> Focus it on a dark spot, and the camera is inactive. It only knows how to calibrate itself against lightness to define the image.
I don't know much about photography, but AFAIK, modern cameras need contrast to calibrate themselves, not lightness (or darkness). Point the camera towards a dark corner, nothing. Point it towards the sun, nothing. Point it towards a sharp edge of a shadow, or any other high-contrast area, an voila, focus!
I don't know much about photography, but AFAIK, modern cameras need contrast to calibrate themselves, not lightness (or darkness). Point the camera towards a dark corner, nothing. Point it towards the sun, nothing. Point it towards a sharp edge of a shadow, or any other high-contrast area, an voila, focus!