这位科学家访问了生产照相底板的公司，要求调换这个有缺陷的胶片。
Oblivious to its cause, this scientist called the photography company and ordered a replacement for the "defective" film.
在铅块上方某一距离处放一照相底板。
Some distance above the lead block a photographic plate is placed.
在使用胶片之前，使用的摄影方法是照相底板。
Photographic plates preceded photographic film as a method of photography.
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