Canon’s Thorpe Shares Lessons in Live 3D Capture
The array of technology used for stereoscopic 3D capture has come a long way in the past two years, but a handful of technological barriers continue to plague 3D film and television production teams. At SMPTE’s International 3D Conference last week in New York, Canon National Marketing Executive Larry Thorpe outlined these fundamental issues and the efforts currently underway to correct them.
“We learned the hard way, as have so many practitioners, that 3D is difficult – especially live 3D,” said Thorpe. “It is fraught with all kinds of optomechanical perils. We certainly got a lesson – along with Sony – at the [2010 FIFA World Cup last summer], where we learned these boundaries very quickly.”
First Order Errors: Optical Mis-centering in Lens and Camera
The foremost concerns involve the fundamental tolerances of lenses and cameras and the issues that are created when you marry the two for 3D production. A slight irregularity in the lens, camera, or beam-splitting prism can make for serious mis-centering issues that degrade the quality of the 3D image.
“[We’ve gained] a tremendous wealth of knowledge over the past few years – most of it bad news regarding some fundamental issues related to marrying a lens to a camera,” said Thorpe. “The real nemesis to 3D acquisition is the fundamental built-in tolerances of any lens and any camera and the marriage of the two. In a single-camera and single-lens 2D world these [tolerances] are very tiny, but in a 3D world you’re exposed. The tiny differentials are seen and certain shots can be very troublesome.”
While motorized 3D rigs have eliminated a large bulk of these “first order errors,” many 3D crews still find themselves spending hours upon hours fiddling with the lens-camera-rig configuration to account for any irregularities.
“This is an area that we are working on to try and find a solution,” Thorpe acknowledged. “But as of this moment in time I’m not aware of anybody solving this problem.”
Second Order Errors: 3D Mis-tracking Between Dual Lenses
Thorpe and company have had more success in developing solutions for “second order errors,” which deal with the potential mis-tracking between a 3D lens pair that can cause focus, zoom, and iris to misalign.
Rather than putting expensive R&D into developing “perfect” lenses for stereoscopic 3D, Canon elected to link two standard 2D lenses through a single electronic zoom/focus controller that simultaneously controls both lenses. This allows rental houses and production houses with high lens inventories to utilize the same lenses for 2D and 3D production.
“Rather than trying to make the lenses themselves more precise – that would only elevate costs and our lenses are already too costly – we wanted to work with standard lenses and do something electronically to compensate for the dynamic misbehaviors of the lenses,” said Thorpe.
In order to accomplish this Canon loaded custom 3D software into a microcomputer within the lenses’ digital drive units. The two drive units are linked by a single bridge cable, automatically synchronizing zoom, focus, and iris. This automation can be set up quickly and easily through the display menu.
The underlying technology that enables this dual lens tracking system is a new digital drive unit that incorporates Canon’s ultra-compact precision rotary encoders (capable of 0.1 um position detection), which feature Micro Roofmirror Array (MRA) technology. The MRA technology inside the encoders provides 16-bit resolution of the positions of the zoom, iris, and focus controls.
Microfilms to the Rescue for Mis-centering
During his presentation, Thorpe also highlighted a potential solution to the mis-centering issue discussed earlier. Developed by French outfit Microfilms, the solution utilizes the optical image stabilization system in the Canon HJ15x8.5B portable HD lens. Microfilms employs the system’s ability to horizontally and vertically move the optical image at very high speed to automatically correct optical mis-centering in an integrated 3D rig.
The motorized Microfilms 3D rigs can use any HD camera-lens combination from any manufacturer. The system features three central processor units (CPUs) – two dedicated to managing all of the data for the two lenses and a third for the main microcomputer that receives and sends data to the other two.
“They were demonstrating it at NAB and it was spectacularly successful and worked beautifully,” said Thorpe. “The limitation of course is that it’s one lens. 15×8.5 is not going to do all 3D. But it’s an indication that different people are working towards different solutions for this problem.”