A smartphone camera module has a 4 mm focal length lens at
PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Geometrical optics and imaging · Geometrical optics and imaging
What an Instrument Can See, Ch Pupils: the aperture of a linear system
Problem
A smartphone camera module has a 4 mm focal length lens at f/1.8. The chief ray to the corner of the image sensor leaves the exit pupil at a field angle of 35∘. The manufacturer's measured relative illumination at that corner is 0.35 of the centre value.
((a)) Estimate how much of the corner darkening is accounted for by the cosine-fourth law alone.
((b)) Estimate the vignetting factor and state, in one sentence, whether corner darkening in this module is mostly a vignetting effect or mostly a cosine-fourth effect.