Film Processing Glossary
When you drop off a roll of film at a lab, the "process" printed on the canister tells the lab which chemistry to use. Different processes produce fundamentally different results — color negatives, slides, or black & white prints. Here’s what each one means, where it came from, and why it matters.
Current Processes
C-41
What it is: The standard process for developing color negative film — the most common type of film sold today. When a lab says they process "color film," they almost always mean C-41. The negatives come out with an orange-brown tint (the "orange mask"), which is corrected during scanning or printing to produce the final image.
How it works: The film passes through a color developer, bleach, and fixer at a tightly controlled 37.8°C (100°F). The developer creates metallic silver and colored dyes simultaneously. The bleach then removes the silver, leaving only the dye image behind. The entire process takes about 3 minutes and 15 seconds for the developer step alone, with the full wet process completing in roughly 12–14 minutes.
History: Introduced by Kodak in 1972, C-41 replaced the older C-22 process. It was a major breakthrough because it standardized color negative processing — for the first time, any lab anywhere could process any manufacturer’s color negative film using the same chemistry. This standardization made the one-hour photo minilab possible in the 1980s and is a big reason color film became dominant over black & white for consumer use.
Temperature tolerance: ±0.15°C. Push/pull processing is possible by extending or shortening the first developer time.
E-6
What it is: The standard process for developing color reversal (slide) film. Unlike C-41, E-6 produces a positive image — what you see on the film is what the scene looked like, with correct colors and brightness. The resulting transparencies can be projected directly or viewed on a light table.
How it works: E-6 is more complex than C-41, with six chemical baths. After a black & white first developer creates a silver negative image, the film is chemically "fogged" (reversed) so that the remaining unexposed silver halide is developed in a color developer. This second development creates the positive dye image. The silver is then bleached away, leaving only colored dyes. The first developer runs at 38°C for 6 minutes.
History: Kodak introduced E-6 in 1976, replacing the more toxic E-4 process. It became the professional standard for commercial, fashion, and nature photography because the positive transparency was the gold standard for color accuracy — art directors could hold it up to a light and see exactly what would appear in print. Slide film dominated professional work from the late 1970s through the early 2000s. Today only a handful of E-6 films remain in production, but the process is still available at most professional labs.
Temperature tolerance: ±0.3°C. Push processing is common (up to +2 stops); pull processing is possible but rarely done. More sensitive to temperature variations than C-41.
Standard B&W
What it is: The process for developing traditional black & white negative film. Unlike C-41 and E-6 which are rigidly standardized, B&W processing is a family of compatible approaches — photographers choose from dozens of developer formulas, each producing subtly different grain, contrast, and tonal characteristics. This is the process that makes darkroom work possible.
How it works: The film is immersed in a developer solution that converts exposed silver halide crystals into metallic silver, creating the negative image. A stop bath halts development, and a fixer dissolves the remaining unexposed silver halide so it can be washed away. What remains is pure metallic silver suspended in gelatin — an inherently archival image that can last centuries. Development times, temperatures, and agitation patterns all vary by developer choice and desired results.
History: Black & white development is the oldest photographic process still in regular use, with roots going back to the 1880s when gelatin silver emulsions replaced wet-plate collodion. The fundamental chemistry hasn’t changed much since then. In the 1940s–50s, Kodak’s D-76 became the de facto standard developer, and it’s still one of the most popular today. The process is simple enough to do at home with minimal equipment — a changing bag, a developing tank, and three bottles of chemicals — which is why B&W home developing remains popular even in the digital age.
Popular developers: D-76/ID-11 (fine grain, classic tonality), HC-110 (versatile, long shelf life), XTOL (fine grain, good shadow detail), Rodinal (sharp grain, high acutance, available since 1891), DD-X (modern, pushable). Each developer changes the look of the final image.
ECN-2
What it is: The standard process for developing motion picture color negative film. If you’ve watched any Hollywood movie shot on film in the last 40 years, the negative was processed in ECN-2 chemistry. It’s similar to C-41 but with one critical difference: motion picture film has a removable carbon black anti-halation layer (called "rem-jet") on the back that must be stripped before development.
How it works: The film first goes through a rem-jet removal step (an alkaline pre-bath that softens the carbon layer, followed by a spray wash that physically removes it). After that, the process closely parallels C-41: color developer at 41.1°C (106°F) for 3 minutes, followed by stop, bleach, fix, and wash. The higher temperature and different developer formula produce slightly different color characteristics than C-41.
History: ECN-2 was introduced by Kodak in 1974 for use with their Eastman Color Negative II 5247 film stock. It replaced the earlier ECN-1 process. For decades, ECN-2 processing was exclusive to professional motion picture labs. Then in 2012, CineStill Film began selling Kodak Vision3 motion picture stock with the rem-jet layer pre-removed, allowing it to be processed in standard C-41 chemistry. This made the distinctive "cinema look" accessible to still photographers for the first time. Some specialty labs now offer true ECN-2 processing for still photographers who want the authentic motion picture color science.
The rem-jet layer is why you can't simply run motion picture film through a standard C-41 minilab — the carbon particles would contaminate the chemistry and scratch other customers' film.
Historical & Discontinued Processes
K-14
What it was: The legendary process used exclusively for Kodachrome film. Unlike every other color process, Kodachrome film contained no color dye couplers in the emulsion itself — the dyes were added during processing. This meant the film was essentially three layers of black & white emulsion, resulting in extremely fine grain, unmatched color accuracy, and extraordinary archival stability. Kodachrome slides from the 1930s still look vivid today.
How it worked: K-14 was staggeringly complex. The film went through over a dozen chemical baths plus precise re-exposure steps. Each of the three color layers (red, green, blue) was developed separately: the film was re-exposed to a specific color of light, then immersed in a developer containing the appropriate dye coupler. This had to be done three times, once for each layer. The entire process required expensive, specialized machinery that only a few labs in the world possessed.
History: Kodachrome was invented by two musicians, Leopold Mannes and Leopold Godowsky Jr., working with Kodak. The original Kodachrome (K-12 process) launched in 1935 as 16mm motion picture film, with 35mm still film following in 1936. It became the color film of the 20th century — Steve McCurry’s "Afghan Girl," the Zapruder film, and countless National Geographic covers were all shot on Kodachrome. K-14 (introduced in 1974) was the final evolution of the process. Kodak discontinued Kodachrome film in 2009, and the last lab capable of processing it, Dwayne’s Photo in Parsons, Kansas, developed its final roll on December 30, 2010.
C-22
What it was: The original Kodak color negative process, used from the early 1950s through the early 1970s. If your parents or grandparents shot color snapshots in the 1960s, those negatives were C-22.
How it worked: Similar in principle to C-41 but with different chemistry, longer processing times, and higher temperatures. C-22 used a prehardener step and required about 23 minutes for the complete process, compared to C-41’s roughly 12–14 minutes.
History: C-22 was introduced alongside Kodacolor film in 1955. It served the consumer market well through the 1960s, but its complexity and long processing times made it expensive for the high-volume processing that the growing snapshot market demanded. Kodak replaced it with C-41 in 1972, which was faster, more standardized, and eventually enabled the automated minilab revolution. No commercial lab offers C-22 today, though some vintage film enthusiasts attempt to develop old C-22 film stocks using modified C-41 chemistry (with mixed results).
E-4
What it was: Kodak’s original Ektachrome slide film process, used from the 1960s through the mid-1970s. It produced beautiful transparencies but used more toxic chemicals than its successor.
How it worked: Broadly similar to E-6 but with a different first developer formula and a physical re-exposure step (the film was literally exposed to bright light mid-process) rather than a chemical fogging agent. It ran at 29.5°C (85°F) — cooler than E-6 — and required about 28 minutes total.
History: Introduced in 1966, E-4 made Ektachrome processing significantly easier than the earlier E-3 process. However, its chemicals (particularly the first developer) had a short shelf life and contained ingredients that were increasingly recognized as environmental and health concerns. Kodak replaced it with E-6 in 1976. E-4 is no longer available commercially, and the original chemistry formulas are difficult to reproduce.
E-1 / E-2 / E-3
What they were: The earliest generations of Kodak’s Ektachrome reversal process. E-1 (1946) was the first process that could be done by the photographer rather than requiring return to Kodak — a revolutionary development that broke Kodachrome’s monopoly on color transparency film. E-2 (1955) and E-3 (1960s) were iterative improvements with better chemistry and shorter processing times.
History: These early processes established the principle that slide film could be "user-processable" — something Kodachrome never achieved. This philosophy carried through to E-6 and is a key reason Ektachrome-type films survived while Kodachrome didn’t: when E-6 chemistry became available to any lab, Ektachrome films could be processed anywhere, while Kodachrome remained locked to an ever-shrinking number of specialized facilities.
ECN-1
What it was: The predecessor to ECN-2, used for motion picture negative film from the early 1960s through the mid-1970s. Eastman Color (using ECN-1 processing) gradually replaced Technicolor’s three-strip dye-transfer process as the primary color system for Hollywood films.
History: ECN-1 films had famously poor archival stability — many films shot on early Eastman Color stock have suffered severe color fading, which is why film preservation organizations have spent decades restoring and rescanning these negatives. ECN-2 addressed many of these stability issues when it replaced ECN-1 in 1974.
Alternative & DIY Processes
Cross-Processing
What it is: Deliberately developing film in the "wrong" chemistry for creative effect. Most commonly, this means running E-6 slide film through C-41 color negative chemistry, which produces negatives with wildly saturated colors, heavy contrast, and unpredictable color shifts. The reverse (C-41 film in E-6 chemistry) is less common and produces low-contrast transparencies with muted colors.
History: Cross-processing became popular in fashion and music photography during the 1980s and 1990s. Photographers like David LaChapelle and Terry Richardson used it extensively for its punchy, surreal aesthetic. It was a staple of Lomography culture in the 2000s. While it’s less trendy today, many photographers still cross-process for its distinctive look, and most labs will do it on request.
Results vary dramatically between film stocks. Fujichrome Provia and Velvia cross-process with intense greens and blues; Kodak Ektachrome tends toward warm yellows and magentas.
Caffenol
What it is: A homemade black & white film developer made from instant coffee, vitamin C (ascorbic acid), and washing soda (sodium carbonate). It sounds like a chemistry experiment gone wrong, but it genuinely works — the caffeic acid in coffee is a functioning photographic developing agent. The results have a characteristic soft, slightly grainy look with warm brownish-black tones.
History: Caffenol was first described by Dr. Scott Williams of the Rochester Institute of Technology in 1995 as a teaching tool to demonstrate developing agent chemistry. It was popularized online in the mid-2000s by the film photography community and became something of a gateway to home developing — the idea that you could develop film with grocery store ingredients lowered the psychological barrier to trying darkroom work. Multiple refined recipes exist: Caffenol-C (basic), Caffenol-C-M (with added contrast), and Caffenol-C-L (low-contrast, for high-ISO films).
Stand Development
What it is: A technique rather than a separate chemical process. The film is placed in a highly diluted developer (typically Rodinal at 1:100 or higher dilution) and left to sit for 30–60 minutes with little or no agitation. The developer exhausts itself in the highlights (where more silver needs to be developed) while continuing to work in the shadows, producing negatives with compressed highlight detail, open shadows, and a unique tonal quality.
Why people use it: Stand development is remarkably forgiving. Because the developer self-regulates through exhaustion, the exact development time matters much less than in conventional processing. Many photographers use it as a "universal" approach — you can develop almost any B&W film at almost any speed on the same reel with the same time, and get printable negatives. It’s especially popular for pushing high-speed films, where it pulls detail out of deep shadows without blocking up highlights.
Monobath
What it is: A single-solution process that combines developer and fixer in one bath. You pour it in, wait a few minutes, pour it out, and you’re done — no multi-step process, no timing critical handoffs between chemicals. The developer acts first (because development is faster than fixing), and by the time the fixer begins dissolving unexposed silver, the developed image is already established.
History: The concept dates back to the 1880s, but practical monobaths weren’t commercially viable until the mid-20th century. New55’s R5 Monobath (2016) and CineStill’s Df96 (2018) brought the concept to a modern audience. Monobaths are now popular with beginners and anyone who wants the simplest possible home developing workflow. The trade-off is less control over contrast and grain compared to traditional two-bath processing.
Quick Reference
| Process | Type | Result | Status |
| C-41 | Color negative | Orange-masked negatives | Active |
| E-6 | Color reversal | Positive transparencies | Active |
| Standard B&W | B&W negative | Silver negatives | Active |
| ECN-2 | Motion picture | Color negatives (rem-jet) | Active |
| K-14 | Kodachrome | Positive transparencies | Discontinued 2010 |
| C-22 | Color negative | Color negatives | Replaced by C-41 |
| E-4 | Color reversal | Positive transparencies | Replaced by E-6 |
Sources
- → Kodak: ECN-2 Processing — official Kodak motion picture processing specifications
- → Ilford HP5 Plus Technical Data Sheet — example B&W processing specifications and developer recommendations
- → Kodak Portra 400 Technical Data — C-41 processing specifications
- → Fujifilm: Film Processing — Fujifilm’s CR-56 and C-41 compatible processing notes
- → Wikipedia: Kodachrome — comprehensive history of K-14 processing and the film’s cultural impact
- → Wikipedia: C-41 Process — technical overview and history of color negative processing
- → Wikipedia: E-6 Process — technical overview and history of color reversal processing
- → Caffenol.org — recipes and community resources for coffee-based film development
- → CineStill Film — background on rem-jet removal and ECN-2/C-41 compatibility
Processing temperatures, times, and historical dates are drawn from manufacturer technical publications and established photographic references. If you spot an error, please let us know.
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TLR Companion is a free light meter app with built-in profiles for 22 film stocks across all of these processes — including reciprocity correction for long exposures and push/pull EI calculation. Learn more