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In a photo camera the shutter simply opens and closes like a curtain to expose the film to light. This speed is determined by the shutter speed parameter in the Maxwell camera. It is denoted as fractions of a second - 1/20 for one 20th of a second, 1/40, 1/250 etc. Setting the camera this way means your shutter will be open for a given period of time, no matter the fps setting of your animation time line.
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