Photographic film is created from thin layers that sit on top of a transparent/translucent plastic base. The number and chemical composition of the layers is then determined by what 'type' of film it is.
Black and white film has a very different set of layers to colour films - as you would expect! But within colour film there are several distinct subsets that were researched and produced by different companies over the past 150 years. Most of them have become extinct but three common types remain. They are known as C-41, ECN-2 and E-6.
I have summarised their main differences below:
| Aspect | C-41 Colour Film | ECN-2 Colour Film | E6 Colour Slide Film |
|---|---|---|---|
| Common Purpose | Commercial, consumer, and professional photography | Motion picture production | Still photography and projection |
| Application | Prints and digital reproduction | Feature films, TV shows, and commercials | Slides and transparencies |
| Colour Balance | Accurate and balanced colours | Optimised for cinematic colour grading and post-production |
Vivid and saturated colours (Velvia) Natural, saturated colour (Ektachrome, Provia) |
| Optimal Processing | C-41 chemicals for standard colour negative processing | ECN-2 chemicals for specialised motion picture processing | E6 chemicals for slide film processing |
| Availability | Widely available for photographers of all levels | Primarily intended for professional motion picture production, but available respooled for stills photography by various vendors and suppliers | Available for still photographers |
What about processing?
It is tempting to see that table and believe that when it comes to developing and processing the films they are entirely separate. However there is a subtlety... the chemistries are similar enough that you can use the different developing processes on each and still get a scannable result!
The practice of processing E6 slide film in C-41 is the most common (usually called XPro or cross-processing) but you could do the same with all the types of colour film.
While this is an entirely valid creative choice 😊 it will not give you the results that the manufacturer designed, and we believe it's important to make your decision with the full information!
C-41 vs ECN-2 processing
I think the debate of creative choice vs manufacturer decision is most clear with E6 and C-41, because if you don't use E6 chemistry then your film will not come out as a slide - it will come out as a negative with large alterations to the colour balance and high contrast. Similarly, processing a C41 negative film in E6 chemistry results in a low contrast positive image, with an orange base!
It is a more subtle discussion on C41 and ECN-2.
The Eastman Color Negative process was first introduced in the 1950s alongside Kodak's first modern motion-picture negative film stock, and was further revised and improved in the mid 1970s to the process that we have today (ECN-2)
Compared to consumer colour negative films (C41) which traditionally were optimised in contrast in order to give perfect colour optical prints on RA4 paper through an enlarger; motion-picture film stocks are optimised at a lower gamma contrast in order to print either directly onto motion-picture positive film for cinema projection, or these days to have the necessary latitude for cinematic scanning and digital post-production.
In order to produce this difference in contrast, the dyes used in motion-picture film are designed to produce correct colour when activated by the lower-activity CD-3 development chemical, as opposed to the higher strength CD-4 chemical which is used to activate the slightly different dye composition of C41 negative film.
Both dye types can be activated to a degree by either development chemical, but each will only be fully and correctly activated by using the matching dye and chemical combination.
There are also subtle differences in the other development steps between the two processes, which run at different temperatures, including addition of stop baths and different bleach composition for ECN-2 which all combine to fully optimising the colour, sharpness and contrast for these films.
What about / what is remjet?
This is a removable jet black carbon layer added onto the base of motion picture film stocks which serves two main purposes.
- Lubricates the mechanism of cine-cameras when running this film through at 24fps or higher, preventing static-electricity build up inside the camera
- Acts as the anti-halation layer in these films - prevents light being reflected back through the film base causing reduction in sharpness and 'blooming' around the highlights (C41 films have an additional dye layer which serves this purpose instead)
The commercial pre-removal of this layer prior to manufacture is what causes the 'red glow' on Cinestill films as there is no additional anti-halation dye present once the remjet is taken away.
In the ECN-2 process, a specific chemical loosens and allows this layer to be removed and washed away by water as the first step of the process before the development baths.
Without the use of a 'pre-bath' of the correct chemical composition for thorough removal of all of this layer before the film hits the development bath, there is the risk of the now liquid carbon layer contaminating and getting embedded in the film emulsion causing irreparable marks and defects to the film, contamination to the chemistry and generally gunking up and damaging the labs film processing equipment
This is why it is vital that ECN-2 film is never processed in a commercial minilab or dip and dunk machine without pre-removal of the remjet layer!
Cinestill and other brands such as dubblefilm and Candido, sell motion-picture film which has had the remjet professionally removed prior to sale - these films can be processed safely in C41 chemistry in a labs film processor, but due to the difference in chemistry mentioned above, the colour and contrast will not be correct compared to the same motion-picture stock processed in its intended ECN-2 chemistry; but remains a creative choice for those that like the altered colour and high contrast this produces.
ECN-2 The SilverPan way
Here at SilverPan, we only use the official Kodak manufactured chemistry intended for use in large custom built commercial motion-picture labs.
We have adapted our technique and small-scale processing machines in novel ways in order to correctly match each of the 10 processing steps to its intended temperature and time, and have tested the results extensively.
It's hard work, very labour-intensive, and something of a labour of love, but we enjoy seeing the results from these excellent films, and hope that you do too!