Technical Pan

Technical Pan was an almost panchromatic black-and-white film produced by Kodak. While it could reproduce the visible light spectrum, it leaned to the red, and so unfiltered outdoor shots would render blues, most notably the sky, with additional darkening and reds with some lightening. These unique characteristics have not been replicated. It was generally used as a very slow film, rated at ASA 25 or even 16, although it could be rated at up to ASA 320 with a distinct loss of tonal range and a bunching of shadow and highlight detail. This film had unmatched fine grain, especially when rated at a low speed, and made excellent enlargements while preserving fine details. Kodak stopped selling it in 2004. It has not been replaced by a film (from any manufacturer) with its exceptional characteristics.

The film could be developed at home, mainly by using the chemical mixture Technidol, which Kodak sold for that purpose alone. Other two bath "split" developers have been used on Tech pan as well as highly dilute developers such as Agfa's Rodinal. To achieve exact results, home development was often the preferred process. Like other panchromatic films, it cannot be developed under any light.

When the film was discontinued, Kodak revealed that none had been made for many years, and that it was still on the market only due to a large roll being found in frozen storage. The film was created for the military and was no longer required for that purpose. Consequently, Kodak cut the roll into commercially viable formats and continued to sell it. Unexposed Technical Pan is now quite valuable and very difficult to find.

Tech Pan, as it is often known, was very popular among some professional photographers and astronomers, as it was capable of recording extremely fine detail, and its sensitivity curve extended much further into the red than most films. In particular, it was very sensitive to light emitted by hydrogen at 656.28 nm (H-alpha), which made it very useful for a wide range of astronomical imaging. Tech Pan was also useful for electron and laser photography. The film was popular with photographers in the art and fashion industries for its extremely high-contrast results when up-rated and processed in an abrasive, high-strength developer.

This description comes from Kodak publication No. P-255, copyright 1985: