A smaller aperture means one ray per scene point — sharp, but almost no light. Open it up and each point smears into a disc: brighter, blurrier, drifting back toward the no-barrier smear. Real pinholes also diffract below about 0.3 mm, so the image blurs again; this widget stays geometric.

Shrinking the sensor crops; it does not zoom. Watch the dog's image height in millimetres as you change sensor size: it never moves, because h′ = hf/Z has no sensor term in it. The picture only appears to enlarge because the panel always shows the whole sensor — exactly as a photograph is viewed at one size whatever the camera behind it.