The original process, known as ECN-1, was used from the 1950s to the mid-1970s, and involved development at approximately 25°C for around 7–9 minutes. Later research enabled faster development and environmentally friendlier film and process (and thus quicker photo lab turnaround time).
This process allowed a higher development temperature of 41.1°C for around three minutes. This new environmentally friendly development process is known as ECN-2. It is the standard development process for all modern motion picture color negative developing, including Fuji and other non-Kodak film manufacturers. All film stocks are specifically created for a particular development process, thus ECN-1 film could not be put into an ECN-2 development bath since the designs are incompatible.