The E-4 process is a now outdated process for developing color reversal (transparency) photographic film.
The process is infamous for its use of the highly toxic reversal agent Tertiary Butyl-Amine Borane (TBAB). The use of the reversal agent permits processing of the film without the manual reexposure that its predecessor E-3 required. The process is also faster and ran at 30°C (85°F, ± .5° F), about 6°C (10°F) higher than E-3. The ME-4 process was a motion picture variation of the E-4 process.
Process E-4 consisted of nine chemicals:
Prehardener, Neutralizer, First Developer, First Stop Bath, Color Developer, Second Stop Bath, Bleach, Fixer, Stabilizer
Total darkness was required during the first four chemicals. Normal room light was used for the remaining five. Temperature tolerance was 1°F for Prehardener, 1/2°F for the two Developers, and 2°F all other steps.
The process was phased out in 1976 with the introduction of the E-6 process which was more environmentally friendly due to its lack of toxic chemicals.
Today the process is discontinued but was used up until 1996 for Kodak IE Color Infrared film. This was due to legal commitment by Kodak to provide the process for 30 years.