James Clerk Maxwell’s Mystery

The Maxwell-Sutton photograph of a tartan ribbon is considered the first permanent color image ever captured. Maxwell displayed the image as a set of overlaid projections of grayscale images which were captured and displayed through red, green and blue filters. The 3 original transparencies still exist, along with a fourth transparency captured through a yellow filter that Maxwell did not use in his presentation.

The frequently displayed reproduction above was actually produced in 1940 in a effort to better understand the scientific and technical origins of color photography. The reproduction drew attention to the fact that photographic chemicals available in 1861 were completely insensitive to the low-energy photons of red light--and yet the photo clearly shows red. Sutton's documentation of his process shows he found it easiest to capture an image through a blue filter, which corresponds to the maximum sensitivity of his chemicals. He found he needed a much longer exposure with his green filter, corresponding to the lower sensitivity of the chemicals. He reported that the red image required less exposure time than did the green. The 1940 researchers found another clue in that the red image is slightly out of focus, despite the care taken by Sutton as he used his red-sensitive eyes to focus the red image.

Let us know how you think an image taken in bright sunlight through a red filter can show shades of red--when the chemicals were NOT sensitive to red photons.

Let us know too if you have ideas for other "Questions Worth Considering" as ways to better connect science, technology, engineering, art and may.