Key technologies for prepressing backlit photos
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Photo prepress processing is a guarantee of print quality. In the prepress processing, since the photo original is affected by factors such as shooting technique, equipment, environment, etc., the original has different degrees of defects. In addition, different photos have different artistic styles and required effects, which requires pre-press production not only to correct the lack of photos, but also to try to deal with the artistic effects pursued by the author.
Light is the lifeblood and soul of photography. According to the characteristics of light used in photography, photos can be divided into works of Shunguang and backlights (including side backlights). Shooting in the light, the light source is in front of the subject (including the front side). Shooting in backlight (or side backlight) with the light source behind the subject (or on the left and right sides of the shot). Backlight photography can enhance the texture of the subject and the rendering of the atmosphere, enhance the impact of the visual and the depth of the picture, so that the photographs are rich in color, with strong contrast and strong sense of space. In backlight photography, the light method is one of the most effective methods of photographic creation. Backlighting photos can turn ordinary objects into fascinating images and beautify mediocrity. Therefore, it is a common method used in many photographic art. However, due to the high contrast and many changes in backlight photography, most of the main parts are in the shadows. It is not easy to shoot the ideal effect. The photographic works often have a dark front light, the quality of the light is not ideal, and the contrast is too large. The brightness and dark tone levels are not ideal, and there is a disadvantage that the color texture of the front of the object is difficult to fully express. Some of the backlight works are caused by the influence of the stray light, and unnecessary light spots or fog light and shadow are generated directly in the picture. Affects the performance of levels and tones. All of these require the production staff to master the characteristics of the backlight photo, improve their artistic accomplishment and aesthetics, make full use of advanced prepress equipment and technology in the prepress production process, and accurately grasp the information institute of Fujian Academy of Agricultural Sciences. Lin Qi watermarks the key technology of the backlight photo processing to deal with the style of the backlight works, according to the photos and printing characteristics to select the best process to improve the quality of production. To sum up, we should pay attention to the following aspects.
First, grasp the tone of the backlight photography
Because the backlight works with light, the color tone changes greatly, and various color tone can be formed. Among the large number of backlights, some are mainly warm colors, and some are mainly cool colors. In addition, some of the colors of the picture look like some color casts. In fact, the author deliberately pursued it, so it cannot be considered as a color cast. Therefore, mastering the exact tone of the picture in copying is the prerequisite for doing a good job of color reproduction.
For example, a retro-reflective work with a person as the main body should properly control the tone of the person's skin color when copying. The color of the person's skin should have a proper sense of brightness, but it must be consistent with the overall tone of the picture to achieve harmony and unity. In this way, the color reproduction can truly reflect the characteristics of the backlight works.
Second, pay attention to the light processing of backlight photography
Backlight photography is characterized by the full and accurate use of light, the originals are very particular about the use of light, therefore, pre-press production must deal with the beauty of light, first of all to distinguish whether the direction of the main light is side backlight, or backlight. Distinguish the light-receiving, mid-tone, and dark-tone surfaces. The brightness of the midtone surface shall not exceed or be equal to the light receiving surface; the brightness of the dark adjustment surface shall not exceed or be equal to the midtone surface. Taking a photo of a person as an example, if the dark relationship of the face is inverted or flat, even if the skin color is handled well, it still gives a feeling of discomfort, so the color of the person cannot be simply emphasized and the relationship between the face and the face is lost. The following points should be mastered in copying: (1) Pay attention to the light effect of the overall picture, and have a strong sense of light. The version is to be embarrassed, and the contrast should be opened. The color of the light-receiving surface cannot be flat, and the dark tone should be deep; (2) the highlight should be bright, and the highlight should be concentrated. The highlight of the picture is the strongest, the area of the highlight is small, the smaller the area, the more concentrated the light, the higher the light can be. The ultra-high light net of the net is rich in light and medium-level, in order to highlight the brightness of the highlight; (3) to highlight the main light. Some originals are cluttered with light, and it is impossible to distinguish between front light and back light. need
To make a partial correction on the original, consciously concentrate the main light to the central focus of the picture, and compress the four astigmatism to concentrate the line of sight, highlight the theme, and enhance the artistic effect; (4) handle the reflection. Note that the intersection of the person's face on the dark side and the reflection is obvious, and some reflections require artistic processing.
Third, emphasize the light of the picture
Photography is the use of light to depict the shape, color, tone level, perspective and texture of the subject. Therefore, in the reproduction must pay attention to the light characteristics of the backlight works. For the analysis of different light angles (including the use of color light), a specific analysis should be made. In the copying, it is necessary to grasp the light change of the picture, so that the bright part of the picture should be brightened, the dark place is darkened, and a certain contrast is maintained, and the scene is far and near, the level is rich, and there is a good perspective and three-dimensionality. Effect. For example, a close-up of a character, a large area of rich color to set off a small area of bright color. And this small area of bright color, in the picture plays a finishing touch. If you give up or ignore the effect of this small area of bright color in copying, it will make the picture gray and light, and lose the charm and style of the character's backlit works.
Fourth, grasp the performance of the texture
Backlit works also have a better expressive effect on the surface texture of the object. Therefore, the reproduction of the texture is also emphasized in the reproduction. For example, for a snow scene, you should consciously enhance the contrast of the contrast in the copy, and improve the brightness.
Adjust the level and the second light level, and maintain a certain amount of color, in order to facilitate the texture of the snow. For other types of backlight works, we must also pay attention to the performance of the texture, otherwise, it will lose the inherent characteristics of the backlight works.
Fifth, the color should be thick and vivid
Backlighting works have the characteristics of rich color tone, large color saturation and strong contrast of density. However, due to various specific conditions, the printed matter is inferior to the original in terms of contrast contrast, color saturation and gloss. Therefore, in copying, the color quantity of each color version should be used enough, and attention should be paid to the vivid color and the intensity of the layer to reflect the thick and vivid color of the backlight. For example, a retro-lighted work with a white kitten as the main body, the main body is in dark and cold colors, the front of the cat is illuminated by warm light, the edge of the cat body has a cool-colored outline, and the front of the main body is in the middle of the cold and warm phase. The hue creates a rich and heavy picture of color. In this regard, there are two points to pay attention to when copying: First, on the basis of ensuring a large amount of background color, the relationship between the main body, the contour ray and the background color quantity is handled to prevent the subject from jumping out of the picture and affecting the harmony and unity of the whole picture. The second effect is to pay attention to the color sharpness of the main gradient contour to enhance the vividness of the whole picture and achieve a pleasing copying effect.
Sixth, pay attention to the setting and adjustment of the middle adjustment
Controlling the amount of color used in the midtones is very important for the production of backlights. It can stabilize the brightness and darkness of the ink, and avoid the phenomenon of shallow or deep tone. The reproduction of the color reversal film should be based on keeping the bright color bright, the middle adjustment level rich, and the dark adjustment thick, and the amount of compression should be emphasized. In the reproduction of color photographs, it is necessary to consciously improve the clarity based on the control of the middle, especially to emphasize the intensity of the highlights. In the reproduction, there is a side-lighting work with a large light-receiving surface, a small level of tone, and an unsaturated color. The color amount should be appropriately increased on the basis of maintaining the level to achieve a harmonious and balanced reproduction of the color tone. The setting and adjustment of the middle adjustment must first satisfy the visual habits of the human eye. A portrait photography photo, whether it is a smooth film or a backlight, the middle is too light, the skin color is too thin and thin, the middle tone is too deep, the skin color is dark and dark, even if the brightness is more than 5%, the dot value is also It will give people a feeling of discomfort.
The key to the three-point calibration of the backlight (side backlight) is to control the midpoint. In addition to using the midpoint control of the gray ladder, it is more important to select a block of the face as a control point. The trick is to select which part of the face as the control point and how to scientifically convert the density into the dot value. According to the operating experience, the forehead part should be used as the intermediate control point. Based on the red dot value, the density value of the forehead part of the reversal film is 1.2, and the area of the dot is not more than 50%, and the control is 45% to 48%. When the density of the back-lighting face is large, the sub-high light is used as the white field calibration point, and the gradation curve is reduced by 10%, and the maximum black field calibration density value is used to fully express the middle and dark tone levels of the face. The level curve is steeped, and the black version is used to open the level of the hair and the dark part of the face. If the brightness of the face is light, the white field calibration density value should be small to deepen the color level of the bright tone; and the black field calibration density value should be small.
According to the size of the face density of the portrait photography original, it is divided into three categories: 1 exposure is normal. The contrast photo of the density contrast standard, the side backlight, the face body is in the bright, middle, and it is proportional to the brightness, is in the best visual brightness range. Generally, by setting the highlight and dark tone to set the density value and the corresponding gradation curve and color correction, the gradation and color change of the original skin color can be better reproduced without any modification and adjustment. 2 overexposed. High-profile photos with small contrast in density, the main part of the face is bright and thin, and the brightness is high, and some deepening adjustment is needed. To reduce the brightness, move closer to the standard brightness to achieve better tone contrast and visual brightness. 3 underexposed. The back-light photo with large contrast of density has a dark and deep main part, and the brightness is low. It needs to be lightened to improve the adjustment. On the one hand, based on the automatically set highlight and dark density values, artificially add some set density values, which need to lose some highlight levels and compress some dark levels; on the other hand, adjust the middle to the dark areas. The curve is pulled down, minus 5% or the required dot value to improve the brightness and close to the standard brightness to achieve better tone contrast and visual brightness.
Seven, control tone contrast
The wide range of density and rich color tones are another feature of the backlighting work. In the case where the print density range is limited (about 1.8) and the color change is far less than the backlighting work, the plate making and printing process conditions should be fully utilized. The dark color of the black version is enough, and the level and color of the bright tone should be controlled, so that the color gamut of the reproduction is wide and vivid. Copy the side backlight photo, on the basis of controlling the stability of the intermediate adjustment, it is necessary to make the tone longer, in order to facilitate the three-dimensional and perspective effects of the scene in the picture. Especially for landscape works, it is necessary to make the tone longer, which is more conducive to the performance of the side-back landscape works. In addition, on the basis of maintaining a good mid-tone in the copy, it is necessary to appropriately improve the brightness of the bright tone, and if necessary, some partial bright spots can be made into a net to enhance the crystal clearness of the picture. On the basis of maintaining the level, the dark tone is thicker in color, which is conducive to strengthening the spatial and three-dimensional sense of the whole picture, maintaining a good brightness ratio and color contrast, and achieving a pleasing copy effect. In practical work, for a work with a flat tone, the color should be increased on the basis of maintaining the clarity; for a work with a dark tone, the color of a certain color should be appropriately lowered while keeping the tone moderate. Quantity, in order to achieve good copying results.
Eight, the calibration points of each color version
Some side-backed, backlit portraits have a large dark-adjusted area, a high color density, a yellowish tint or a brownish tint. At the time of calibration, the yellow and red versions of the dots are more than 80%, or even 90%, which is close to the dot area of the deep primary color (100%). Since the dot value of this area changes greatly during printing, even if the ink is printed according to the standard, the dark tone of the printed skin color will be reddish, the "fire" is displayed, and then the deep primary color is not saturated, and the printing time is It is difficult to balance the two. If the printing takes into account the skin color, the amount of ink is small, the skin color can be, but the deep primary color is not saturated; if the printing takes into account the deep primary color, the amount of ink is sufficient, and the skin tone is reddened. Therefore, this operation point is taken against this situation. Corresponding measures. Such a color separation film can achieve a good copying effect and printability. If encountered Some originals have defects that cannot be graded. The color separation should be based on the dark tone and the red version is controlled at around 75%. When the amount of deep primary color is not enough, then select this area for local deepening to open the distance between the two. Such a color separation plate can not only make the dark tone color moderate, but also take into account the saturation of the deep primary colors to achieve the best of both worlds.
In short, in the pre-press production of backlight photos, we have to carefully analyze the original to see if the color cast, level, clarity, color saturation, etc. are good, fully understand the author's creative intentions and the artistic effect that he wants to achieve. And according to the pre-press advanced equipment to carry out the necessary processing and promotion of the original, so that the true artistic effect and printing quality of the work is fully reflected.