How to measure the color scale For a pre-proofing proof (whether produced by film or digitally) or a machine sample, you can use the following methods to effectively measure:
Prepare a density meter and understand its calibration and operation method, which is the basic requirement for measuring color scale. Although the following materials are not used in each color mark measurement process, in order to further optimize information exchange and process control, it is recommended to prepare the following resources:
· A multi-band Status T density meter;
· A GCA T-Ref, which can be purchased from GCA.
· To ensure the consistency of sample and magazine publication parameters, there should also be a SWOP Hi-Lo color block, which can be obtained from the International Prepress Association (IPA).
· A copy of the network expansion and density comparison table. Readers can refer to relevant samples and collect data to make their own data sheets. When linking the density measurement and visual estimation of printing jobs, you can refer to ANSI PH 2.30-1989—for Graphic Arts and Photography (for printing technology and photography) —Color Prints, Transparencies, and Photomechanical Reproductions (color printing, (Slideshow and photocopying)-Viewing Conditions (observing conditions) standard to establish a lighting system, which is very helpful. Any accurate visual estimation of the image of the proofs (pre-proof proofs, machine proofs or digital proofs) and the technical evaluation of the relative color scales need to be carried out under such standard lighting and environment. note:
· The process of objective measurement and subjective evaluation of color scale elements does not require a standard lighting environment.
· Do not try to subjectively evaluate objective color scale elements, such as hue (for example, use a small magnifying glass to detect the printed hue to determine the expansion of the overall apparent dot).
1. After calibrating the density meter according to the production manual, read the T-Ref value on the multi-band density meter. If the measured value matches the T-Ref value, proceed to the second step. If the two do not match, recalibrate the part according to the manufacturer's instructions.
2. Place a piece of BackstopTM (a master material developed by GCA) or similar material under the part of the color scale you want to measure. If you plan to place the printed image copy side by side with the color scale part to be measured for visual estimation, make sure that BackstopTM will not be exposed under the material.
3. Measure the SWOP Hi-Lo Color Reference (Note: These SWOP Hi-Lo color reference values ​​are only applicable to the magazine advertising market.) Each color block of the Hi value, and the dot expansion and density comparison table (Dot Gain and Density Comparison Form). The process of measuring the ink on the printed Hi-Lo material is absolute density measurement, which means that this measurement method includes the density of the paper. Do not empty or zero the density meter on the paper surface. When measuring, put a standard black backing under this color block, or make sure that the color block is printed on the black backing.
4. Measure and record each color block of the Lo value in SWOP Hi-Lo (Note: These SWOP Hi-Lo color reference values ​​are only applicable to the magazine advertising market). The process of measuring the ink on the printed Hi-Lo material is absolute density measurement, which means that this measurement method includes the density of the paper. Do not empty or zero the density meter on the paper surface. When measuring, put a standard black backing under this color block, or make sure that the color block is printed on the black backing. Also note that the paper that supports Hi-Lo is not standard paper.
5. Use all four density meter filters to measure and record the paper density together.
6. Read and record the measured values ​​of the color code and all channels of the measured image part. Take the absolute density reading of each color scale element; do not empty or zero the density meter on the paper surface. Channel refers to the repeated color patches on the color scale; industry members suggest that it is best to have two repeated color patches on the color scale of a single page or image. Within each channel, reading color values ​​in any order is acceptable. Some automatic monitoring systems use methods that prompt users to measure in the order yellow, magenta, cyan, and black. This is a commonly used printing sequence.
7. Read and record the solid ink density in the table and compare it with the SWOP Hi-Lo value. (Note: These SWOP Hi-Lo color reference values ​​are only applicable to the magazine advertising market.) After measuring the solid density of each channel, also measure and record the 25%, 50%, 75% color patches in each channel Expanded value of total apparent outlets.
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