1935 ad for an orthochromatic film called Plenachrome by the maker
Toronto. One of the earliest ambitions of film makers was to expand their film’s sensitivity spectrum down to the reds. By the mid 1930s when Agfa-Ansco made this film, yellows, greens through near violet blues could be captured. Such a film was known as orthochromatic by the industry. Agfa chose to use the term “Plenachrome” and to tout the film as ‘ideal’ for outdoor subjects. It was actually just too slow for use indoors or at night. It faithfully reproduced most of the colours of nature.
Five years later, Agfa-Ansco advertised a panchromatic film finally capable of recording oranges and reds too. While the Plenachrome film was sold in 100 foot and 50 foot rolls of 16mm size, 35mm film was similar in sensitivity. Agfa sold this movie version with processing included in either straight negative or reversible (positive, ready to project after processing) options. The films of the era were mostly monochromatic black and white films.
My thanks to our retired corporate photographer, George Dunbar, whose talents range from stills to videos. George shared this tasty bit of history with me which he found in the March, 1935 issue of American Cinematographer magazine.
The more expensive panchromatic films were slow to take off, especially in still format since the processing had to be done in a fully darkened room by the time-temperature method after very accurate exposure. Orthochromatic film was cheaper and could be developed and viewed by a dim red light allowing the development time and/or temperature to be adjusted to help compensate for any exposure error. Savvy photographers used yellow or green filters of various density on the camera lens to modify the film’s H-D curve (eg. show both clouds and sky).
NB. The name of this post is a line from Shakespeare’s play Romeo and Juliette.
