Okay, just completed another test for the Main Camera using the diagonal stripes (similar procedure to what I did for the dollycam).

This test appears to confirm the results from the previous post, i.e. 12.7mm seems to be the correct focal length for the main camera to get a 90° FOV, and the DollyZ value required to place the camera at the origin is now a bit more precise -113.5" (±0.05").

Here's the almost perfect match I got using DollyZ = -113.5":

Here's the mismatch with DollyZ 0.1" less:

And here's the mismatch with DollyZ 0.1" higher:

I also checked the joins between other adjacent pairs of 90° renders (if you consider the above test was the join between the north/east facing renders, I also checked the east/south, south/west, and north/up joins using the same diagonal stripes - almost perfect match in all cases with 12.7mm and -113.5")

Still not 100% proof positive, but getting closer. Once again I'd appreciate it if anybody can see any errors in my logic...

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The 3Dcheapskate (also available in DAZ and HiveWire3D flavours) occasionally posts sensible stuff. Usually by accident.
And it usually uses Poser 11, with units set to inches. Except when it's using Poser 6 or PP2014, or when its units are set to PNU.