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* 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 or something else.
*soon only to be available in two flavours -  DAZ and Renderosity