Eastman Color Negative (ECN) is a photographic processing system created by Kodak in the 1950s for the development of monopack color negative motion picture film stock. It is part of the Eastmancolor family of products sold by Eastman Kodak.
The original process, known as ECN-1, was used from the mid to late-1950s to the early to mid-1970s, and involved development at approximately 25 °C for around 7–9 minutes. Later research enabled faster development and more environmentally friendly 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 Fujifilm 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.
The ECN-2 process has normally been reserved for high volume labs involving hundreds or thousands of feet of film in a linear processor. With companies like QWD that have made this available in a kit form for home use, this process now can be done on a small scale. ECN-2 kits sold to consumers often don't comply with process standards dictated by Kodak[1] and therefore results may significantly vary in quality and consistency.
The ECN-2 process is closely related to the C-41 still picture process. 35mm ECN-2 film can be loaded into 135 cassettes and used in a still camera. It can then either be processed in its native ECN-2 chemistry or cross-processed in C-41 chemistry, although doing so requires that the remjet layer be removed in an ECN-2 prebath. Motion picture camera film has a different sprocket hole perforation shape and pitch than normal 135 film, but it is close enough that it will work in most still cameras. Cross-processing in C-41 chemistry results in a more-dense negative, but with little to no change in color. If the remjet layer is not removed, it can cause damage to the developing equipment and chemicals; therefore, most C-41 labs can't process ECN-2 film.[2] Some companies, such as Cinestill, sell ECN-2 film in 135 cassettes with the remjet layer pre-removed, and these films can be processed at any C-41 lab. ECN-2 film can also be cross-processed in E-6 slide film chemistry, which produces a positive image with a purple cast. As with C-41 cross-processing, this requires removal of the remjet layer.