The Techniques and Key Points of Reproduction (V)

6. The white-field setting pays attention to the relationship between the three aspects.

(1) Pay attention to the relationship between the high-gloss neutral white and the special light source colors and pan-colors that photographers and artists pursue. Because the highlight color change is very rich and delicate, if you use the special light source color and pan-color as the sampling point, set it with the AUTO key, and correct it to neutral white, then you lose the high light and rich subtle color changes.

(2) Pay attention to the relationship between high light modulation and bright tone and middle tone.

The highlight setting is based on the curve. The depth and depth of the setting will affect the change of the middle tone. The rule is that the highlight setting is to be deepened and the depth is reduced by 5%, then the middle tone is deepened and reduced by 2.5%. The effect is approximately 1/2.

Therefore, when highlighting points are selected and settings are made, attention should be paid to changes in the midtones.

(3) Pay attention to the relationship between high light and basic light color.

The deepening or lightening of the highlight setting will affect the basic color of the highlights, mainly affecting the brightening of the basic colors toward the white field. Such as the M version of the light pink, C version of the light blue, light green, Y version of the light yellow, etc., the dot value is about 5%, it often conflicts with the white field settings. If the white field is set too high, ie the density value is too large and the dot value is too small, the light tone is affected. If you take care of light tones, the white field is slightly flat, ie, if the density value is too large and the dot value is too small, the light tone is bright enough. Therefore, the main aspects should be considered when setting. If the whole picture is dominated by the contrast, and the white field is required, then some basic colors will be affected. If the picture is dominated by light tones (such as watercolors, gouache, etc.), the white field needs to be slightly flat, which affects the brightness of some highlights.

7. The standard and judgment method of correct setting of highlights.

Set the original density contrast criteria. The correct highlight setting is:

(1) The distance between the high-gloss white and the extremely high light of the required level is taken as the standard, paying particular attention to the boundary between 0% and 3%. This is a jumping part of the printing network (the gravure is the boundary between 0% and 5%). Extremely high light is 0%, and the level of highlight white is C5%, M3%, and Y3% (gravure is C7, M5, Y5). According to this standard is:

a. If the highlight part of the required level is set to 0% or the set dot value is too small, which is 1-2%, the printing cannot be printed, resulting in a high level of light that does not require a dot, indicating a high optical density value Set too large, the dot value is too small. This value does not result in loss of high-light levels, but also affect the lack of highlighting the basic color.

b. If the extreme highlights that should be screened are set to the dot value that can be printed out by the printing, the high optical density value is set too small and the dot value is too large. This caused the printed products to be dark and dull.

c. The density of the original document is dense and needs high light to brighten the light, and the second highest light can be set as a net.

d. The original color density is light and requires high light and darkening, so the extremely high light can also set the outlets.

(2) The correct highlight sets three criteria for the density value. 1 extremely high light achieves 0% netting, requiring a high level of white offset printing dot values ​​of C5%, M3%, and Y3%. 2 The basic colors of highlights and highlights do not affect or have little effect. 3 Set the opposite color of the most vivid and bright primary or interstellar color to 0% or the minimum dot value required. For example, the highlight of a person's skin color is based on the reversed version of the C version. The general periodical magazine can be set to 0%. Advanced products such as albums and calendars can be set to 3% to 5%. If the C version of the net is too large, it means that the white field set the density value is too small. Conversely, for advanced products, skin highlights require a dot value of 3% to 5%, and a setting of 0 to 1% indicates that the white field setting density is too large.

8. Gravure electro engraving process scanning color separation high light calibration law.

According to the dot change rule of engraved cylinder and OPP proofing, the highlight part of the ink is thin, and the small dot is easy to be reduced. Therefore, when scanning the color separation highlight setting, the basic white setting of the high-gloss white of the required level should be slightly larger and the minimum dot value. It is 6-7%, which is conducive to the reproduction of the small net when the engraved roller dot is transferred to the OPP film, so as to ensure the enrichment of the highlight color layer.