All the buzz about the movie Avatar has me reminiscing about the Optics issue of MAKE. In Volume 14, award-winning filmmaker and digital artist Eric Kurland showed us how to build a 3D dual-camera rig, and make a live 3D video monitor and PSP stereoscope to go with it. Here’s Eric’s intro and backstory, and at the end a link to the project shared with you in our Digital Edition. You can also still pick up a physical copy of Volume 14 to add to your collection over in the Maker Shed.
Homebrew Digital 3D Movies
Build your own stereo video camera and 3D viewer.
By Eric Kurland
I have two eyes. And because of that simple fact, I also have stereopsis, the ability to perceive depth. When I was about 7 years old, I gazed into a View-Master toy and saw an amazing three-dimensional picture, and I was hooked. Today, I create 3D videos, using various homebrew camera rigs and displays. I’ll introduce you to a few of my devices, but first, a quick history lesson.
In 1838, British scientist and inventor Sir Charles Wheatstone theorized that seeing with two eyes together is what allows us to see in 3D. Wheatstone deduced that each eye observes a slightly different view of the world, and our brain fuses these two perspectives together, interpreting the parallax differences as depth. He called his discovery stereoscopic vision (literally meaning “to see solid”) and built an optical device, the stereoscope, that allowed three-dimensional viewing of pairs of drawings.
With the invention of photography, and later cinema, real-life images could be captured with two lenses and viewed in 3D. The popularity of stereoscopy has persisted over the years. In the 1890s, arcades offered 3D peep shows as entertainment, and the handheld stereoscope was a common item in home parlors — the TV of the Victorian era. The 1950s and 1980s both saw 3D movie “booms” come and go, due to the technical limitations of the times. And currently, in the age of digital video, stereoscopic 3D is seeing a major rebirth.
My own foray into 3D video began a few years ago, after I attended the monthly meeting of the Stereo Club of Southern California. Many of the photographers at the meeting had pairs of digital still cameras mounted side by side for shooting 3D photos, and it occurred to me that I could build a similar hand-held rig for use with small camcorders.
Shooting 3D
Starting with a pair of Sony Handycams, I set out to build a stereoscopic rig. My plan was to make the distance between the lenses, called the interaxial, equal to my interocular, or the distance between my eyes. This would give a natural-looking 3D depth to my footage, and would allow me to view 3D while shooting, just by looking through both camera’s viewfinders. Putting the lenses so close required removing the hand strap from the left camera.
I attached the cameras to a metal bar using quick-release mounts for easy removal, in order to access the tape and battery compartments. I fashioned a bracket from some spare parts to hold both cameras securely at the top and keep the lenses aligned. Inspired by director Mike Figgis’ steering wheel-like camera stabilizer (the “Fig Rig”), I bolted together a pair of photographic flash bars with handgrips, salvaged from a flea market dollar bin, and created a “handlebar” stabilizer. This allows me full mobility with the rig, and puts the center of rotation between the two cameras.
To control recording, I use a device called the 3D LANC Master. Developed by Dr. Damir Vrancic of Slovenia, the 3DLM connects the cameras via the LANC ports and provides simultaneous control of most camera functions. It also keeps the video recording in sync by continuously polling the timing frequency of one camera, and adjusting the frequency of the other up or down to prevent drift. This is very important when shooting 3D, as any time disparity between the camcorders will result in nonmatching left and right views. Schematics and software for the 3DLM are open source under a GPL and are available for free.
Viewing Live 3D
With my camera setup complete, my next task was to build a portable stereoscopic video monitor, so others could watch live 3D during shooting. In movie theaters, stereopsis is achieved by projecting left and right images through two oppositely oriented polarizing filters onto a reflective screen. By viewing through 3D glasses made from matching polarizers, each eye sees only the corresponding projection. I decided to use the same principle for my monitor.
I started with two small LCD monitors capable of showing NTSC video, the kind that are strapped to the back of car headrests. The video output from each camera is input to one of these monitors. Because LCDs have a polarizing layer, these displays appear black to one eye and visible to the other when viewed through polarized 3D glasses. I found that the monitors had a clear plastic protective sheet glued over each LCD. These had to be carefully peeled up and removed, as they were depolarizing the light from the screens.
On one display I needed to flip the picture horizontally like a mirror image, so I opened the case and wired pin 62 of the PVI-1004C LCD controller chip to ground. I attached the LCD displays to each other at a 90° angle, their screens facing inward, and mounted a piece of half-mirrored glass between them. This glass superimposes the reflection of one screen on top of the other. When viewed through polarized glasses, the reflected image and its polarization are reversed, each eye sees only one screen, and we have live 3D video of whatever is being shot.
Editing 3D
Shooting with two cameras creates two individual video files, which are digitized into the computer for editing. First, I use the freeware application StereoMovie Maker, developed in Japan by Masuji Suto, to correct misalignments in my footage, which can cause eyestrain.
In StereoMovie Maker, I am able to load both the left and right videos and visually transform, scale, and rotate them while viewing in 3D with anaglyph glasses. Anaglyph is the method in which the two pictures are combined into a single image with one eye in red and the other in cyan. Primarily used in printed stereoscopy, anaglyph also provides a means of viewing depth on any computer screen using inexpensive red-cyan glasses.
Once satisfied with the alignment, I save my videos as a single file, formatted side-by-side in a split screen, and twice as wide as a normal video picture. I prefer this format, as it ensures that the two views always remain in sync throughout the editing process. The footage can be cut together in any standard video editing program. My system is PC-based, so I use Adobe Premiere, but the same techniques would apply to a Mac Final Cut Pro system. One thing to take into account when editing 3D is that drastic depth changes between consecutive shots can cause eyestrain.
To watch my completed movies in 3D, I use Peter Wimmer’s excellent Stereoscopic Player program, a full-featured media player for stereo video files that converts on-the-fly to the many different viewing formats required by stereoscopic displays and projectors. Both Stereoscopic Player and StereoMovie Maker are Windows-only applications, but they will run on Intel Macs running Windows.
Showing 3D
In order to show 3D video to audiences, I have a dual-projector setup, just like the 3D theaters of the 1950s, using two projectors, polarizers, and a silver screen. The only real difference is that my projectors are small DLP digital models, and my “film” is a file played back by computer. This arrangement works well for large audiences, but I also wanted some method of carrying my 3D movies with me to show at a moment’s notice — a portable stereoscopic media player.
The Sony PSP looked like it would be the answer. The PSP can play MPEG-4 files from a flash memory card and it has a nice, wide screen — wide enough to hold side-by-side-formatted left and right images.
In fact, the PSP is just about the same size as a standard vintage stereo card. I decided it would be cool, and somewhat steampunk, to mount a PSP onto a circa-1904 stereoscope.
As luck would have it, the PSP fit almost perfectly between the two card-holder wire clips. I didn’t want to physically alter the viewer, as it’s an antique, and I wanted the PSP to be removable, so I cut two loops of thin velcro strapping, just long enough to go around the PSP and hold it firmly to the slide bar.
To get my videos onto the PSP, I converted them to x264 compressed MPEG-4 files at the PSP’s screen resolution of 480×272 pixels, and copied them to a PSP Memory Stick. Sure enough, side-by-side video files played on the PSP and viewed through the stereoscope’s eyepiece are seen as a single three-dimensional movie.
The whole setup works perfectly. I can easily carry around a bunch of my homemade 3D movies on a Memory Stick in my pocket, and quickly show them to people through the “PSPscope” — a perfect marriage of 19th- and 21st-century technologies.
Check out the full project in our Digital Edition.
ADVERTISEMENT
