The C-41 film, when exposed in the camera, receives a latent (Latin for hidden) image. Color films consist of multiple emulsion coats, each doctored so they become light-sensitive to one of the three light primary colors, which are red, green, and blue. They are imbedded in gelatin to form an emulsion. These halogens are iodine, chlorine, and bromine. These are compounds of silver combined with a halogen (Swedish for salt maker). Modern color films contain miniature light-sensitive crystals. Separating bleach and fix is not a requirement is a home darkroom setting. This is true because paper prints can be reprinted if something goes wrong, film if ruined is usually not salvageable. This works out OK but separate would be better. The color paper developing process did combine the bleach and the fix. It is not economically feasible to mass process without keeping the bleach and fix as separate chemical baths. In other words, fluids are treated, re-used and then finally discarded safely. This is accomplished by on-line electrolytic devices.īesides all the problems of keeping the solutions at specification, the lab must sewer or haul-away to an licensed waste facility. As this fluid works to remove silver salts and metallic silver, it’s silver level must be controlled. The EDTA (red) bleach is iron based and its operation depends on the level of iron oxidation. The bleach must not only be replenished, it must be aeriated. Test strips are measured and graphed with high precision.Ĭhemical tanks are filled with a tank formula and replenished, based on the graphs with a specialized replenished formula. Test films are run interlaced with customer film. Now we are talking, automatic temperature control, both heating and refrigeration. That being said, when you process at this volume, the chemistry must have an indefinite life. Additionally, the color balance of outputted prints was topnotch. Regardless of what you think, the vast majority outputted a top quality product, The standards were plus/minus 1/6 of an f-stop. Such labs as these were duplicated in countless locals worldwide. Each was sized to handle 20,000 rolls of color film a day. I was technical manager for 7 such labs in the Southeast United States.
The C-41 and E-6 processes and their cine counterparts evolved in an era where giant regional processing labs were the norm.
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