Foldable-magnetic-closure-boxes-for-garment Grey Balance And Dot Expansion Principle (5)

foldable-magnetic-closure-boxes-for-garment Grey Balance and dot Expansion Principle (5)

 

4. Setting of color separation parameters

Using gray component instead of GCR color separation can determine the black plate generation, black plate limit, total ink limit, UCA background color gain in Photoshop software, can arbitrarily adjust the parameters of "black plate generation", adjust the black plate curve shape, establish the black plate starting point and end point, the adjustment range is large, can fully meet the requirements of all kinds of original copy of black plate.

 

① Black Generation. This setup has 5 black generating function curves to choose from.

A. No black: that is, only C, M, Y three-color version curve, and no black version generated. This three-color reproduction process is generally not used, and is only used for special effects. Because the gray of the three-color overprint is unstable, the density of the dark part of the image is insufficient, and the contrast is not enough.

 

B. Light (Light) black generation: C, M, Y three-color overprinting gray, black from the medium to dark tone are removed, the amount of color ink is relatively large, the removed color part is replaced by a long tone black version, the black version starts at 35%, and the black generation curve is steep.

 

C. Medium black generation: C, M, Y three color overprint gray, black from light to dark are removed. The color amount of the three-color ink is less, and the color part that is removed is replaced by a long-tone black version, which increases the amount of the black version in the dark area, and the starting point is at 20%. This is a common curve.

 

D. Heavy black generation: From the color curve, it can be seen that the gray and black after C, M and Y overprint have a large removal amount from bright tone, medium tone to dark tone, and the amount of color ink of C, M and Y is less, while the black version is deepened accordingly, almost in the whole level of tone, the starting point is 10%, and the black generation curve is relatively close to the 45° diagonal.

 

E. Maximum black generation: the gray and black areas of C, M, and Y three-color overprinting are all removed, and there is no color ink, which is replaced by black ink. The black version has the most complete and deepest tone, playing an important role. The starting point is the state, and the black generation curve is theoretically 45° diagonal.

 

This method is generally not used, because there is currently no 10. The density of the field black ink can reach more than 2.2, which cannot reach the density value of 300% of the UCRI four-color superposition, and can not reach the density value of 340%-360% of the four-color superposition of the traditional process, which will cause the shortcomings of thin black, insufficient contrast, and poor visual effect.

 

② Total black ink limit. The set value of the black ink limit will affect the amount of C, M and Y ink in the dark area, and when the black ink limit value is increased, the amount of C, M and Y three colors of ink will be reduced. On the contrary, when the black ink limit is reduced, the amount of C, M, and Y three-color ink will increase. The default value is 100%, and most originals are set to 60% to 70%.

 

According to the law of dot increase of the current gravure electroengraving printing process and the characteristics of the original manuscript are mainly food and seeds, the black ink limit is set to 60%, that is, the black ink limit value should be lower, and the amount of three primary colors should be more.

 

③ Limit the total amount of ink. The setting of the total amount of ink limit is the sum of the four color dot values of C, M, Y and K of the normal black field setting point. At present, the total amount of ink for offset printing is generally 320% ~ 360%, and the total amount of ink for gravure engraving roller and plastic film printing is generally 300% ~ 310%.

 

5. Differences between GCR and UCR

Both gray composition replacement and base color removal reproduction techniques use black ink instead of color ink, so it is easy to misinterpret GCR as an extension of base color removal, but the two are fundamentally different.

 

(1) Different removal methods of color ink background color removal is to replace the color (background color) of the dark part of the image with black ink, and the gray component replacement is not only to replace the background color with black ink, but also to replace the entire color area of any composite color.

 

(2) Color ink removal range Different background color aging reproduction technology with black ink instead of color ink is limited to the neutral hair area of the dark tone, it acts in a narrow range near the gray axis of the color space. The gray component alternative reproduction method extends the substitution of color inks to the entire color region containing gray components, and its range of action will extend along the direction of increased saturation.

 

(3) The amount of color ink removal with different background color removal of black ink instead of color ink is generally between 30% and 40%, and the amount of black ink replaced by gray components can most vary in the range of 0% to 100%.

 

(4) The black plate with different background color removal is mainly used to strengthen the density contrast of the image and stabilize the middle tone to the dark color; The black version of the grey component replacement reproduction technology not only bears the reproduction of the picture tone, but also participates in the color reproduction of the composite color, that is, the black ink also has the effect of color composition.

 

(4) Background Color Gain (UCA)

Undercolor gain UCA (Undercolor Add Mon) is another plate making process that, contrary to the undercolor removal function, increases the amount of color ink in the darkened area.

The base color gain occurs along the gray axis of the color space, so the effect on neutral gray is greatest and limited to the neutral gray component. The background color gain is controlled by the background color gain intensity and the starting point of the background color gain (from which level of density of the original). It can be used to adjust the gray balance in the dark tone area of the image, and can adapt to the special requirements of the color in the dark tone area, and play a role in increasing the black plate level in the neutral gray area.

 

Background color gain is an effective means of color reproduction by the electric extension, which can be used to eliminate the color bias caused by the insufficient density of one of the three primary colors in the image in the dark, and it can balance the three colors C, M and Y.

 

When SWOP (Coated) ink paper combination is used, the black generation function Medium, the medium dot expansion value is 20%, the black ink limit is 100%, and the total ink limit is 400%, if the base color gain is changed from 0% to 20%, the result shown in Figure 4-4-4 can be obtained. It can be seen from the figure that the color ink is used in the dark area of the image, and when the order value of the image is lower than 75%, the ink ratio relationship is basically unchanged.