I see you've made both vFov and hFov, that's great.
But it would be really nice to have a 35 mm equivalent focal length too.

I know it can be a bit tricky if the photo/video is not 3:2, but since Sitrec already calculates the HFOV from the imported image/video, I think the equivalent focal length should be based on the horizontal FOV.
This would also make sense for cameras like my Canon R8, where switching from a 3:2 photo to 16:9 video crops the top and bottom. The HFOV remains the same, so the 35mm equivalent should remain the same as well.

Done!

It's a little fiddly, so let me know if there's any problems.

Damn you're quick!
It looks like it working fine. I just wonder how I can unlock the aspect ratio if I want the look view different that the video/photo - but maybe it doesn't make sense to do that.