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Chapter V color imaging method deletion

It is within the category of multilayer color films, whether they are reversal, negative, or positive films. All of them operate according to the Subtractive theory of deletion. These films are sometimes called Integral Tripack Color films or Integral Tripack Color films

Multilayer color films:

The vast majority of color films currently on the market are in use

With a third name, Monopack Films.

These films consist mainly of the layers shown in Figure 46, and they contain three sensitive layers, each of which was prepared to record one of the three primary colors (red - green - blue). One has one pillar carrying the three sensitive layers. The following is an explanation of the functions of each:

(1) The upper layer is sensitive to blue rays only, so it only records blue colors. If these blue colors are mixed with another color, then it records only the blue percentage of the mixed color. For example, if the object was magenta (i.e. blue + red), it will record only the blue part of it, and if it was cyan, it will only record the blue part of it.

b) The upper blue-sensitive layer is followed by another insensitive layer, but it has a yellow dye that acts as a yellow filter in order to absorb any remaining blue-rays that are likely to pass through the upper sensitive layer to the lower two layers, while this yellow filter allows red and green rays to pass. from which its yellow color is formed (Fig. 47).

It is clear that the wisdom behind the existence of this yellow filter is that it blocks blue rays, which, if it penetrates into any of the two following sensitive layers, will effectively affect them, because in addition to the sensitivity of the second layer to green rays, and the sensitivity of the third layer to red rays, they are also sensitive to blue rays. ) Figure 46, and therefore it must be prevented from reaching them, otherwise it will record two colors each instead of one.

light wavelength (angstroms)

Blue-sensitive layer, yellow filter, green-sensitive layer, colorless gelatin layer, infrared-sensitive layer, anti-halo coating, film support

(fig. 46)

ago (spectral sensitivity in the three layers of the colored film:

The closely spaced shaded areas indicate the light rays that are recorded in each of the three sensitive layers

As for the shaded areas separated by lines, they indicate the blue rays that are also affected by each of the two lower sensitive layers, which could also have been recorded had it not been for the presence of the yellow filter located after the blue-sensitive layer (as this filter works to absorb the blue rays, so it does not reach the two lower layers). rays

(c) After both green and red rays have been exhausted only through the yellow filter, they are met by the second layer that is sensitive to green rays only, and it is of the orthochromatic family that is completely insensitive to red rays, and thus will not be affected by the passage of those last rays; And to record only those green colors only. As for the red rays, they will pass through them without causing any photochemical reaction. Likewise, it records on this second sensitive layer also any part of the green rays that are mixed with others, as it records, for example, the green part that is reflected by cyan objects.

(D) As for the third layer, it is highly sensitive to red rays, and even assuming that a portion of the green rays enters this third layer, it will not register the effect of green, as it is absolutely insensitive to those green rays. Or it may be sensitive to these rays to a very small extent so that it does not require placing an additional filter in front of it to absorb these rays, and we do not mean by saying that this third layer is sensitive to red rays that it only records the pure red color, but we also mean its ability to record the red part of the colors In which the red color is mixed with another, it records, for example, the red part of the yellow or scarlet rays reflected from objects.

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light wavelength (angstroms)

(Fig. 47) Spectral characteristics of the yellow filter that is placed after the blue-sensitive layer in the color films: It is seen in the diagram that this filter absorbs blue rays and allows red and green to pass through it.

And in the manufacture of the three sensitive layers, it is taken into account that the speed of sensitivity of the lower layer is higher than that of the upper one, in order to compensate for the decrease in the amount of radiation that results from its passage through the upper sensitive layer and the yellow filter (referred to).

In item B, p. 144). Thus, we see that the multi-layered color film will carry within it, after exposing it, three images that are exactly similar to those that we have called separation negatives.

Color Separation Negatives (p. 114) Similar to what we are used to with regard to black and white film, there is also an anti-halation layer that is sometimes placed under the support of the film (Figures 57, 08, on page 200) or between the support of the film and the lower radiation-sensitive layer. (Fig. 46 p. 144) In some color films, there may not be a separate layer carrying the yellow filter next to the upper blue-sensitive layer, but rather the filter is located within this upper blue-sensitive layer (Fig. 58 p. 205), and it performs the same previous work. Referring to it in the article, p. 144, as an example, Orwocolor Positive Film Pe5

orwocolor Positive Film PC7,