VRayPhysicalCamera film gate vs standard Max aperture width

[jksim]

Hi all,
We've got a pretty standard lens-matching approach for live action footage with standard max cameras which works well - set the aperture width in the render dialog to the film back width/sensor width, plug in the lens focal length, and bam, perfect match (well, pretty close depending on distortion).

I'm having a problem achieving the same result with the PhysCam... in this case the footage is shot on an Arri Alexa (sensor width is 23.76mm) and a 40mm max standard camera matches with the live plates shot at 40mm with 23.76mm aperture width. To get the same FOV/framing with PhysCam, I have to change the lens to 31.431mm (FOV 33.083, same as the max camera)

Am I missing something? Has anyone had any luck matching real world lenses (in this case a Cooke s4) to the VRayPhysicalCamera?

We are still in 2010, but using VRay 2.25.01

cheers,
Josh

[Morne]

just use your standard camera, then use Lele's script to convert the standard cam to physical cam

[jksim]

Thanks Morne, though I was really hoping that there may be a technique where I could actually plug the 40mm focal length value into the PhysCam and get an accurate result. Seems odd that a camera that is meant to be physically accurate doesn't work with such fundamental values. Again, I'm probably doing something wrong, but if anyone has a solution or an explanation that doesn't involve a workaround, I'd be keen to hear it.

thanks
Josh