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modern day Film in the late 19th century

Toronto. The energy of light depends on its wavelength. The higher (shorter) the wavelength, the more energetic the light. Visible light runs the gamut from reds to deep blues and purples. The beginnings of photography used media barely sensitive to blue light and totally insensitive to reds.

In fact, Jim Maxwell’s famous 1861 tri-colour photo of a tartan ribbon would have failed miserably except that the ribbon he chose used a red dye with a strong second harmonic placing all light reflected from the red dye in the sensitive range for wet plate emulsions. The use of a red filter gave a “red” result for this harmonic (if harmonics are not familiar to you, check out Fournier analysis). Throughout the 18th century, media remained insensitive to red light. The common red light for darkrooms was a result.

By the end of the end of the 18th century, Hermann Vogel discovered that adding certain dyes to the emulsion could extend the sensitive spectrum, first to green, then to orange, and later to red.  By about 1906, glass plates were offered commercially with the wider spectrum, but at a far higher cost – and their use demanded total darkness during development.

As a result, it was many decades before panchromatic film became the standard for B&W film. The exception was movie film where the higher cost was offset by far better results – especially in skin tones and sky shots. Minicams used mainly orthochromatic film which gave rise to the wide range of green and yellow filters. When it became available, infrared film prompted deep red filters. Of course polarizing filters would eliminate any specular reflections.

After the second world war, the proliferation of colour film ended any market for the old orthochromatic media.

NB, the title of this post is from a song of the same name published in 1935. This version was sung by the Platters.