What is critical illumination?

Critical illumination is a term used in photography and lighting design. It refers to the minimum amount of light needed to properly expose a subject or scene. If the light is too dim, the subject will be too dark or underexposed, while too much light can cause overexposure and loss of details. Critical illumination is essential for achieving accurate and balanced lighting and ensuring that the photographer or designer captures the details and essence of the subject. In architectural lighting design, critical illumination also refers to the minimum amount of light required for safety and visibility in a space.