Transmission original analysis (1)

Transmitted originals have natural color positives, natural color negatives, and second originals.

A natural color film

The natural color film, also known as color reversal film, occupies a large proportion in the current draft. With the vigorous development of our country's industry, it will be adopted more in the future.

1. Natural color features

There are two kinds of natural color positive films, one is the reversal film shot, it is a double exposure of the second development by bleaching, fixing made, four around along the thick black, is a common copy of the original; the other is a color negative film The enlarged positive copy has four sides with more transparent edges and thicker particles, especially the yellow split color film. The natural color positive film is a kind of color multi-layer photosensitive material. Its film base is coated with multiple layers of emulsion (upper, middle, and lower). Each layer of photosensitive emulsion is composed of silver halide, gelatin pigment and corresponding color coupler. . The color coupling agent is a colorless and transparent organic compound, which can make the emulsion to form a complementary color of the original sense color after exposure and development. The top layer of the color coupling agent is blue light, showing yellow; the middle layer has a sense of green light, presenting Magenta; the next layer is a feeling of red light, showing blue. In order to prevent blue light from acting on the middle and lower emulsions, a yellow filter layer is applied between the upper and lower layers. Therefore, it undergoes secondary exposure and secondary development to become a color photograph with the same color as the original. As shown in Figure 8-2-1.

The contrast ratio of the photosensitivity of the natural color positive film is large and the latitude is smaller than that of the general photosensitive sheet, so the contrast is particularly strong. At the same time, because it is a transmissive original, the high-profile part of the light is very strong, due to dark areas. The layer of emulsion pigment is thick and the amount of light is very small. So the highest contrast up to 3.0 or more, normal about 2.0. The perspective and texture of the objects it photographed are extremely strong, the colors are bright and dazzling, and the light and shade levels are rich. The particles express the true effect with exquisiteness and fidelity. However, due to factors such as exposure time, color temperature deviation, improper flushing, and other factors, the three primary emulsions are unbalanced, and often appear purple, green, tea, and pale, overly boring.

The image recorded when the natural color reversal film is shot is a negative image. As shown in the figure (8-2-2), line AB is the original scene, A is a high-profile part, and B is a dark tone part. After the first black and white image was taken, the silver negative image was taken as the ab density curve. The shoulder a and the toe b exist. The shorter the two parts, the straighter the straight part and the higher the quality of the reversal film.

Due to the presence of shoulders and toes in the black and white negative images developed for the first time, the remaining undeveloped silver halide emulsions undergo double exposure and color development. After bleaching, the colored positive images A'B' are also present on the shoulders. Toe, as shown in Fig. 8-2-2, the natural color reversal film has a positive A'B' density curve different from that of the original AB. The high-level gradation is flattened, the dark tone is gradated, and the reversal film is of higher quality. Poor, the greater the difference between the brightness and darkness of the original scene, or the greater the number of shooting errors.

Therefore, when copying a plate, attention should be paid to adjustment and compensation of the tone.

2. Production requirements for natural color printing plates

Natural color original manuscript copy, currently using direct screening process and electric separation process are mostly ideal. Due to the small original size of the original color positive film, high magnification, strong contrast, and long exposure time, the line drawn on the manuscript becomes thicker and darker after separation, resulting in misregistration. Therefore, when copying, the original specification frame is made with a black film, and the original ruled line can be clearly transmitted.

The natural color original manuscript is the most original manuscript of the current electric division platemaking. The following points should be grasped according to the features of natural color positive pictures:

(1) Master the tone of each manuscript, that is, whether the scene of the manuscript is primarily cold or warm. And note that some works are the shades that the author is particularly pursuing, and cannot be treated as partial colors. If the fundamentals of the screen are not thoroughly analyzed and inaccurate, it will result in failure in reproduction.

(2) Highlighting the light The photographic light is an important means of expression for photography. The photographic light not only depicts the shape and color of the subject, but also serves to shape the character's image, enhance the atmosphere, and convey feelings. Therefore, special attention should be paid to the highlighting of the light when copying, so that the picture maintains a certain contrast. The bright one should be bright, and the dark one should be dark. Small spots of bright spots should be netted, and there should be a certain degree of contrast when talking about the light. The light should focus on the center of the picture. With a sense of light, the screen can have a sense of perspective, perspective, and three-dimensionality. Otherwise, the screen is bleak and plain, losing the characteristics of photographic art. Of course, there are also some photographic contrasts that are not large, but they are artistic. This is a different story.

(3) It is necessary to grasp the characteristics of natural color, natural change, and bright color, etc. Since the color saturation of the natural color positive film is high, and the print is affected by the performance of ink, paper, etc., the color of the printed matter is more than the color of the actual scene. Dark, there is a big gap between the two. Therefore, the electrical branching color is improved by one step over the standard color correction range, which can make up for some deficiencies. Normal color originals should be faithful to the original color. For manuscripts that are color cast or overly boring and light, they should use color tones in a rational manner and give art processing to the colors of real scenery. For example, an all-round thin original must have an overall increase in color. A group of white sheep or white geese occupies the main part of the picture, while the background sky is light in color, which can deepen the theme highlighted by the blue sky. In the process of adjustment, as long as these ideas and intentions, there are still ways to do in the process.

(4) Grasp the sharpness of the image Natural color positive film has a higher definition, and sharpness is the key to determining the copy quality. Therefore, the fine level adjustment function of the electric extension must be used. The color film should be based on the characteristics of various manuscripts. The resolution and magnification of the selected and set appropriate apertures and subtle levels of emphasis. The smooth and delicate picture is the premise of high-quality print. Special attention should be paid to the smooth face and complexion of women and children, the color of large flat blue sky, and the uniform background, etc., to prevent rough particles and the quality of outlets.

(5) For high-density high-contrast or high-density low-contrast color positive film plate, pay attention to the high, medium, low level and tone reproduction. For example, if the tone and tone of a certain tone are lost, the picture becomes boring. The color correction of color cast should not be too much, so as to avoid excessive loss of high-profile and sub-high-profile levels.

In general, natural color reproduction also requires that the colors on the screen are appropriate, the scenery atmosphere is natural, the texture of objects is strong, and the perspective is far-reaching. Because these are the basis for evaluating product quality.