JP2631004B2 - Color scanner zero point setting method - Google Patents

Description

The present invention relates to a color correction for a color scanner,
The present invention relates to a zero point setting method for setting a reference adjustment position for an adjustment knob for gray balance or gradation.

(Prior Art) When a color scanner is newly introduced or standardized, it is necessary to set a zero point for the scanner. The zero point theoretically refers to an adjustment position serving as a reference for accurately reproducing all colors on the document. However, actually, since the adjustment position changes for each document, the adjustment knobs are set up each time. Therefore, the zero point should be grasped as one standard criterion.

Conventionally, when setting the zero point of a color scanner, a transparent color film is used as the original, a halftone separation is actually produced from the transparent original by the color scanner, and both are compared, and a place with good reproducibility is compared. The technique of finding out is adopted. Usually, a comparison between a transparent manuscript and a school print is repeatedly performed by trial and error to find an adjustment position of one reference.

(Problems to be Solved by the Invention) First, it is difficult to determine reproducibility by the conventional method.
This is because the comparison target is a proof print that is a transmissive original and a reflective original, the reproducible color ranges are different from each other, and furthermore, it is necessary to rely on sensible judgment by the naked eye . Therefore, the zero point thus obtained usually fluctuates every time the operator changes. Further, since the proof print varies depending on the printing conditions, there is also a problem that one of the objects to be compared itself is fluid.

Furthermore, there are a large number of knobs for adjusting the color scanner, in particular, the knobs for adjusting color correction, and it is very difficult to understand the effective range or the mutual influence thereof. Therefore, conventionally, there has been a tendency to rely on the experience and intuition of the operator, which has made it difficult to educate a new operator.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is possible to objectively judge a document and an output of a color scanner. The aim is to provide a setting technique.

(Summary of the Invention) In the present invention, a reflection original consisting of a printed matter having a large number of color elements whose dot percentage is known is used, and the reproducibility of a halftone dot separation obtained from the reflection original by a color scanner is determined by the dot percentage. Is determined as a factor to set the zero point.

Since the reproducibility is determined by the common factor of the dot percentage, the determination can be made quantitatively and thus objectively, and an appropriate zero point can be set. Therefore, no experience or intuition is required for the work of setting the zero point, and the education of the operator of the color scanner becomes easy.

In particular, in the present invention, a specific planar color chart is used as the reflection document. The color chart includes a color element for gray balance setting, which is a basis for the balance of three colors of cyan, magenta, and yellow, and primary and secondary color elements for a color correction setting, And a tertiary color element obtained by transforming the color solid into two dimensions.

(Example) FIG. 1 shows a chart for setting a zero point used here.

The zero point setting chart 10 is a printed matter having a large number of color elements 100 formed of four-sided patterns. These many color elements 100 are arranged vertically and horizontally and are divided into several blocks. On the chart 10, first, the tertiary color portion 12
a, 12b, a portion 14 of the secondary color, and a portion 16 of the low-saturation color among the secondary color and the primary color are included. For example, based on a color chart (CCS color chart) according to Japanese Patent Publication No. 61-38465, ten colors are selected for each hue, and there are about 300 colors as a whole. Charts with 300 colors are empirically applicable to various manuscripts,
Its versatility is very wide. The symbols written in the square boxes on the upper and middle rows of the chart 10 are the hue numbers. The denominator indicates the value corresponding to the saturation. These are all based on the display using the CCS color chart. In addition, 1 to 10 to 100 on the right
Numbers in increments of 0 indicate dot percentages.

The above-mentioned part on the chart 10 is used for setting the color correction. The chart 10 further includes the following parts for setting gray balance, gradation, and the like.

Portion 20 marked 3C This portion 20 contains the color components of cyan (C), magenta (M), and yellow (Y) multiplied by the same dot percentage. Halftone percentages are in 10 percent increments.

GB, 30 C, M, Y specified in advance so that the gray balance comes
Is a portion printed with an appropriate film thickness in the halftone dot percentage, and is used for setting gray balance.

Part 40 marked BK The black is composed of 10 to 100% in 10% increments, and sets up the magenta and yellow versions and sets the gradation.

A portion 50 marked as 4C 50 Black has been previously added in consideration of the gray balance of cyan, magenta, and yellow, and the cyan setup and gradation settings are performed.

Paper ground portion 60 White of paper, that is, a portion where nothing is printed, and is used as a calibration point.

Solid black part 70 This is the part where cyan, magenta, yellow and black solids are multiplied.

When setting the zero point of a color scanner by using such a chart 10, first, the range of the color correction effect of the scanner, or more simply, how much correction function each adjustment knob performs for each color Start by making sure you do. This work is carried out in order to know the control function of the adjustment knobs of a large number of color corrections by actually performing color separation using the chart 10, which is a printed matter, as a document. In this case, since the chart 10 as a manuscript is a printed matter, it is important to perform color separation by blurring the focus of the color scanner.

FIG. 2 is a part of a graph showing the effect range of the color correction thus obtained.

In this figure, the hue is shown in the direction of the vertical axis, and the adjustment knob of the color correction is shown in the direction of the horizontal axis (blue violet, cyan, green, yellow, red and magenta are shown in the direction of the horizontal axis. It should be understood that these are color adjustment knobs corresponding to the respective colors.). The effect of each knob, that is, how much the output of the color scanner changes with respect to the dot percentage of the original when the knob is moved fully left and right, is described in the polygon written inside. Is displayed as follows.

Less than 5% change: No indication 5% to 19% change: None Landform 20-50% change: hatching More than 51% change: Solid black Note that polygons are triangular as a whole The arrangement is based on brightness and saturation, as shown in FIG.

In any case, the effectiveness of each adjustment knob of the color correction can be known from the effect width graph of the color correction. Therefore, based on this,
It is possible to produce a separation by a color scanner with good reproducibility, and at the same time, it is possible to systematically perform the work of setting the zero point of the scanner without relying on experience. Also, of course, a certain color, such as a slight change in skin color,
Such adjustment can be easily performed based on the above-mentioned effect width graph.

FIG. 4 is a diagram showing the color reproducibility of color separation by a color scanner set to zero by the conventional method, and FIG. 5 is a diagram showing the color reproducibility when the zero is set according to the present invention. FIG.

In both figures, the horizontal axis indicates the hue and the vertical axis indicates the halftone dot percentage. Regarding the halftone dot percentage, the solid line indicates cyan, the broken line indicates magenta, and the one-dot chain line indicates yellow.
The relationship between the originals is indicated by a thin line, and the relationship between the color-separated images is indicated by a thick line. As can be seen from these figures, in the case of the conventional method shown in FIG. 4, the dot percentage on the document is not accurately reproduced by color separation, whereas in the case of the present invention shown in FIG. Its reproduction is well performed.

Then, when color separation was performed on several types of actual transmissive film originals using a color scanner with zero points set based on the above idea, color reproduction close to the originals was possible. In this regard, another type of color scanner was confirmed, and similarly good results were obtained.

Note that the present invention can be applied not only to adjustment knobs for color correction but also to those for gray balance or gradation.

(Effects of the Invention) In the present invention, when setting the zero point of the color scanner, a specific reflection original made of a printed matter having a large number of color elements whose dot percentages are known is used, and the reflection original is obtained by the color scanner. Since the reproducibility of the halftone dot separation is determined by using the dot percentage as a factor, an objective and quantitative judgment can be made. Therefore, an appropriate zero point can be determined without relying on experience or intuition. Can be set.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a zero point setting chart used in the present invention, FIG. 2 is a diagram showing an example of a graph showing the effective range of color correction, and FIG. 3 is a diagram of a polygon in FIG. FIG. 4 is a diagram showing the reproducibility of color separation according to the conventional example, and FIG. 5 is a diagram showing the same reproducibility according to the present invention. 10: Zero point setting chart, 100: Color element.

Claims (2)

(57) [Claims] 1. A zero point setting method for setting an adjustment position serving as a reference for an adjustment knob for color correction, gray balance or gradation of a color scanner, wherein a number of color elements whose dot percentage is known are provided. Using a reflective original consisting of a printed matter having the above, the reproducibility of a halftone separation obtained by a color scanner from this reflective original, by determining the dot percentage as a factor, by a method of setting the reference adjustment position Yes,
The reflection original is a flat color chart, in which a color element for setting a gray balance, which is a basis of a balance of three colors of cyan, magenta, and yellow, and a color element, which is a basis for setting a color correction, are set. A zero point setting method for a color scanner, comprising: a color element of a secondary color, a color element of a secondary color, and a color element of a tertiary color obtained by transforming a color solid into two dimensions. 2. The method for setting a zero point of a color scanner according to claim 1, wherein when the halftone separation is produced, the focus of the color scanner is blurred.