A deeper dive into CineStill Simplified Cs2 chemistry: ECN-2 + CINESTILL = ? 

We are the Brothers Wright, the photographers and creators behind CineStill. Ever since the beta tests of CineStill 800T processed in C-41 chemistry, and especially once we began designing simplified chemical processes, we have been asked many technical questions about motion picture processing and still photography.

Over the years, we have done our best to point people in the right direction, but some of the mythology on the internet has perpetuated regarding motion picture film. From flawed processes to poorly executed “side-by-side” tests, many misconceived notions have prevailed in regards to both the process and the film. Often times the questionable results are a byproduct of a poorly produced positive rather than the negative itself.

Since we have access to all of the resources in the industry to perform the practical testing and produce the sensitometric data for every variation of the process, we recognize the pitfalls and reasons why many have had a bad experience trying to unlock motion picture technology.

In the interests of definitively demystify the most common controversies which remain mere conjecture on the internet, we decided to perform another series of tests and share them here with you via EMULSIVE. In this article, you will find data, examples and comparisons of CineStill and Kodak VISION3 motion picture films developed in CineStill’s existing Cs41Color Simplified C-41 kit, our brand new Cs2 Cine Simplified ECN-2 kit, and native ECN-2 chemistry.

Here’s what we cover:

Let’s start with an important and often asked question:

CineStill originally released Cs41 Color Simplified C-41 Kits. why not ECN-2?

We need to get a bit technical here. The motion picture process involves a specific mechanical and chemical process for motion picture labs to produce long lengths of motion picture negatives, which print consistently on ECP-2 print film for projection. C-41 processing was designed for darkrooms and mini-labs alike, for printing on RA-4 color paper.

Although the formulations have varied slightly between manufacturers (whether it be Kodak C-41, CineStill Cs41, Fuji CN-16, Konica CNK-4, AGFA AP-70, etc.), it is by far the most accessible color film process. Proper ECN-2 processing requires special laboratory equipment and additional safety measures that can’t be attained at home.

We only release quality products that we believe in and can back up. Successfully processing film with all of the troublesome ECN-2 steps, or at a motion picture lab, still results in a much thinner, flatter contrast negative, ideal for the motion picture workflow. C-41 chemistry produces a denser, more dynamic negative with greater tonal range and color separation for printing accurately on RA-4 color paper and scanning. We are bridging the gap between motion picture and still photography, making motion picture technology accessible and compatible with still photography processes.

Above left: Photo by Henry J Keith on CineStill 800T processed with Cs2 Cine Simplified.
Above right: Photo by The Brothers Wright on Kodak Portra 400 processed with Cs2 Cine Simplified.

Motion picture processing machines use caustic chemicals that you don’t want in your home, such as sodium hydroxide (lye) and sulfuric acid (battery acid), which can cause chemical burns from handling. In addition to PPE, industrial exhaust vents are needed to carry away dangerous vapors and provide for the safety of the lab operator.

Emulsion acts like a sponge and carries color developer into the acidic color stop bath, generating poisonous hydrogen sulfide and sulfur dioxide fumes. Heat and any acid added to the ferricyanide bleach can liberate highly toxic cyanide gas, along with the forming of Prussian Blue deposits on film, reels and tanks.

Simply bypassing the hazardous color stop bath and going into the ECN-2 bleach will oxidize the color developer remaining in the emulsion, and cause severe staining to the film. Safer B&W stop baths (e.g., citric or acetic acid) introduce byproducts that cause leuco-cyan dye problems in the red-sensitive emulsion layer (i.e., green images) and interfere with the bleaching step. Additionally, bleach carryover into the separate fixer causes the film to be mottled with smears of color.

This is why the ECN-2 process also specifies Solution Crossover Devices with multi-stage countercurrent washes between steps. If you are going to follow the ECN-2 Specifications for Processing KODAK Motion Picture Films you must use all of the proper equipment as well.

Above: RA-4 darkroom prints.
Left: Cs41 processed CineStill 800T, 8 second RA-4 print, with zero color correction.
Right: Cs2 processed Kodak VISION3 500T 5219, 1 second RA-4 print, heavily corrected for red and yellow.

When designing CineStill Simplified Cs2 chemistry we didn’t simply repackage the published Eastman Color Negative chemical formulas for at-home use, because chemical recipes are only one aspect of the ECN-2 process.

After years of research & development with motion picture chemistry, we believe we have formulated the only safe and consistent way to process stills with the same characteristics Hollywood expects, from the comfort of your home with the Cs2 “Cine Simplified” ECN 2-Bath Kit.

Why does Hollywood still use ECN-2? I heard that it was more advanced technology…

ECN-2 chemistry is not any more advanced than C-41. In fact, the color developing agent used in ECN-2 (CD-3) is the predecessor to the advent of C-41 (CD-4). Our new Cs2 formula is actually more advanced than either, utilizing chemical compounds and technology which didn’t exist before, resulting in an improved safer process.

ECN-2 and C-41 processes were originally formulated back in the mid-1970s with the available technology of the day, to produce negatives for different purposes. Large scale ECN-2 processing was designed to produce consistent, thin negatives for quick printing on high contrast ECP-2 film with short exposure duration, to save time and money. Denser C-41 negatives could take up to 8x as long to print or scan, and time is money when printing 24 frames per second.

Above: Left, Developed negatives (unconverted).
Right, converted using CineStill Film Conversion Filters.

The more advanced technology is found in the VISION3 emulsions used in Hollywood and CineStill films, whichever way they are processed. The primary difference between C-41 and ECN-2 negatives is the contrast curves produced in development, not the color quality or the size of the halides. Despite misinformation found around the internet, there is no incompatibility between the silver halides and dye couplers. The developing agent reduces any exposed silver halides in emulsion into metallic silver, oxidizing the dye couplers incorporated within each layer to produce color images. The dye couplers are in the emulsion not the chemistry, so you can’t mismatch halides and couplers, because they are already matched in the coatings.

Motion picture film technology has advanced by leaps and bounds through the improved emulsions, even though the process hasn’t changed in 40+ years.

Above: No correction RA-4 contact print exposure test, 1-32 sec.
From left to right: CineStill 800T with Cs41, Kodak VISION3 500T 5219 with Cs41, Kodak VISION3 500T 5219 with ECN-2 Kit, 5219 with Cs2 Kit, Kodak VISION3 500T 5219 machine processed ECN-2 by FotoKem Motion Picture Lab.

Some of this advanced motion picture technology has even been handed down to still photography films like Portra 400. Whatever emulsion you use, any film processed with ECN-2 or Cs2 will exhibit much lower color contrast and muddy whites and blacks when printed on RA-4 color paper.

Conversely, films processed in Cs41 have too high of contrast and density range to be compatible with ECP-2 motion picture printing. When it comes to making a photograph, cross-printing is more of an issue than what some would call “cross-processing”.

Isn’t processing CineStill color film with C-41 chemistry technically cross-processing?

That’s like saying that processing Kodak Tri-X with T-MAX developer is a cross-process, or using any developer other than D96 for BwXX (Kodak EASTMAN Double-X 5222) is cross-processing. Traditionally, cross-processing is processing one type of film through a process intended to produce a different type of film (e.g. negative film as a positive and vice-versa, or color as B&W), not simply using different solutions intended to produce the same type of processed film.

If you have color negative film and you process it to be a color negative it’s not really a cross-process. Alternative formulations can be used for each process to successfully produce the same film type with different characteristics, just like with black and white film. Although each process type is designed specifically for a film type (i.e. B&W, color, negative, reversal, etc.), more importantly, each process is designed for a specific presentation output.

Below: Photos by Henry J Keith on CineStill Film processed with Cs2 Cine Simplified.
Click to view in full screen

Just as motion picture printing and presentation requires a negative with different characteristics from C-41 processed negatives, still photography color negatives should be processed with a CD-4 developing agent (C-41, Cs41, CN-16, etc.) to be compatible with RA-4 photographic printing and photo lab scanners. 

This is because ECN-2 negatives have an optical density range of around 1.6 (6 stops), while C-41 film is about 2.2 (8 stops), inherent of the process rather than the emulsion itself. This equals up to a 30%+ increase in tonal and contrast range. The target contrast gamma of the Cs41 process is between .6 to .65, but ECN-2 film is only .45 to .55.

Below: photos by Koltin Sullivan of Lauren Lākin & Henry J Keith on CineStill 50D processed in Cs41 (top) and Cs2 Cine Simplified (bottom). Grab and drag the slider to compare.

Basically, ECN-2 processed negatives are thinner and flatter, and aren’t ideal for the analog photography workflow. Even if you adjust the processing time to get a denser (pushed) ECN-2 negative there will still not be enough of an increase in contrast or color separation to match the curves of a C-41 negative, since it also lifts the base density of the film (especially with formulas omitting the proper antifoggant). This has been observed for many decades now, and we actually had to repair this bad reputation among photographers, who mistakenly assumed that our color films would turn out thin and flat looking, even when processing C-41 as intended.

The color developing step controls the contrast curves but leaves the dynamic range of the negative unaffected because the density range is increased with the contrast. The limit to dynamic range would only be in the cross-printing but not when scanning. Color developer pH and temperature shifts color from colder to warmer, because as it increases (from 102-106ºF) so does the depth and activity of the developer on the lower green and red-sensitive layers. The Cs2 process is warmer than the Cs41 process, and it also yields a warmer color temperature. Color temperature and density can easily be corrected in printing but contrast cannot.

Above: 21-step Sensitometric Characteristic Curves.
Top left: CineStill 800T with Cs41, Top right: CineStill 800T with Cs2, Bottom left: CineStill 800T with Cs41 vs Cs2 neutral density curves, Bottom right: Kodak’s target curves for 5219 match CineStill 800T with Cs2.

The CineStill Simplified Cs2 process can perfectly match the published sensitometric curves for a motion picture negative, designed to be accurately printed as a positive on ECP-2 film or log scanned as a digital intermediate for color grading.

Developing CineStill color films in Cs41 chemistry as intended yields contrast curves, color separation and density range that compliments chromogenic printing and scanning for still imaging, making it easier to make beautiful photographs.

I’m not printing my negatives in the darkroom. What does it matter if we are scanning our film?

You can always scan any type of film, processed by any method you prefer. You can’t however go back and make an ECN-2 negative into a C-41 negative for printing, or vice versa. Both can be scanned with a density range suited for the respective process, but ECN-2 negatives require added contrast and care. Cs2 processed film will exhibit a more flat, linear curve, whereas Cs41 will render a higher contrast S-curve with more color separation.

The characteristic curves produced by each process are designed to match the target densities for printing. The Cs2 process is great for extremely high-contrast scenes or to achieve that “flat cinematic look”. A lower density range (below 2) logarithmic scan of a Cs2 processed negative and further color grading is recommended to create a pleasing still photograph.

Above: Fuji Frontier mini-lab scans.
Left: Corrected Cs41 Processed CineStill 800T. Center: uncorrected ECN-2 (top) & C-41 (bottom) negatives cut in half.
Right: Corrected Cs2 processed Kodak VISION3 500T 5219.

Even when scanning, the narrower density range of ECN-2 negatives can limit control and how much bit depth is utilized within the wider dynamic range of the digital sensor. Film scanners have a range of density from 3 to 4, to capture the optical density range of positive films from about 3.2 to 3.6. This means that a 14 or 16bit linear raw scan could need more than half of the information to be clipped, resulting in a less than 8bit image after adding the necessary contrast. Negative film is very forgiving, but the process of creating a positive is not so much.

Then why not just process motion picture film with Cs41?

Rem-jet backed motion picture film was designed for continuous machine processing and will contaminate any C-41 chemistry. Even with an added alkaline prebath step, the rem-jet adhesive wax will not be fully dissolved without mechanical or manual removal. This black carbon silt will not only contaminate your developer, but also your tank, reels, precious film and everything else it touches. If you don’t like dust, you are going to hate rem-jet on your film.

Do not drop off motion picture film at a photo lab! Standard motion picture film will contaminate other customers’ film, and chemistry tanks in the processors. Rem-jet can be removed in a motion picture lab machine or manually removed under running water after hand development in Cs2. Bleach/blix or stop bath will re-adhere rem-jet to the film, but it can still be manually removed after processing by hand. Due to the presence of residual backing material and the chemical by-products it liberates, one shot processing is recommended. Do not process rem-jet backed films in the same solutions with other films.

If rem-jet removal is attempted prior to development, by soaking film in a borax or baking/washing soda bath (at pH ~10) and washing the rem-jet off by hand under running water, it must be done in complete darkness. Attempting rem-jet removal manually in the dark may result in insufficient removal, damage to the emulsion and premature exhaustion of developer. A rewash may be necessary to fully remove rem-jet backing after processing.

Above: Camera scans with Skier Sunray Box and corrected with Negative Lab Pro.
Left: CineStill 800T processed Cs41, Right: Kodak VISON3 500T 5219 processed Cs2 with rem-jet removed manually.

The rem-jet is designed to be removed prior to processing. CineStill films are coated with Kodak Vision3 motion picture emulsions, but have undergone our proprietary “premoval” process which converts it to be safe and compatible with mini-lab, pro-lab or at-home processing, while preserving the inherent motion picture qualities. CineStill films do not require rem-jet removal and are perfectly safe to process in any color chemistry with other films.

Would I be better off just trusting in standard photo lab processing and CineStill Film?

It would seem so. After all, professional photo labs do the best job when it comes to processing and scanning film. On the other hand, who are we to argue with do-it-yourself ingenuity? For those of you who wish to dabble in the motion picture workflow we have formulated some original at-home solutions, designed to match Eastman Kodak sensitometric standards for motion picture film. Whether you prefer the more saturated look of Cs41 or the flatter contrast of Cs2, we are here to support more opportunities to shoot film in more environments, to not only keep film alive but to stimulate its renaissance.

The Cs2 “Cine Simplified” Kit simplifies the original 10+ step ECN-2 process to only 2 chemical baths, with uncompromised quality and accurate characteristic curves, while making it safe and foolproof for at-home use. Our Cn2 “COLOR NEGATIVE” developer is combined with the prebath accelerant (which kicks off development) to produce proper ECN-2 density.

The bleach and fixer baths are combined with the stop and wash baths in our single Bf2 “BLEACH&FIX+STOP” bath, to reduce risks to health & safety and processing defects caused from chemical carryover. After a final washing of your film you will have CineStill negatives matching Kodak’s characteristic curves for proper motion picture processing. It may be a less complicated process than ECN-2, but Cs2 is actually more advanced chemistry, formulated with components that didn’t exist when ECN-2 was originally designed.

Even though it is simplified and safer, we didn’t skip or compromise any of the designed functions of the ECN-2 process. Whether it be with the color developing agents or the combined baths, we don’t settle for incomplete formulas that omit essential active components (e.g. Antifoggant to prevent base-fog buildup, Anti-Calcium to prevent precipitate and contamination, Ammonium Thiosulfate to fully clear silver and dyes, Development Stop to prevent color staining, etc).

Proper ECN-2 negatives. No compromises. No BS. We’ve got you covered.

~ Brian & Brandon Wright