The process apparently utilized a sandwich of three glass plates, but I do not know if hand coloring was involved or not.

He had, in fact, developed a system of producing three-part color photographs that could be projected simultaneously. Using a small folding hand camera of the type designed by Mieth, he photographed three exposures of the same subject, made at about one-second intervals on a glass plate approximately 84-88 mm wide and 232 mm long, which was mounted vertically in the camera. The plate dropped to a new position after each exposure, and the image was captured through three different color-separation filters. Because of the need to take the same picture three times, Prokudin-Gorskii was limited to subjects hat would make no movement. Thus, much of what he recorded consisted of fixed objects.

He had also developed a special treatment that hypersensitized the Ilford “red label” plates he was using. After developing, the images could easily supply contact prints, from which excellent color photographs could be made. The remaining problem lay with overcoming the difficulties that arose when the standard projection systems were used in conjunction with his three-part separations.

His unique solution was a projector first developed by F. E. Ives, which he modified so that “from the point of view of rapidity of arrangements and quality it gave better results…” He had it constructed in Germany to his specifications, using three rhomboidal prisms cemented together to make one combination prism. By adjusting the focal lengths and correcting for distortion so that the optical distances became equal, he was able to focus the three colors on the screen precisely.