Summary of ash balance knowledge before the most p

Summary of prepress grey balance knowledge

2. Influencing factors of grey balance

I Ink volume:

yellow, magenta, commercial fishing, and cyan inks all contain mottled colors other than themselves, so you can't overprint with the same concentration of ink to get the concentration you want, which is the impurity characteristic of ink. The change of ink volume will affect the point concentration, so it is necessary to manage the ink volume of the layout, and the method of managing the ink volume is to manage the full page concentration

II Paper:

because the surface material of the printed object will be different, the percentage of dots on the printed object will change, and usually the dots will expand. Because the light will be affected by four factors when passing through the paper

(I) Absorption of ink layers

(II) First surface reflection

(III) Paper reflection

(IV) Multiple internal reflection

III Solid ink density Sid:

the so-called full page density refers to "the maximum concentration of the coloring material on the paper". That is to measure the maximum concentration of C, m and Y inks with R, G and B color filters. When the full plate concentration exceeds a range, the more severe the dot expansion is, the lower the printing contrast is. It will reduce the level of the picture and make the picture lack of three-dimensional sense

ds=-logrs RS rs=10-ds

ds: full plate thickness, such as psf/pbt, psf/abs, psf+ mineral powder

dr: reflectivity of full plate printing ink

rs: reflection concentration

dr=-log (R)

during printing, we need to control the full plate concentration. If the full plate concentration of CMYK is not set, the concentration difference of one of the four colors will be the error of the finished product. The printing factory can effectively control the gray balance by setting a set of fixed full-scale concentrations of four primary colors

IV Dot area Da

(I) Film dot area FDA

fda=1-tt TT: flat film transmittance dt: flat film integration concentration

8. Effective experimental space: 0 (3) 000mm (II) Effective dot area EDA

eda=fda+ (odg+pdg)

odg= optical dot gain

pdg= physical dot gain

(III) Practical dot area PDA

pda=fda+pdg

in color separation and plate making, determine the appropriate dot area of the trichromatic plate, and the appropriate dot area on the overprint depends on the printing conditions. Ps: ulyson equation a=pda, Murray Davis equation a=eda

v Overprint:

the gray part of the three primary colors yellow, magenta, and cyan overprint in the subtraction method cannot be consistent with the original, and there is a lack of contrast in the dark part. The black ink in the four-color overprint can increase the dark part concentration of the three-color overprint, and it can also reduce the cost in the way of gray part replacement (GCR), and it is easier to achieve the gray balance. However, the addition of black version will reduce the contrast, so we should consider whether to use it according to different needs

according to different reproduction needs, the use forms of Black Edition can be divided into three kinds:

(1) because the overprint concentration of the three primary colors is not enough, the first type Black Edition is used to extend the maximum concentration of the reproduction

(2) take the first type Black Edition as an extension, but increase the UCR function, so that the color ink convergence of the three primary colors can only reach a certain level; Increase the ink volume of the black version to replace the three primary colors of the overprint part

(III) the full series blackboard can be divided into two forms, and the difference is that both use UCR

VI Screen lining

the number of points in the unit length of the printed matter. The larger the number of screen lines, the more detailed the performance of the printed matter; The smaller the number of screen lines, the opposite is true. The screen can be divided into glass screen, contact screen and character film, but the contact screen is the mainstream. The shape of contact screen is divided into chain point and square point

different reproductions have different requirements, so there may be different screen lines, which can usually be divided into 65.100.120.150.175.200.300 (lines/inch). The quality of printing is not that the larger the number of screen lines, the better, because more than 2100 college students attend lectures on the screen. The more meticulous the number of lines, the more serious the point expansion may be. Therefore, Mr. Zhang Haohong's master's thesis "Research on the gray balance of screen line number" discusses the neutral color represented by different screen line numbers in the gray balance