标准胶片特性曲线的测试对胶片的选用十分重要，通过该过程，可以得到ISO感光度、ISO平均斜率和ISO斜率G2、G4等参数，这些参数是胶片生产厂家确保产品质量和用户了解产品性能的重要指标。提出标准胶片特性曲线测试的方法，它是以固定的X射线管电压和管电流值、固定的曝光时间值以及均匀的焦距变化值，通过计算得到不同焦距时的射线能量K，从而完成标准胶片特性曲线的测试，并最终得到被测试胶片的感光特性参数。

The measurement of normal film characteristic curve is important to choose film system. By means of this process, we can get ISO speed, ISO average gradient and ISO gradients G2 and G4. These parameters are significant indicator for film manufacturers to ensure product quality and for users to know the product property. The measurement method of normal film characteristic curve is realized by working out ray energy value(units: Gy) through keeping tube current, tube voltage and exposure time fixed and uniformly changing focus-to-film distance. At last, we can get the photographic characteristic parameters of the film.