硒光电池（如照相机曝光计中的）。
Selenium cell ( eg the exposure meter of a camera )
结果：通过星卡曝光&微密度计扫描的方法，测试得到了随着空间频率的增加而逐渐减小的屏-片系统的MTF曲线，曲线随着空间频率的变化而连续变化。
Results : The screen / film system MTF curve that decreases continuously with spatial frequency can be obtained by this new method .
曝光计曝光计曝光计