The Influence of Projection Lamps on the Colors of Early Silent Cinema Films

Quantitative data on the colors of early film productions is very scarce but may be useful for preserving these cultural assets and for guiding modern digitization processes. We measured the spectral transmittance of 46 small areas in 13 frames of films from the 1910s and 1920s, which were colored using the same tinting process. From spectral measurements of the light source in an early carbon arc cinema projector, we computed CIELAB color coordinates for these areas and the results were compared with those from two more recent light sources: a Xenon lamp and an ultra-high performance (UHP) lamp. Average color inconstancy values for the 46 samples were 3.5, 7.9, and 7.0 CIELAB units for carbon-Xenon, carbon-UHP and Xenon-UHP changes, respectively, which are color differences above human visual thresholds for observers with normal color vision. Therefore, for accurate color specifications of such films, in addition to the spectral transmittances of frames, we must consider the spectral power distribution of projection lamps. Compared with a recent surface object-color gamut, the 46 samples were spread across a relatively wide region of color space, excluding CIELAB hue-angles in the range of 270–360 degrees.