Tracing of 20mm in length implies that 1 mm corresponds to 1 second.
Coincidence even in half a millimeter implies coincidence in the synchronization in half millisecond or less.
To get more precision we would need a laser with a narrower trace, but it would not be easy to adapt a surgical laser to this test.
I do not think that it is necessary to be more precise in the Barry Aldous test because synchronization of half a millisecond or less, I think it is enough to obtain synchronized 3D photos in our current circumstances.
Timo and Randy, I've never used flash on the A6000 Sony rig with the VMC-MM2 cable. In fact instead, I use 2 pieces (thumb-grips) to increase the ergonomics of the cameras.
Dan, I've observed that operating the shutter on the main camera the sync es perfect but operating the shuter on the sub-camara (the cam conected to the L-shaped plug, right angled) it's not possible shoot the main camera and only one pic (in the sub-cam) is obtained. Also using the DSLRKIT (female + male plugs) you do not need external shutter. The Sony VMC -MM2 cable is available in different countries with differents prices:
https://savemoney.es/asin/Sony%20VMC-MM2
Thank you Georgios. Thanks Path. I'm really enjoying a lot the 3D Sony Alpha rig (A6000 + VMC-MM2 cable+ A6000), almost every weekend. :-)
I tried a flash test with my a5100 pair. Using the built-in pop up flash both cameras flashed when the flash units were up. However the exposure from the two cameras did not match. The right camera (master) had good exposure but the left was over exposed. It appears that the left "saw" both flashes but only metered for one. With one one flash "up" it was even worse. The non-flash camera metered for no flash and then was very washed out as a result of the flash.
Have you tried using a flash with this rig. Perfect synchronization would suggest "yes", at least with a dumb flash. But what about with a TTL flash? 2 TTL flashes?