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The E-4 process is a now outdated process for developing color reversal (transparency) photographic film, which was introduced in 1966.
The process is infamous for two reasons:
First, it uses the highly toxic boron hydride-based reversal agent tertiary butyl-amine borane (TBAB). [lower-alpha 1] [1] : 379, Table LXVI Early releases of the consumer-sized version of the chemistry provided the TBAB in the form of a tablet, possibly to avoid the possibility of inhalation. [2] This was later changed to loose powder, likely as a countermeasure against inadvertent ingestion of the substance.
Second, the prehardener agent contains formaldehyde and 2,5-dimethoxytetrahydrofuran, [1] : 377, Formula 269 which when mixed generates succinaldehyde, a noxious gas which has been likened to tear gas. [2] Process E-6 films are hardened during manufacture, eliminating the prehardener step altogether and allowing them to be processed at 100 °F (38 °C).
Ektachrome film has three separate light-sensitive layers; each layer is sensitive to a different group of wavelengths corresponding to red, green, and blue colors. When the film is exposed, each layer records a latent image based on its sensitivity. A yellow filter prevents blue light from exposing the green- and red-sensitive layers, which have some sensitivity to blue light. [3]
The E-4 process is faster than E-3; whereas E-3 required 15 steps and up to 70 minutes from start to finish, [2] [4] : 30–31 E-4 was completed in approximately 50 minutes over 13 steps. [5] E-4 runs at 85 °F (29 °C), [5] about 10 °F (6 °C) higher than E-3. The temperature tolerance is ±1 °F for prehardener, ±1⁄2°F for the first developer, and ±2–5 °F for all other steps. [5] The ME-4 process was a motion picture variation of the E-4 process.
The major change for E-4 was the inclusion of a chemical reversal agent, which permits processing of the film without the manual re-exposure/fogging step required by the predecessor E-1 / E-2 / E-3 processes. [2] [5]
Total darkness is required during the first four development steps; normal room light can be used for the remaining steps. [5]
| Step | Schematic | Time (min.) | Temp. | Description | ||
|---|---|---|---|---|---|---|
| 1 | Prehardener | 3 | 85 °F (29 °C) ±1 °F | Tempers film for high-temperature processing | ||
| 2 | Neutralizer | 1 | 83–87 °F (28–31 °C) | |||
| 3 | First developer |  | 7 | 85 °F (29 °C) ±1⁄2°F | Conventional black-and-white developer used to transform silver halide crystals exposed in all three layers as a negative image. | |
| 4 | First stop bath | 2 | 83–87 °F (28–31 °C) | Solution should not be reused for second stop bath (step 7) | ||
| 5 | Wash | 4 | 80–90 °F (27–32 °C) | Running water | ||
| 6 | Color developer |  | 9 | 83–87 °F (28–31 °C) | ||
| 7 | Second stop bath | 3 | 83–87 °F (28–31 °C) | Solution should not be reused from first stop bath (step 4) | ||
| 8 | Wash | 3 | 80–90 °F (27–32 °C) | Running water | ||
| 9 | Bleach |  | 5 | 83–87 °F (28–31 °C) | Convert metallic silver to soluble particles | |
| 10 | Fixer |  | 6 | 83–87 °F (28–31 °C) | Dissolve silver particles, which can be recovered after processing | |
| 11 | Wash | 6 | 80–90 °F (27–32 °C) | Running water | ||
| 12 | Stabilizer | 1 | 83–87 °F (28–31 °C) | |||
| 13 | Dry | var. | <110 °F (43 °C) | |||
E-4 processed film is color stable for about 30 years. [6]
The process largely was phased out in 1976 with the introduction of the E-6 process, which is more environmentally friendly due to its lack of toxic chemicals. E-6 avoids the use of TBAB by adding a separate reversal bath containing the tin salt stannous chloride.
The E-4 process has been discontinued since 1996; after 1976 it was used solely for Kodak IE color infrared film, [7] due to a legal commitment by Kodak to provide process support for 30 years after introduction. Kodak discontinued E-4 processing in 1985, but independent photofinishers continued to support the process. [8] The E-4 chemicals were reverse-engineered and substitute formulae were published in the British Journal of Photography Annual in 1977. [1] : 374
Film stock is an analog medium that is used for recording motion pictures or animation. It is recorded on by a movie camera, developed, edited, and projected onto a screen using a movie projector. It is a strip or sheet of transparent plastic film base coated on one side with a gelatin emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of the crystals determine the sensitivity, contrast and resolution of the film. The emulsion will gradually darken if left exposed to light, but the process is too slow and incomplete to be of any practical use. Instead, a very short exposure to the image formed by a camera lens is used to produce only a very slight chemical change, proportional to the amount of light absorbed by each crystal. This creates an invisible latent image in the emulsion, which can be chemically developed into a visible photograph. In addition to visible light, all films are sensitive to X-rays and high-energy particles. Most are at least slightly sensitive to invisible ultraviolet (UV) light. Some special-purpose films are sensitive into the infrared (IR) region of the spectrum.
Kodachrome is the brand name for a color reversal film introduced by Eastman Kodak in 1935. It was one of the first successful color materials and was used for both cinematography and still photography. For many years, Kodachrome was widely used for professional color photography, especially for images intended for publication in print media.
Photographic processing or photographic development is the chemical means by which photographic film or paper is treated after photographic exposure to produce a negative or positive image. Photographic processing transforms the latent image into a visible image, makes this permanent and renders it insensitive to light.
Photographic paper is a paper coated with a light-sensitive chemical formula, like photographic film, used for making photographic prints. When photographic paper is exposed to light, it captures a latent image that is then developed to form a visible image; with most papers the image density from exposure can be sufficient to not require further development, aside from fixing and clearing, though latent exposure is also usually present. The light-sensitive layer of the paper is called the emulsion. The most common chemistry was based on silver halide but other alternatives have also been used.
In photography, reversal film or slide film is a type of photographic film that produces a positive image on a transparent base. Instead of negatives and prints, reversal film is processed to produce transparencies or diapositives. Reversal film is produced in various sizes, from 35 mm to roll film to 8×10 inch sheet film.
The E-6 process is a chromogenic photographic process for developing Ektachrome, Fujichrome and other color reversal photographic film.
In the processing of photographic films, plates or papers, the photographic developer is one or more chemicals that convert the latent image to a visible image. Developing agents achieve this conversion by reducing the silver halides, which are pale-colored, into silver metal, which is black when in the form of fine particles. The conversion occurs within the gelatine matrix. The special feature of photography is that the developer acts more quickly on those particles of silver halide that have been exposed to light. When left in developer, all the silver halides will eventually be reduced and turn black. Generally, the longer a developer is allowed to work, the darker the image.
Color photography is photography that uses media capable of capturing and reproducing colors. By contrast, black-and-white or gray-monochrome photography records only a single channel of luminance (brightness) and uses media capable only of showing shades of gray.
The gelatin silver process is the most commonly used chemical process in black-and-white photography, and is the fundamental chemical process for modern analog color photography. As such, films and printing papers available for analog photography rarely rely on any other chemical process to record an image. A suspension of silver salts in gelatin is coated onto a support such as glass, flexible plastic or film, baryta paper, or resin-coated paper. These light-sensitive materials are stable under normal keeping conditions and are able to be exposed and processed even many years after their manufacture. The "dry plate" gelatin process was an improvement on the collodion wet-plate process dominant from the 1850s–1880s, which had to be exposed and developed immediately after coating.
C-41 is a chromogenic color print film developing process introduced by Kodak in 1972, superseding the C-22 process. C-41, also known as CN-16 by Fuji, CNK-4 by Konica, and AP-70 by AGFA, is the most popular film process in use, with most, if not all photofinishing labs devoting at least one machine to this development process.
Instant film is a type of photographic film that was introduced by Polaroid Corporation to produce a visible image within minutes or seconds of the photograph's exposure. The film contains the chemicals needed for developing and fixing the photograph, and the camera exposes and initiates the developing process after a photo has been taken.
In infrared photography, the photographic film or image sensor used is sensitive to infrared light. The part of the spectrum used is referred to as near-infrared to distinguish it from far-infrared, which is the domain of thermal imaging. Wavelengths used for photography range from about 700 nm to about 900 nm. Film is usually sensitive to visible light too, so an infrared-passing filter is used; this lets infrared (IR) light pass through to the camera, but blocks all or most of the visible light spectrum; these filters thus look black (opaque) or deep red.
Ektachrome is a brand name owned by Kodak for a range of transparency, still and motion picture films previously available in many formats, including 35 mm and sheet sizes to 11 × 14 inch size. Ektachrome has a distinctive look that became familiar to many readers of National Geographic, which used it extensively for color photographs for decades in settings where Kodachrome was too slow. In terms of reciprocity characteristics, Ektachrome is stable at shutter speeds between ten seconds and 1/10,000 of a second.
Fogging in photography is the deterioration in the quality of the image or the negative caused either by extraneous light, other electromagnetic radiation, radioactivity or the effects of a processing chemical. It is seen either as deposition of silver or dyes across all or part of the image unrelated to the original exposure. It can be confused with chemical staining that can be produced from poorly compounded developer, contamination of processing baths or poor washing after processing.
A chromogenic print, also known as a C-print or C-type print, a silver halide print, or a dye coupler print, is a photographic print made from a color negative, transparency or digital image, and developed using a chromogenic process. They are composed of three layers of gelatin, each containing an emulsion of silver halide, which is used as a light-sensitive material, and a different dye coupler of subtractive color which together, when developed, form a full-color image.
The E-2 process and E-3 process are outdated processes for developing Ektachrome reversal photographic film. The two processes are very similar, and differ depending on the film. Kodak sold kits that could process either kind of film.
K-14 was the most recent version of the developing process for Kodak's Kodachrome transparency film before its discontinuation. It superseded previous versions of the Kodachrome process used with older films.
Photographic film is a strip or sheet of transparent film base coated on one side with a gelatin emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of the crystals determine the sensitivity, contrast, and resolution of the film. Film is typically segmented in frames, that give rise to separate photographs.
Photographic hypersensitization refers to a set of processes that can be applied to photographic film or plates before exposing. One or more of these processes is often needed to make photographic materials work better in long exposures.
The third in the series of color developing agents used in developing color films, commonly known as CD-3, is chemically known as N-[2-[(4-Amino-3-methylphenyl)ethylamino]ethyl]methanesulfonamide Sesquisulfate Monohydrate. In color development, after reducing a silver atom in a silver halide crystal, the oxidized developing agent combines with a color coupler to form a color dye molecule. CD-3 is used in many processes including VNF-1 and the E-6 process.
Color IR film has one drawback. It is not readily processed because it requires the old E-4 chemistry.
Eastman Kodak no longer offers processing for E-4 films such as Ektachrome Infrared and Kodak Microphotography color-slide films. However, there are more than a dozen independent labs in the U.S. that offer this service.
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