In the early 1900’s photography was dominated by black and white, and color was uncommon to see in use anywhere.

Most color processes involved taking multiple separate color filtered photos on B&W film, which resulted in long exposure times, and hard to align images. Kodak wanted to improve this process and allow standard B&W single frame cameras to take color images without any special modifications.

Kodak engineer John Capstaff began working on a two-color subtractive process that could be loaded into the camera as a “bi-pack”, two emulsion layers that could be loaded into a single film holder together. In 1915 he released Kodak’s first color film, dubbed Kodakchrome though it bears only passing relationship with the Kodakchrome many of us know and remember.

This early Kodakchrome consisted of two sheets of emulsion on glass plates, one that was panchromatic (sensitive to all colors) and another that was orthochromatic (only sensitive to blue/green). The back of the ortho plate was coated red and placed into the bi-pack first, with the emulsion side aimed towards the lens. The panchromatic plate was then filtered by the red coating on the back of the ortho layer, resulting in a blue/green filtered image on the first plate, and a red filtered image on the back plate.

After shooting, the two plates would be separated and developed as positives, dyed blue and red, and recombined to form a color slide. Since only two of the three primary colors were used in this bi-pack, color reproduction did not cover the full spectrum, though surprisingly lifelike results could be had.