"When a lens intended for a larger sensor is used on a smaller sensor camera, the projected image circle does not fully cover the sensor area, causing vignetting or black corners in the image."
- Axis Lens Guide White Paper
"Black corners or vignetting often result from a mismatch between lens and sensor size."
- Axis Communications Academy, Network Video Fundamentals, 2022
References:
Axis Lens Guide White Paper
Axis Communications Academy, Network Video Fundamentals, 2022 (p. 34)