ˈbi-pack
[bi-2.]
In colour photography, a pack of two sensitive plates or films used to obtain colour separation.
| 1924 Brit. Jrnl. Photogr. Suppl., Sept. 35/2 The staining of the front member of a bi-pack with aniline orange. 1935 Discovery July 192/1 Using two films in the form known as ‘bi-pack’. |