I'm happy with this formula, which is the inverse ratio of the diagonals: *ird = SQRT( ( 5152 ² + 2904 ² ) / ( 640 ² + 480 ² ) ) = 6.978...*

Then read equivalent focal length

`exiftool -FocalLengthIn35mmFormat filename.jpg`

Focal Length In 35mm Format : 150 mm

calculate *150 * ird = 150 * 6.978... = 1046.80...*

Apply

`exiftool -FocalLengthIn35mmFormat=1046.80 filename.jpg`

Then -FOV (field of view) is updated, and maybe some others.