!Restored: view cone angle vs. camera lens focal length

[Anonymous]

I'm trying to align an ac camera view with a photo of the site (set as the 3d window background); the ac align view function is not useful in this specific context as there are no adjacent existing (vertical) elements to use as references. I've been able to get the view relatively aligned manually, but have found the main variable that is affecting the accuracy is the view cone setting; so:

the photo information says it was taken at a 28mm focal length; how does this relate to the view cone figure? that is, what would be the conversion factor?

[Dwight]

But lens angle isn't only the focal length or the proportion - it also relates to the size of the sensor.

[Fran_ois Chatelain]

Hi Dwight,
which is why it's important to check the EXIF data of any digital photo, which conveys all (most of) the necessary information to help you make the adequate conversion, that is multiply the focal length by the crop factor.
Once you know the camera make and model, as well as the focal length used for the photo, it's quite easy to do the maths to get the real focal length.
It can prove a tad more fiddly if the photo was shot with a P&S camera 😉
But hey, do as I say but not as I do since I always eyeball my alignments in EIAS. That is until I go blind...
Cheers
Francois

[Dwight]

Since you are vastly my better at this imaging stuff, I'm glad that we agree that the eyeball is better than blind focallengthanglecropproportion calculations for establishing camera aspects.

A few minutes spent gently walking a model into place is the best way i know of for matching backgrounds.