Carbon Arc Film Projection and Technicolor

Submitted by Guest Post,

Today's blog post is authored by Kelsey Eckert, project archivist in the Moving Image Department at the George Eastman Museum. In honor of the 101st birthday of Technicolor, she will be sharing behind-the-scenes stories and insights from the work they are doing to digitize the documents from the early days of the Technicolor Company. Learn more here. 

In their quest to bring natural-looking color to moving images, the Technicolor scientists had to concern themselves not just with dyes and cameras, but with all aspects of filmmaking and exhibition.  One area that they explored was the film projector’s light source.

For the first 60 years or so of motion pictures, film projectors used a light source called carbon arcs.  Film projectors require high illumination to fill any decent-sized screen, and carbon arcs were the only light source bright enough to perform the job.  The light was created by two carbon rods with a small gap between them.  When electricity was made to pass between the rods, the ionization of the air created a very bright “arc” of light.  The bright light was due to the highly luminous nature of carbon vapor. 

The carbon rods needed to be constantly adjusted to maintain a consistent gap between them.  As they burned down, they became shorter and shorter, and the arc would change in size and shape, making the color temperature of the light vary.  An operator would be tasked with keeping the rods at the correct distance. 

The variance in color temperature was less important with black and white film, but for Technicolor, all of these factors needed to be standardized to ensure a consistent presentation.  If the carbon arcs were not carefully monitored, skin tones could end up looking too red, or a sickly green.  Technicolor was constantly under scrutiny in its early days, as critics and audiences were skeptical about the worth of the enterprise, so all efforts were expended to ensure consistent film screenings for audiences and investors alike.  The Technicolor scientists sought to create a carbon-arc system that would require minimal intervention from the projectionist, thus minimizing human error in the presentation of their films.

The Technicolor process of 1916 (sometimes called Technicolor 1) also required significantly more light than a normal film.  The process involved a single light source in the projector that illuminated two frames simultaneously.  For satisfactory results, the light source had to be both incredibly bright and incredibly steady.  Unfortunately, increasing the voltage on the carbon arc for brighter illumination resulted in a wildly unsteady result, with the arc flickering, hissing, and “traveling” around the ends of the carbons. 

The 1916 investigation into carbon arcs included theater visits around Boston, where the company was stationed at the time.  This is one of their sketches of the carbons that they found being used.


Carbon Arc design 

An effort was then undertaken to control the arc through the use of magnetic fields.  A steadier arc would give a steadier illumination to the film.  These experiments sometimes yielded odd results, like this “spiral” arc sketched by Daniel F. Comstock in 1916.


Carbon Arc design closeup 

Though Technicolor never really put these methods into practice, this particular set of documents emphasizes the level of control that the company sought to exert over all aspects of film presentation.  Technicolor as a company could not succeed without this level of rigorous investigation.  The spirit of scientific inquiry and experimentation is evident in all of their research materials.  Technicolor changed and revised its color process many times after 1916, and later processes did not require the high illumination of the early efforts, so the push for brighter and steadier carbon arcs was essentially abandoned.  By 1935, with the introduction of the “glorious” three-color Technicolor process, the films could be shown with normal illumination.

Carbon arc lighting was gradually replaced by xenon lamps, which lasted much longer and did not require the constant supervision of a projectionist.  The xenon lamps were introduced to the US in 1963 and became ubiquitous by the 1970s.  Recently, digital projectors have been introduced which use lasers as a light source, which may become the new standard in the future.

These Technicolor documents and many others will be freely available to view online through our Technicolor Digital Library, launching in July, 2017.


Tuesday, February 7, 2017