Quote - Yup - assuming you're basing your focal length on a 35mm camera equivalent, as most photographers still do even when using a camera with a different sensor size - Poser's cameras' focal lengths are 0.7x that.  In other words, to get a field of view similar to a 35mm film camera with a 50mm lens, set your Poser camera to 50 x 0.7 = 35mm focal length.

Citation: Bagginsbill says so here and here, and elsewhere too. ;)

(I have reason to believe the exact value might be the reciprocal of root 2).

Poser is a very old program. Parts of it were written when Edward II ruled over England. But Edward II did not know about meters; he measured things in inches, feet, and yards. Therefore there are imperial units are scattered around in poser all over the place. The virtual camera is no exception. It uses a virtual film size of exactly one inch (which is 25.4 mm in metric units). So if one is accustomed to small format cameras (which use the 35mm film and an actual image size of 24x36mm), one needs to get that factor into account to get the same field of view. That factor (36mm/25.4mm) is 1.417323 which is very close to 1.4142 (the square root of 2), although not exactly the same. Not that this would matter much when one uses only Poser, the difference is only 0.3%; but cannot be neglected when one wants to do pixel exact composition of a poser render with a render of a different graphics program (but there are other factors which make life even harder...)