Finally getting around to documenting the small bit of circuitry in the project to make it easier for folks  to produce.  And as am added bonus, I get to learn KiCad!  KiCad is a really great, free, open-source schematic and PCB layout tool.

The circuit board facilitates the connections between the hardware elements in the system.  Those elements include the external shutter trigger on the PiCameras, the GPIO interfaces on the Pi computers, and the switching for the strobe light.  Importantly, the connection board opto-isolates and provides separate ground planes for each subsystem, including the higher-voltage strobe power supply.  That turned out to be important after I accidentally killed two different Pi units due to what appeared to be voltage transients from the strobe power supply getting to the GPIO chip on the Pi's.  Now, each power supply area is a separate, hopefully-safe island of its own.

Shout out to the H11 high-speed opto-coupler chip.  Very easy to use, and quite hardy.

Now if I can just find a low-cost, low-volume PCB manufacturer...

Follow-up:  I'm trying JLCPCB, a low-cost China PCB factory.  They were pretty easy to work with.  I just uploaded my Gerber files and their website produced a quote and showed me a 3-D version of my board in a flash.

I hope to go from this mess of spaghetti:

To (hopefully) this: