Gray balance and dot expansion principle (four)
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
3. Calculation method of background color removal
In the analog electronic color separation machine, since the background color removal adopts a suitable image processing method, the neutral gray component in the dark complex color can be separately extracted, so that the ground color removal function can be realized accurately, quickly and simply.
The background color removal is essentially a transformation of the composite color area, replacing the color with black, reducing the amount of three-color ink. Therefore, the calculation method is similar to the black version calculation, but more attention is paid to the color saturation. Usually, the background color removal is limited to The image composite region with small saturation, the simulation operation equation is:
R=S-L-S/K=S-Δ/K
Where: R - represents the amount of background removal L - represents max (Vy, Vm, Vc)
S——represents min(Vy, Vm, Vc)
Δ=L-S indicates the saturation of the composite color, K reflects the degree of influence of saturation on the black plate, and a larger K indicates that the degree of influence of saturation on the black plate is smaller.
In the actual use of the background color removal, it is necessary to take into consideration both the background color removal range and the background color removal amount, and the value range is determined by actual work.
In some electronic color separation machines, the following formula is used to calculate the amount of background removal.
R = removal density / replication density range × 100% = DR / Dr × 100%
Where: DR - removal density
Dr - copy density range
In the background color removal calculation, the K value is usually taken as 5, so that the influence of the convex color on the background color removal is enhanced, and the significant area of the under color removal effect is located at the portion where the original is close to the neutral gray. The background color of the saturated or solid color area is removed little or not, thus ensuring the vividness and vividness of the original picture, avoiding the phenomenon of darkening or winning due to the increase of the amount of black plate, and determining the amount of background removal. At the same time, you need to choose the appropriate background to remove the starting point.
4. Process characteristics of background removal
When the UCR color separation mode is selected, the setting is only the black ink limit and the total amount of ink. Generally, the total ink amount is limited to about 260%, and the black plate starting point is basically fixed at about 50%.
Adjusting the black ink limit and the total amount of ink, the removal amount of UCR will change differently. At the same time, the removal starting point of UCR will also change according to the total ink limit.
UCR is suitable for most originals and printing processes. In particular, the gravure process and the characteristics of the original require bright colors. Therefore, it is more suitable for UCR color separation mode. The black ink limit parameter value can be smaller, for example, 60%, three primary colors. Ink is more advantageous.
The disadvantage of UCR is that the deep primary color with more ash content will be affected by the removal and the saturation will be insufficient. Therefore, when encountering important deep primaries in the image, you need to use the Photoshop tool for local correction to achieve sufficient saturation.
(3) Characteristics of ash replacement (GCR)
Any color separation mode has its characteristics. The technicality of the color separation person is that when selecting the color separation mode, it is necessary to understand its characteristics in order to make full use of its advantages and make up for its shortcomings; it is also necessary to be familiar with the printing expertise and master the characteristics of the original, so as to copy the high quality original.
1. GCR process points
1 Make full use of the black version, do the long-order black version, from 0% to 100%;
2 The gray and black parts in the image are mainly reproduced by black ink, and the gray components composed of the C, M, and Y primary color plates are removed. That is to say, black ink is used to replace the gray and black composed of the three primary color balances in the traditional process to achieve the consistency of optical and visual effects;
3 Replace the ash-containing complex color in the image with black ink, that is, replace the complementary color ink with black ink.
2. Advantages of GCR
1 reduce the total amount of four-color superimposed ink, which is conducive to ink drying and convenient high-speed multi-color printing;
2 is conducive to achieving the balance of printing ash, which can ensure the reproduction and stability of gray tone;
3 Replacing expensive color inks with low-cost black ink can reduce ink costs.
3. Insufficient GCR
1Because black ink replaces the smallest primary color with gray color, the basic color of the color will be reduced, resulting in insufficient depth primary saturation, as shown in Figure 4-4-3.
As can be seen from Fig. 4-4-3, when 20%K replaces the minimum primary color C20%, the basic colors Y and M of the hue are also reduced by 20%. Therefore, the color separation person is important in encountering the original. When using the deep primaries, use the Photoshop tool to deepen this partially darkened primary color to achieve sufficient saturation.
2 Because the long-order black version replaces the complementary color in the color with black, its transparency is more than the complementary color difference, so it has an influence on the vividness of the color, and the black version should be appropriately adjusted.