Toronto. The earliest photographic processes captured only a monochrome image – usually black and white – of the luminance values of the subject. Over the ensuing decades, many efforts were expended to create natural colour from the effects of light on the subject.
The best ideas imitated the action of the human eye. In 1802, Thomas Young had devised a theory of colour vision later revised by Helmholtz. Most successful ideas to capture colour from nature stem from the application of the Young-Helmholtz theory. Basically, it suggests that the eye has three different kinds of cones each sensitive to a narrow band of the visible spectrum, plus rods which are sensitive to the intensity of light across the visible spectrum.
One such scheme was to use a single lens/shutter and split the light in three, passing the beams through filters to a panchromatic media. This idea resulted in the Curtis cameras which are depicted in this advertisement from the October, 1948 issue of Popular Photography. The registration of three transparencies to create a colour photo was somewhat fussy. Defender offered another solution using its Chromatone process as described in the December 1938 Popular Photography and recorded on the above Curtis cameras link for the reader’s convenience.
A big thanks to my good friend George Dunbar for suggesting the October 1948 advertisement as part of photographic history.