Complex sentence: Keller-Dorian cinematography was French technique from the 1920s for filming movies in color, using a lenticular process to separate red, green and blue colors and record them on a single frame of black-and-white film.
Split into simpler sentences: Keller-Dorian cinematography was French technique from the 1920s for filming movies in color. It used a lenticular process to separate red, green and blue colors and record them on a single frame of black-and-white film.