Читать книгу Magic Shadows. The Story of the Origin of Motion Pictures онлайн

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Porta also had an explanation of the persistence of vision, so far as it was then understood. As an example, he mentioned that after walking in the bright sun it is difficult to discern objects in the darkness, until our eyes become accustomed to the change—and then we can see clearly in the dim light. To see the natural colors, Porta proposed the use of a concave mirror as the screen for the camera images. He then discussed phenomena resulting from the principal focus of the mirror. He tried to use the parallel to show how we see things rightside up instead of upside down. But his knowledge was not sufficient for that purpose, for he held that the seat of vision was at the center of the eye, as the focus of a concave mirror or lens system. In this he was not correct, according to modern experiments, but at least it was a plausible theory.

As a third point in his description of uses of the natural camera Porta said, “Anyone not knowing how to draw can outline the form of any object through the means of a stylus.” Here was Alberti’s camera lucida, or the camera adopted for the use of painters and designers. Porta instructed his readers to learn the colors of the object and then when it was thrown on the screen it would be easy to trace and paint in natural colors. He pointed out another interesting and important fact—a candle or lamp could be used as the light source instead of the sun.