Development of a negative film color

The development of a negative film color is the first stage of the production of photographs color. It will be followed pulling on a paper color.

Negative a color has a strong dominant orange which makes the image difficult to interpret.

Principle

After some additive processes complex (projection of three negative monochromic or Three-color process like the process used by Prokudin-Gorskii; the Autochrome (1905) producing projectable images which could be reproduced only coarsely on paper with the techniques of the Imprimerie), negative the color modern, subtractive, appears with Agfacolor in 1936 but especially Kodacolor (fine 1941). They will be popularized only in the years 1950 with the marketing of films in cartridge 135 and will allow the pulling of tests on paper at an accessible cost. The basic principle is the superposition of three layers of emulsions sensitive respectively to the three primary colors: layer sensitive to the Bleu , separated by a layer filters yellow layers sensitive to the Vert and the Rouge . The yellow filter blocks the blue component of the light. Each of the three principal layers comprises grains of bromide of money sensitive to the light and a coupler which will make it possible to form a dye during the development chromogene. At the time of this one, each coupler reacts near the exposed money grains and releases a complementary dye of color.

These dyes are however insufficiently selective and “pollute” returned other layers:

the layer sensitized with blue is coloured in Jaune;
the layer sensitized with the green is coloured in Magenta with a yellow secondary;
the layer sensitized with the red is coloured in Cyan with secondaries magenta and yellow.

To compensate for these secondary colorings, a mask is added to the two last layers:

with the layer sensitive to the green, a yellow mask;
with the layer sensitive to the red, a magenta mask and yellow is, subtractive, red.

These masks form during the development an negative image which compensates for the dominant undesirable ones, at the price of an orange uniform color which is filtered with pulling.

The layers filter and anti-halation become transparent during the development.

The most recent films comprise a complementary layer sensitive to the magenta cyan becoming clear, for one made optimal of the soft nuances and in particular of the skin.

C41 process of development of negative film color

The C41 process of development is spread the most, as well for the amateurs as for the professionals. It is compatible with the near total of the alkaline emulsions color current.

In this process, only the processing time in the revealing one must be precisely respected; for the other stages, the indications constitute a standard practice allowing an automation of the treatment (machines with rollers or transfer). It is recommended to proceed to a temperature setting of negative (5 minutes with 38 °C, dry) before plunging it in the first bath.

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