Thin-lens equation

The ideal Gaussian thin-lens relation connects focal length, object distance, and image distance.

f is focal length, s is object or focus-plane distance from the lens principal plane, and v is image-plane distance. Solving for v gives the sensor-plane projection distance used by Photivra's focus-aware projection calculations.

Magnification

The magnitude of the ratio describes ideal linear magnification under the same paraxial assumptions.

Model limits

Real lenses can change effective focal length, pupil geometry, principal planes, distortion, and aberrations with focus. The thin-lens model does not attempt to reproduce those lens-specific effects.