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Lighting and Speed of Seeing

Nature volume 142, page 789 (29 October 1938) | Download Citation



A BECENT article (Brit. Eng. Export J., September) describes practical advances that have recently taken place in lighting. An interesting experiment is described which shows a relation between illumination and the speed of vision. The apparatus used was a heavy pendulum on which a test object was exposed to view when swinging between two screens. The speed of movement of the object was directly proportional to its distance from the pivot. At high illuminations, the test object could be seen when it was placed at the lowest point of the pendulum. At intensities not exceeding two foot candles, it was only visible when it was placed at a distance not exceeding a quarter of the way down, when its speed is only a quarter of what it is at the lowest point. After an increase to five foot candles the speed of seeing was increased by about 60 per cent.

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