In Houdini 10 the camera object has a default focal length of 50 (mm) and a default aperture of 41.2136 (same units). Is there anything special about these values? In earlier versions of Houdini the aperture defaulted to 41.4214 which, when combined with the 50mm focal length, results in a field of view of exactly 45 degrees. Now, with an aperture of 41.2136, the resulting field of view is 44.7967 degrees. Is there any particular reason for this change? Is an aperture of 41.2136 special for another reason?

The documentation at http://www.sidefx.com/docs/houdini10.0/ref/cameralenses [sidefx.com] seems to suggest that I should be changing the focal length (rather than the aperture) to reverse-engineer a particular field of view, but I'm wondering why SideFX suggest that this is preferable to changing the aperture instead (or both together, for that matter).

Or does it really not matter at all, as these two values are combined by the renderer to compute the field of view and then discarded? If so, would it not make sense to simply provide the user with a single field of view parameter (in degrees) and dispense with the focal length and aperture parameters?

YBM