stereo window.

When you look at a two dimensional image, you are looking at the scene. With a 3D image, you are looking into the scene as if you were looking through a window. The edges of the image form the boundaries of that stereo window. Just like a real window, there can be things to see through the window and there can be things to see in front of the window. But if there is something at the left or right edges that projects forward, the stereo window is violated and the stereo effect no longer works.

This 3D image of an Orchid has a severe window violation.

In the stereo pair it is easier to see how the green bud on the right breaks the stereo window.

These images of orchids from the St. Paul Winter Carnival are examples of severe window violations. The green bud on the right is placed significantly in front of the viewing window but violates the window by projecting beyond the right edge. There is a significant difference between the left and right views at that edge which is confusing to the eyes and prevents a good 3D effect. There is also a window violation on the left with the yellow flower.

This 3D image of an orchid has good depth and no window violations.

In the stereo pair, you can see that no part of the orchid crosses the stereo window.

You can avoid window violations by framing scenes to keep anything that is closer than your primary subject away from the left and right edges of the image. Generally, this means shooting scenes at a wider angle than you might for a 2D image. The second set of orchid images show good 3D depth without any window violations.

Have you tried capturing any 3D images yet?  If so, please share the links.

How to View Stereo 3D Content

Stereoscopic 3D imaging provides depth to pictures by simulating the different views seen by each eye. While the concept is as old as photography, it has gained an unprecedented amount of support in the last two years from the entertainment and consumer electronics industry. A growing number of major movies are being filmed in 3D, major video games are being released in 3D, all major TV and monitor manufacturers are making 3D TVs and Nintendo has released a 3D version of their hand held game console. All of these are potential viewing devices for 3D images.

All stereoscopic 3D images, whether still or video, consist of two separate views in which elements are positioned differently depending on how deep they are in the scene. Viewing a stereoscopic 3D image requires a method to allow each eye to see only one of the two images. Here are the most common methods for viewing stereoscopic content:

Parallel View – Parallel view consists of placing the left and right images side-by-side on a monitor or printed card. While some users are able to fuse the two images into a single 3D image on their own, most require a viewer to help focus each eye on the correct image. One of the simplest and most effective is the Loreo Pixi viewer which consists of two prisms mounted in a folding cardboard glasses frame. Using the Loreo viewer,  any computer monitor can be used to display 3D content.

The Loreo Pixi 3D Viewer

Red/Cyan Anaglyph – An anaglyph image applies a red cast to one view and a cyan cast to the other. Glasses with red and cyan lenses filter the views for each eye. This is one of the easiest and cheapest methods because the images can be displayed on any device and cardboard red/cyan glasses can be purchased in bulk for about $.50. However, the quality is poor. The method distorts the color of the image and there is frequently ghosting because the filters in the glasses do not match the display color. 

Anaglyph image of a bird in flight.

Passive Sequenced – The 3D movies currently shown at theaters use the passive sequenced method where the left and right images are projected one at a time in rapid sequence through filters polarized at opposing angles. The viewer wears glasses with polarized lenses to filter the images to each eye. This viewing method is also used with some consumer level 3D projectors.

Passive Interlaced – The passive interlaced method requires building the polarized filters into a TV monitor in strips. The right and left images are interlaced into the strips and the viewer wears polarized glasses to filter the images to each eye. This method is being used by some high end 3D TVs, but it adds significant cost to the production of the TV. As the costs come down, this may become the preferred technology for 3D in the living room because the glasses are inexpensive and do not require charging.

Toshiba Laptop with Active Shutter Glasses

Active Shutter Sequenced – Most of the 3D TVs that are in the stores currently use the active shutter sequenced method. The right and left images are shown in rapid sequence and the user wears a pair of glasses with LCD shutters which turn on and off in sync with the screen refresh on the TV monitor. This is the least expensive technology right now for the home because it does not require significant changes or additional costs for the monitor. The disadvantage, particularly in households with children, is the need for keeping the batteries in the glasses charged and the replacement costs if the glasses get lost or broken.

The Nintendo 3DS uses a parallax barrier to show 3D content.

Parallax Barrier – The Nintendo 3DS hand held gaming console, the display on the Fuji 3D camera and a number of recently announced 3D laptop computers have parallax barrier screens. With this method, the left and right images are interlaced onto an LCD screen. A second LCD screen layer creates a series of lines which keep each eye from seeing the images intended for the other eye. This approach is autostereoscopic which means that it works without any type of 3D glasses. However, the user has to be at a particular distance from the screen and at a particular angle to experience the 3D effect which limits its application to small, single-user devices.

Lenticular – Lenticular printing is not really a stereoscopic display method but instead mimics the effect of stereoscopic viewing. For lenticular printing, typically 12 to 24 images are interlaced into a single print which is laminated onto a special lens to allow the viewer to see different views as the image is rotated. To create a lenticular print from the left and right views of a stereoscopic 3D image, special software must be used to create the intermediate views.

Although there are many ways to view 3D content, I usually post images as a 3D stereo pair and a red/cyan anaglyph. This makes them accessible to readers with the least expensive viewing tools. 

How do you prefer to watch 3D content?

Stereoscopic 3D Basics

Replica of traditional stereo viewer from 3D Concepts

I enjoy taking 3D pictures and watching 3D movies. There have been several posts here which either comment on 3D content or include 3D images. In this post, I would like to explain the basic concepts behind 3D photography and 3D cinematography.

Each of us have two eyes approximately 6 centimeters apart. When both eyes are functioning properly, we see two slightly different scenes in each eye. Our mind combines those scenes and uses the difference between them to determine depth.  

To see how this works, slide back until you are about three feet from your computer screen and hold one finger up about halfway between your face and the screen. Now close one eye and note which words are still visible. Now open your eye, close the other and note which words are visible. At short distances, the difference between the scenes captured by each eye is quite significant.

As our minds process the differences between the two scenes, there are two pieces of information that are used to determine depth.  The first, horizontal parallax, is the difference between the relative positions of items in the two scenes. In our example, we know the finger is closer than the screen because it moves right and left on the screen as we switch from eye to eye.

Note the differences in which people are visible in the backgrounds of the two frames of this stereoscopic 3D image of street performers at Santa Monica pier. The difference in who is hidden is called occlusion revelation. The difference in the relative positions of the tourists is the horizontal parallax.

The second clue to depth is called occlusion revelation. This refers to the small areas of a scene that are occluded or hidden from one eye but revealed to the other. The perception of those small areas and the width of those occluded areas are a major input in our brain’s calculation of depth.

When we view a traditional 2D photography or movie, we can still recognize the depth of the scene through several monoscopic cues. We can make depth judgements based on perspective, the relative size of objects, changes in texture gradients and position relative to the horizon. Occlusion is also the most important monoscopic depth cue because any object that hides must be in front of what is hidden.

3D photography increases the level of realism by adding back in the stereoscopic depth cues. This is done by showing each eye its own unique view of the scene. Stereoscopic 3D requires a way to capture or create the scene with separate right and left eye views and a way to present each of two those views to the appropriate eye. I will explore those methods in future posts.

The stereoscopic 3D image above was captured with this Loreo 3D lens adapter which uses two focusing lenses to project two separate image views onto one camera frame.

What is your favorite 3D movie so far?

DC in 3D

When I was a child, I had a Viewmaster with an Americana disc.  While exploring Washington DC this weekend with a 3D camera, those memories came back vividly.  I hope you enjoy these stereo pairs and anaglyph 3D images from our nation's capitol.

Washington Circle

 

Washington Monument

Jefferson Memorial

Lantern and Jefferson Memorial

Jefferson Memorial

 

Terri in Smithsonian Garden

Magnolia Blossoms

Roosevelt Memorial

Lincoln Memorial from Arlington National Cemetery

Arlington National Cemetery

All images Copyright 2011 David Williams

QR in 3D

I have been having fun with QR codes, stereo pairs and anaglyph 3D as a form of modern art.

Enjoy!

          
                                                                    Self Portrait #1

                                                                  Self Portrait #2

                                                                  Self Portrait #3

                                                                  Self Portrait #4