Samuel Morse was astonished to learn that Daguerrotypes of streets of Paris did not show any humans, until he realized that due to the long exposure times all moving objects became invisible.

美国发明家萨缪尔·摩尔斯看到用达盖尔照相法拍的巴黎街景里一个人都没有时，不禁大吃一惊，后来才明白是因为曝光时间过长，移动物体都变得看不见了。

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