Authors of Tang Song Ci are fond of using the images of curtains in their poems because they are influenced by the aesthetic standard at that time, the scholar\'s "feminization" mentality and the stylistic function of"writing for singing".

In order to meet the demand for a film-space camera with large aperture to take photograph,a type of focal plane-curtain shutter is designed,which utilizes the movement of front-curtain and back-curtain to form a narrow slit, and then makes the film exposure.