Bleach bridging

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Bleach bridging is a photographic development process that enables silver and dyes to be preserved in one color film at the same time.

You can leave out the bleach bath when developing the negative , leaving the silver in the individual layers of color. In the case of copies of such negatives, this leads to more faded colors, since the silver absorbs the entire spectrum of white light. In addition, the contrast is increased. Highlights look eroded and the shadows become very dark and poor in drawing.

You therefore have to take special precautions at the location in order to achieve good results. Since the silver increases the density of the negative so much, an underexposure by about one f-stop is advisable. You can also experiment with the lighting to improve the result. The very sharp-edged appearance can be weakened somewhat with diffusion filters. The bleach bath bridging usually emphasizes the existing grain size and can therefore lead to problems, especially with highly sensitive material.

If you are dissatisfied with the result, you can develop a bleach-bridged negative again and remove the silver from the material. However, if the special requirements for bridging the bleach bath were already discussed at the location, the result is a very flat, illuminated negative with little contrast, i.e. the opposite of what you actually wanted to achieve. A partial bridging is not possible or not very recommendable because the chemical process is designed to be run through completely. Premature removal from the bleach bath can lead to very inconsistent results.

An alternative to this is bridging the bleach bath when developing the copy. You can proceed as with bridging the bleach bath and get similar effects. In contrast to the bleaching bath bridging with the negative, the copy is shown directly and does not have to be copied first. As a result, the colors are desaturated , as is the case with a copy of a negative with a bleach bath , but they also appear darker and not so pale.

A modification of this process is the so-called ENR process. ENR stands for the three technicians at Technicolor Rome who are credited with inventing this process. Similar techniques are also known under the names CCE (Color Contrast Enhancement, e.g. in the film Sieben ) and NEC (Noir En Couleur, e.g. in the film City of Lost Children ). Here, the bleach bath is run through as normal, but instead of using the fixer afterwards, the film is put into a black and white developer again . In contrast to bridging the bleach bath, the amount of silver remaining in the film can be controlled in this way. Dark and faded colors are also obtained with these techniques.

The silver remaining in the copy absorbs more light during projection and therefore heats up more. This can cause the footage to curl and cause problems with focusing.

literature

  • Dominic Case: Film technology in post-production: The compendium.