Starting a Minimum ECN-2 DIY Developer kit.

Randy Stewart · Nov 3, 2024

hamoodhabibi said:
The development of CD-4 and C-41, I believe, is intended for stable automated operation under large batch sizes, a shorter development time, at a more friendly temperature. However using the ECN-2 process to process films intended for C-41 actually renders acceptable results (but given that CD-4 is more active than CD-3, you have to use 1.3x the original development time when using CD-3 to process C-41 film (p.s. that's why Cinestill packs 5219 500T at ISO 800 and 5207 250D at ISO 400 lol))

In the meantime, after some investigation, I can say that the main difference of C-41 and ECN-2 is the developer (CD-4 vs CD-3). Everything else is more or less similar, could be just differences in amounts each chemical is added. Tetenal/Arista(Cinestill) acutally share the blix in their C-41 and ECN-2 kits.

For a DIY color positive kit, there is an open source formula for E-4, and the openly available Kodak E-6 patent as the basis. This forum actually have guides on how to make a DIY kit following the E-6 patent. However, several caveats exist:
1. both E-4 and E-6 have some additives not easily sourced in public (Hydroquionine is even one of the easier chemicals to get);
2. The fogging agent is also not easy to find. If we decide not to use chemical fogging agents, like what we have in E-4, then after the first developer we will want to expose the films in the air to fog the film.

1. The higher film speeds assigned to Vision 3 film by Cinestill and some others is not based on use of CD-3 or Cd-4. It results from uncontrolled flare introduced by removal of the remjet anti-halation before exposure. Of course, this is not a true speed increase, but just additional, non-image density.

2. ECN-2 developer (official formula published by Kodak) calls for use of CD-3, not CD-4. (Same as for C-41.)

3. The E-6 reversal technique used as an alternative to chemical reversal is exposure to light, not to air, although to do so commonly requires exposure to air incidentally. Light exposure reversal was the standard technique used in "E" processes prior to E-6. Chemical reversal was adopted with E-6 to enable production of more efficient and hands-off commercial slide processing equipment. The in-house E-6 process used by Kodak to test production standards for E-6 film still calls for light reversal, according to an obscure publication.

lamerko · Nov 3, 2024

Normal processing in standard C-41 chemistry of unmodified ECN-2 remjet film will result in higher density and contrast than in its standard chemistry. Cine film stock and their chemistry are designed for low contrast. Conversely, still photography films and their C-41 chemistry are intended for higher contrast. The developing agent CD-4 in C-41 is much more active than CD-3, which is used in ECN-2 and E-6. Removing the remjet can slightly increase the density through the "backlight", but at the same time the contrast will drop due to light scattering.
Chemical reversal has been around long before E-6. For example, Kodak's official document for E-4 (CIS-111) has "KODAK Reversal Agent RA-1" in the formulas - this is tert-Butylamine borane (TBAB) - an extremely toxic chemical and was abandoned after some scandal. Subsequently, a substitute was found that was not so dangerous and is present in E-6 now.

koraks · Nov 3, 2024

Randy Stewart said:
It results from uncontrolled flare

I don't think so. You have a source for that statement?
It seems more plausible to me that it's due to the higher gamma that results from cross processing ECN2 film in C41 developer, which can be regarded as a means of pushing the film. It helps that Vision3 films are rated conservatively.
I don't think the flare story has anything to do with it, as the halation effects resulting from a lack of remjet are very local.

Starting a Minimum ECN-2 DIY Developer kit.

Randy Stewart

lamerko

koraks

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