我们在进行照片复制过程中，经常发现复制的胸部片有这样一种现象：于胸部横隔影下方有３条纵向带状影，宽均７ｍｍ，间隔６０ｍｍ，呈平行排列，其密度较淡，比横隔密度略低。而观察母片则正常。其它部位的复制片观察不到这一现象。技术人员对此众说纷纭，难以解释清楚。... During the process of photo copying, we often found that there was such a phenomenon in the replicated chest films: there were three longitudinal banded films under the shadow of the chest transverse, 7mm in width and 60mm in width, arranged in parallel with a lighter density, Slightly lower than the transverse density. The observation of the mother is normal. Copies of other parts of the observed this phenomenon. Technicians are divided on this, it is difficult to explain clearly. ...