Prizma Color’s two-color additive process was a short-lived, stop-gap process that arrived in late-1917. It was a bridge between the Prizma’s four-colour additive process and the later subtractive Prizma process. It used the same negatives as Prizma’s four-colour additive process, but changed the projection method from using color projection filters to alternate dyes on the film print. As a transitory process, the imperfection of Prizma’s two-color additive process was clear in both the technology and the results on-screen. However, by eliminating the color projection filter, Prizma’s two-color additive process brought the inventor William Van Doren Kelley’s vision for natural color films one step closer, by adding the color to the film print so it could be projected using the same equipment as used for standard B/W films, only at a higher speed of 32 fps.

After the theatrical debut of Prizma’s four-colour additive process on February 25, 1917, at the Strand Theatre in New York City, the drawbacks of the four-color additive process became noticeable. The high projection rate of 32 fps caused the perforations to break with an alarming frequency, which interfered with the required perfect synchronization of the film and the color projection filters. This damage, caused by high projection speeds, also reduced the life of the film print to about one-third of its normal life (Moving Picture World, 1919; Kelley, 1919). Soon after, Kelley’s collaborator and one of the founders of the Prizma Inc., Charles Raleigh, left the company, as he doubted the additive method would ultimately prove successful in achieving natural color on film (Crespinel, 1929).

As an inventor, and a technically minded person, Kelley remained committed to the additive method and quickly made progress in eliminating many of the drawbacks of Prizma’s four-color additive process. The first key step towards that goal was the development of the method known as the alternate-dye method. It was a means of obtaining color results without the need for the color projection filter attachment required by the earlier process. The positive prints were alternately dyed red and green, frame after frame – effectively applying the color projection filters directly onto the film print itself. The projector, however, still needed to run at 32 fps to obtain the illusion of color on screen as a result of the persistence of vision. Although Kelley regarded this system as far from perfect, it was a step in the right direction in comparison to Prizma’s existing four-color additive process. 

The first public performance of the new process came with the premiere of the feature film Our Navy (1917), plus several short subjects, on December 23, 1917, at the 44th Street Theatre, New York City. According to contemporary reports, the whites of the subjects were sparkling clear, an indication that the color dyes used were complementary to one another – at least, very nearly so. Pure greens and yellows, however, were still unobtainable, as noted by Motion Picture News (Cory, 1918). The screen result, remembered many years later by Leopold Godowsky, Jr. (co-inventor of Kodachrome), had poor definition, was artificial and very unsatisfactory – additionally it was a difficult and cumbersome process to operate (Godowsky, 1971).

Despite the imperfections of Prizma’s two-color additive process, Our Navy was screened around the country during 1918 and, from the second half of the year, also in edited versions of various lengths, renamed as Our Invincible Navy ( Motion Picture News, 1918a; Motion Picture News, 1918c). During this time of war, the film was praised for its educational content and patriotic nature, rather than its technical achievements. It was also shown at the White House, Washington, DC, on February 11, 1918 (Motion Picture News, 1918b).

It is hard to know precisely the number of film prints made using the alternate dye method, given the challenging nature of the dyeing process. Local screening reports of Our Navy indicate that some screenings still used color projection filters rather than alternate-dyed frame prints (Washington Post, 1918). One article advertising the film to theatre managers stated that, “if you could afford the slight re-arrangement of your projection machinery, necessary for the showing of Prizma natural color pictures, … ‘Our Invincible Navy’ is a splendid four-reel subject as an added feature attraction.” (Motion Picture News, 1918c). 

Another explanation for the limited use of the Prizma’s two-color additive process might be the temporary departure of Kelley from Prizma Inc. during 1918, who left to pursue experiments with the subtractive Kesdacolor process. By the end of 1918, Kelley had returned to Prizma Inc. with yet another improved version of the Prizma process launched in early 1919, now employing double-coated positive film, which finally made Prizma Color films compatible with standard B/W projection equipment, at a standard projection speed.