Application of Reflection Density Measurement and Chromaticity Measurement in Printing (5)

3.34 tone value increases tone value increase

The difference between the upscale value of the print and the upscale value of the film or the tensor value of the digital electronic file. unit:%

Note: The synonym "expanding dots" is only used for halftone dots composed of dots.

4 Technical requirements

4.1 Measurement and Control Bar

4.1.1 Film quality

The quality parameters of the film control strip - such as the density of the center, the width of the edge of the dot, and the density of the sheet should comply with the relevant provisions of GB/T 17934.2-1999.

4.1.2 Minimum requirements for monitoring and control strips

The test strip should include ghost/deformation and printed basic color monochrome ink solid blocks and overprint blocks, namely K, C, M, Y, (C+M), (C+Y), (M+Y), and (C+M+Y) Color blocks. In addition, the control strip should also include at least 3 defined mesh tone control color patches, and indicate the standard gradation value of each printing base color K, C, M, and Y. In the three defined mesh control color blocks, the tone value of one color block should be 20%-30%, the color tone of the other color block should be 40%-50%, and the third block should be 70%. -80%; There should also be a halftone control block that measures midtone balance and a blank block. Repeat this entire test strip as much as possible over the entire width of the print sheet.

The dot shape of the measurement and control bar used for process control should be a circular dot, and the difference between the number of lines and the number of lines of the image should be no more than 10 cm-1. All tonal values ​​(including midtones) should be controlled within 1% of the standard value.

Note: 1 For the control strips with both positive and negative polarity, several control blocks of 10% or more and 90% or more are required.

2 It should be noted here that the control block outlets are designated as circular outlets, and the actual production may be round, square, elliptical, etc., but the designated outlets can check the quality of the entire printing product, printing machine, and enterprise.

4.2 Preparation for Measurement

Make sure the measuring head and sampling aperture are clean. Warm up according to the instrument manufacturer's recommended warm-up time, then calibrate the instrument according to the manufacturer's instructions and set the instrument to the desired mode.

To ensure that the sample is flat and wrinkle free, place the sample on a flat black surface, center the sampling aperture, the aperture should be smaller than the illuminated area (according to ISO 5-4), and the sampling aperture be placed on the control block under test intermediate. Tweak the instrument base and sample so that they are in the same plane.

When measuring the mesh adjustment, the diameter of the circular sampling aperture should not be less than 10 times the width of the cable. For non-periodic halftoning, the diameter of the sampling aperture should not be less than 4mm. If the image element is larger than 30μm, a larger aperture should be used. The area of ​​the non-circular sampling aperture should not be less than the area of ​​the circular aperture defined above.

Note: If the sampling aperture is smaller than the recommended sampling aperture, the average of multiple readings should be taken.

4.3 Measurement of Reflectance Density and Numerical Calculation

4.3.1 Instrument Regulations

Use the densitometer specified in ISO 14981.

4.3.2 Measurement Result Report

Any density measurement report should indicate the exact measurement conditions. The measurement report should show compliance with the requirements of this standard. The report includes the following parameters:

- Density model, name and manufacturer,

- color channels (black, cyan, magenta, yellow, or wavelengths in nm),

- spectral response (should be one of the ISO standard states I, T, E defined in ISO 5-3 or DIN I, DIN E),

- Polarizer (with/without),

- Specimen backing (if not black),

Sampling light hole (mm),

- Relative density value (substrate density is set to 0) or absolute density value - Values ​​related only to the density difference are not required,

- Uncertainty of mixed standards (ISO 15790)