Originally Posted by MIN_Roadkill
When you set these rigs up are the cameras parallel or do they cross paths at a set point, and if so, how do you determine the point of intersection?
Mostly what Wolfgang said is what I do with a few differences that he and I differ on.
My goal was not to just build a SBS rig but also a design that was simple and light weight for travel, not just by commercial airlines but also to back pack on mountain hikes.
My first design was patterned after the system built by Frank the Thread starter using set screws for alignment. The system used standard Aluminum extruded stock metal and was a chore to fabricate in my limited shop. It also was difficult to calibrate. Long before Wolfgang built his, I also made a second version that used ball heads same as his. While these were faster than the setscrews, the adjustment was just too coarse, added over 2 pounds of weight to the system, required calibration with every setup and raised the center of gravity for the cameras making it less stable in moderate to strong wind I experience on my high altitude locations. Then Frank designed his adding the dove tail quick releases from Manfrotto. He used the heavier ones but I went lighter for previous mentioned reasons. Both worked and taking extra time in the shop to calibrate the base of the quick release to the igus slide table using brass shims in a permanent mount ( but could also be dismantled if needed) I was able to achieve the present design that locked the system so I never needed to align and calibrate the vertical tilt and cross section rotation in the field again. I calibrate once and then it stays. The horizontal rotation as set by the position of the little foot that mounts to the camcorder 1/4-20 hole does need to be aligned with each setup, if you remove it. It stays aligned even for a week of shooting. To avoid even this alignment task in the field, I have semi permanently mounted that foot to all my cameras so everything adapts to every support, whether the monopod, a single tripod, SBS rig. The only camcorder I don't have one for is the Panasonic 3D1.
The igus system
I use is the smaller one from the referenced one that Woolfgang referenced. Mine is about half the weight and works strong enough for the weight of the TD10's
To aid in the alignment of setting the two cameras parallel, I turn on the grid lines in the LCD screen. Both the TD10 and the NEX5n have them as an option in the menu.
Then I set the rig up in my shop and aim at a set of calibration distances I have on my wall. There is a center line with distances marked off from center. If the IA is set for 20" then I use the marks 10" left and right from center. The horizontal level and position should be perfect if the construction alignment was done with the shims properly. To get the cameras adjusted the only change is to twist the camera in respect to the little foot mounted on the bottom. This only needs a little nudging normally as eyeballing the mounting of it is actually pretty accurate. In the field, I would verify the calibration by setting the system up and zoom in on a distant object that I can use for reference, such as a building roof line that has known level and plumb lines in the design. Here, I just have to verify that the field assembly has not knocked things out along the way. To date, never have I had to recalibrate as the alignment has remained. So, I now describe this as just a safety check.
I briefly experimented with trying to converge the center points of the cameras on distant objects but found there was no real advantage to this exercise that was tedious and time consuming for no better results. Plus that would need changing with each shot. Parallel works and works for every shot distance.
Here you can see a part of the brass shim sticking out between the igus slide table and the quick release base that was used to tilt the left camera up angle to match the position of the right camera( not shown). Once calibrated these shims do not need changing, ever.