Color elements The color elements are divided into objective color elements (measured by a densitometer or other device) and subject color elements (estimated by the human eye), but not all color labels contain all of these elements. The general color scale contains the following contents.

(1) The objective element 10% hue/high light and high light refers to halftone dots with halftone dots between 1% and 20%. They are some color patches with uniform density, using four colors of cyan, magenta, yellow, and black inks. For printing, these colorimetric values ​​are useful for visually evaluating the platemaking process, because oversensitizing the positive plates will "shrink" or discard these small dots. Using these color patches, you can also measure the value of the highlights when the machine is running. The color standard even contains 3% to 5% of dots.

25% Hue/Quartet These uniform patches contain a dot value of 25% and a more accurate quarter-tone range of 20% to 40%, commonly printed on cyan, magenta, yellow and black. It is sometimes printed with red, green, and blue overprints, and sometimes printed with three- and four-color gray balance elements.

50% Chromaticity / Midtones These uniform patches contain a dot value of 50% and a more accurate halftone range of 40% to 60%. They are commonly printed on cyan, magenta, yellow, and black, and sometimes also in red. Green, blue and overprint are printed, and there are also three- and four-color gray balance elements. Midtones are very important for people to evaluate the quality of images.

75% Chromaticity / Three-quarter Chromaticity Three-quarters of the tone value is important for ensuring a clear and distinct color in a particular printing process. For example, printing with 85% chromaticity in newspaper printing does not produce a print contrast because the chromaticity value is usually printed in the field, so a chromaticity value of 65% or 70% is sufficient when printing newspapers. When selecting the colorimetric value for printing the contrast, a critical three-quarter chromaticity value is to be determined which maintains vivid color under good printing conditions and fullness under bad printing conditions.

The dark tone contains a halftone dot with a color value of approximately 85% or a uniform color block of up to 95% and 98%. This colorimetric value provides a basis for the visual inspection of the platemaking process because overexposed plates fill or block empty areas. These objects can be used to measure in-memory dot duplication in dark areas of the image.

Some color mark manufacturers have piled up highlights and dark spots on a color scale to facilitate rapid detection of extreme halftone dot copying.
Solid Field Solid color patches for each printing primaries can be used to measure solid ink density and calculate dot gain and print contrast. Measurements of these color patches can also be used to estimate chromaticity errors and gray balance of the primary colors, which is helpful in determining the characteristics of the printing process.

Two-color Overprinting Two-color overprinting can be used to measure the accuracy and gray balance of the color shades of green, red, and blue overprints for trap printing.
Three-color overprint Three-color overprint is composed of equal parts of yellow, blue and green dots. It is often used to detect color balance, and it can be printed in a brownish color compared to gray balance color blocks.
Tri-color overlay printing can be used to objectively measure the type of field density printed on the press by three-color printing. The on-site overprinting object also allows for the subjective and objective measurement of the accuracy of the third color overprint on the basis of the previous two colors that have been overprinted.

Four-color black blocks Total dot area coverage refers to the total area coverage (TAC). These values ​​are used to evaluate the total density after overprinting. SW
The OP specifies that the total half tone value of the dark portion during the color separation process should not exceed 300% (Remember: 400% of the field portion in all four-color printing is the maximum value); the color scale required in the publishing field It often includes color blocks with a total area of ​​300%. In general, the combination of tones of this object requires about 79% of cyan, 68% of the product, 68% of yellow, and 85% of black. Instead, for N
on-H ea t A d ve r tis in g P r in tin
g (non-thermal advertising printing) specification SNAP provides that the total network area should not exceed 260%. In the shaded area of ​​SNAP, the color separation values ​​of color separation generally range from 70% to 80% of cyan, 70% to 80% of product, 70% to 80% of yellow, and 20% to 50% of black.

The four-color black block can be used to measure the above total dot area. At the same time, it also takes into account the factors that register shifting at this point on the tone curve.
Sometimes, in the specification that the actual image portion also uses the total halftone area, these color patches are also used as the under color removal. In order to obtain this maximum value, the color separation operator often uses a color separation method to reduce the halftone dot value and remove the color halftone dot value from the dark tone printing area without affecting the visual effect of the shadowed region of the image. .

Color balanced hexagon by B runn e
The color balance hexagon developed by Bruner Systems is an element used to describe the color balance conversion. The hexagon contains gray balance color patches superimposed with 50% cyan, 41% product, and 41% yellow halftone to indicate the smaller dot gain (including unevenness) of the three printing primaries during color conversion. The effect of the expansion of outlets). The hexagonal shape is measured with a density meter, and after special software processing, the dot enlargement values ​​of the three printing primaries can be displayed separately.

(b) Subjective elements Gray balance Gray balance elements are color patches that tend to be neutral gray, resulting from the overprinting of the cyanine half-tone tonality. The color blocks are used to print black with the same chromaticity value, and the degree of change of the gray balance can be visually estimated quickly. Since dot enlargement, double-shadow, reprint, or overprint will cause the change of three kinds of printing chromatic colors, this change can be expressed by the conversion between neutral gray and reddish, bluish, yellowish gray or color.

The gray balance color patches contained in the color scale include various portions of the tone reproduction curve, having a quarter tone, a mid tone, and a three quarter tone.
Visual estimation of dot gain, blur, and ghosting According to the GATF's network expansion point, the 200 lines per inch of the screen's background are divided into ten levels using half tone dot values. These levels of screen background use a uniform 65 lines per inch, with the numbers from 0 to 9 representing the ten levels.

In the printing process, some figures are deeper than the background, and some are lighter than the background. Because the density difference is small, the corresponding density value of one of the numbers will be the same as the background, and the human eye will not be able to detect it. This value shows the relative size of dot gain or dot loss. Higher values ​​indicate higher dot gain, while lower values ​​indicate dot loss.

According to R och es te r In s titu te of Techn o logy (Rochester Institute of Technology) literature, RIT B
u ll's E ye Ta rge
t Designed for checking dot area changes, double shadows, and blurring. This color code is printed in only one color. The color blocks form a concentric ring shape. The outer ring is the thinnest and deepens inwards. The thickness of the outermost layer is related to the screen line of 200 lines per inch. The thickness of the inner layer is related to the screen line of 65 lines per inch.

Dot enlargement and dot loss are shown by the apparent weight change of the printed color patches. Dot enlargement will make the outer portion of the color block darker than the center portion; the extreme dot expansion will cause the outer ring to melt. Loss of dots will make the outer part of the color block thinner and will disappear when it is extreme.

B u ll's E ye shows the dot enlargement in the same direction for two relative darknesses, ie ghosting. The degree of blackening indicates the degree of ghosting. And Bull's E
The black horizontal stripes of the ye color patches indicate the occurrence of blurring