3D ADVANTAGE TRI-DELTA BEAMSPLITTER

An alternative way to take digital stereoscopic pictures

3D Advantage with Casio Exlim onboard

The an alternate means to twinning two digital cameras for our digital stereo photography is to use a single camera with a beam-splitter mounted.  This approach ensures synchronisation and with today’s high resolution digital cameras, splitting the image is not a problem.  Beam-splitters were commonplace in the 1950’s and can still be found in the second-hand markets.  The Tri-Delta configuration offers a solution to most of the optical problems experienced with other beam-splitter systems and for this reason, Larry Heyda chose it as the basis for his 3D Advantage product.   

The design of the 3D Advantage is well thought out and assumes the posture of being the dominant part of the total system.  That is to say, the camera is mounted onto the beam-splitter rather than the opposite.  The optical path detour of the Tri-Delta configuration requires the camera to be mounted horizontally with the lens axis perpendicular to the norm.  This being the case, the 3D Advantage has the required appendages for a camera mounted in this way.  An optical right-angle finder views one half (left hand image) of the camera’s LCD display.  Mirrors have been included for the light sensor and built in flash.  Further details include adjustable mirrors providing a variable stereo base.   All of this has been styled into the cast resin housing which includes two hand grips adding stability to the system in use.   Folding panels have the dual purpose of lens hood and protection for the surface coated mirrors.  A shoe is also provided for a slave flash unit. 

My own 3D Advantage was built to take the Casio Z 1200, a 12 mega pixel compact with a 4 x 3 aspect ratio.  The light path of the 3D Advantage is such that two images are captured base to base, each having a 3 x 2 aspect ratio.  This landscape format, similar to that of a 35mm film camera, is an ideal format for View-Magic prints and digital projection.  The camera is secured via the tripod bush and is readily removed for regular 2D use and battery changing etc; the optical viewfinder is hinged to aid camera mounting and removal.  

Rear view showing Viewfinder and Stereo Base adjustment.

In use, operation of the camera’s shutter release is within comfortable reach and the viewfinder image from the well shielded LCD display is very acceptable, even in bright conditions.  Setting the stereo base is aided by a calibrated scale around the mirror adjustment knob that also indicates the near point for the set stereo base.  In most circumstances the stereo base setting may be left at around 2.5” (63mm) but the full range of 1.5” (37mm) to 3.25” (82mm) allows optimal settings for close-ups, portraits and landscapes.  Unfortunately, the lens hood can be problematic cutting off some of the image when the stereo base is set less than 2” (51mm) stereo base, unless it is zoomed out of the field of view with the camera.  The lens hood can also masks the camera flash to some extent, leaving about 10% at the lower edge of the image under exposed when shooting close-ups.  I have not found these faults to be a serious inhibition being apparent only under extreme circumstances.

It is possible to use the 3x optical zoom facility of the Casio Z 1200 with the 3D Advantage and with some experimentation, very acceptable near macro photography can be achieved, well below the near point of 3’9” (1.2 metres) optimum for a 1.5” (37mm) stereo base.   

The images taken with the 3D advantage seen here have been aligned in StereoPhoto Maker.  This program has the ability to import Tri-Delta – base to base (BB) stereo pairs and automatically align them before saving in your preferred format.  The amount of alignment correction required is minimal, reflecting the accuracy to which the system has been manufactured. 

The Powerhouse at Manchester Science Museum

Autumn Patio Display

The 3D Advantage costs less than £500 and fitted with the Casio Z 1200, twelve mega-pixel camera, will compare favourably with a professionally twinned pair of digital compact cameras.  Measuring around 150mm x 150mm x 200mm it is possibly more obtrusive than the latter, but is very reliable and simple to use with less risk of malfunctioning. 

Barry Aldous – August 2008