photomatch - translating a compact digital camera into vray physical camera

[rikou]

thank you stef ! a bit confusing but now, It's all right !

[plastic_]

I wouldn't take the focal length specs with cameras too seriously.
Even with professional lenses there is a different FOV between to similar focal lengths. For example, a 70-200mm lens at 200mm may actually be 180mm, compared to a 200mm prime lens, even if both are canon lenses.
With compact cameras there is also additional cropping going on because of the barrel distortion correction.
The only real way to find out the true focal lenght for footage, is calculating it with software like syntheyes or boujou.
Otherwise it will be at least +-10mm off, you may aswell guess the values by eye, this would give a better result.

[stef.thomas]

Yeah, and just wait till you try photomatching a panorama too! Actually VRay RT is a godsend when it comes to that, giving you real-time camera distortion in the viewport.