本标准规定了镜头标记、焦距公差、安装直径、在镜头上安装额外镜头适配器时的机械因素，以及35毫米和70毫米电影放映机中使用的镜头焦距的首选值步长。（本标准中提到的焦距是等效焦距，通常称为EFL。）本标准还规定了使用不同焦距、设计和附件的投影仪透镜支架的限制或最大可用空间。

This standard specifies the lens markings, focal length tolerances, mounting diameters, mechanical factors in mounting additional lens adapters to lenses, and the preferred value steps in focal lengths for lenses used in 35- and 70-mm motion-picture projectors. (Focal length referred to in this standard is the equivalent focal length, commonly known as EFL.)This standard also specifies the limiting or maximum available space for projector lens mounts where lenses of varying focal lengths and designs and attachments thereto are used.