This calculator computes one of the following:
- animal (for example bird) or other photographed object size
- focal length of the lens
- distance from the camera to the photographed object
(or rather object distance)
- camera sensor or film frame size
- photographed object image size : camera sensor or film frame size ratio
- spotting scope magnification (if used)
from the remaining parameters. It is not applicable for fisheye lenses.