It is cool... I like gizmos thanks for sharing.
I was just stating a photographic maxim, I have always known, and most of also know that few gizmos other than a light tight box and focusing lens are needed.
Way back in the day there were "light meters" that used some photo-sensitve paper and a timer, to judge the intensity of light to make a more accurate exposure. They were neat little brass and ivory cylinder things with the light sensitive paper inside.