Color label application (two)
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For a pre-sample (whether produced by film or digitally produced) or machine sample, the following methods can be used to effectively measure:
Prepare a densitometer and understand how it is calibrated and operated, which is a basic requirement for measuring color standards. Although the following materials are not used in each color code 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 that can be purchased from GCA.
. To ensure consistency in sample and magazine publication parameters, there should also be a SWOP Hi-Lo patch available from the International Prepress Association (IPA).
· A copy of the dot gain and density checklist. Readers can refer to the relevant samples and collect information to make their own data sheets. When linking the density measurement and visual estimation of a print job, 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, Color Printing, Slides and Photocopying) - The Viewing Conditions standard establishes a lighting system, which is very helpful. Any precise visual estimation of the image of the proof (pre-sample, sample or digital proof) and technical evaluation of the relative color scale are required to be performed under this standard lighting and environment. Note:
. The process of objective and subjective evaluation of color-coded elements only does not require a standard lighting environment.
. Do not attempt to subjectively evaluate objective color-coded elements, such as hue (eg, using a small magnifying glass to detect printed tones to determine total apparent dot gain).
1. Read the T-Ref value on the multi-band densitometer after calibrating the densitometer with reference to the production manual. 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 BackstopTM (a type of master material developed by GCA) or similar material below the color code portion you are measuring. If you plan to place a printed image copy side-by-side with the color-coded portion to be measured for visual estimation, make sure that BackstopTM is not exposed from underneath 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 in the dot expansion and density comparison table (Dot Gain and These measurements are recorded in the Density Comparison Form). The process of measuring the ink on a printed Hi-Lo material is an absolute density measurement, which means that the measurement involves the density of the paper. Do not empty or zero the density meter on the paper surface. When making measurements, place a standard black backing underneath the color block or make sure the color block is printed on a 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 a printed Hi-Lo material is an absolute density measurement, which means that the measurement involves the density of the paper. Do not empty or zero the density meter on the paper surface. When making measurements, place a standard black backing underneath the color block or make sure the color block is printed on a black backing. Also note that papers that support Hi-Lo are not standard paper.
5. Measure and record the paper density with all four densitometer filters.
6. Read and record the measurement values for all channels of the color patch and the portion of the image being measured. Take the absolute density reading for each color element; do not empty or zero the density meter on the paper surface. A channel is a repeating color patch on a color scale; industry members recommend having two repeating color patches on a single page or image color scale. Reading color values in any order is acceptable in each channel. The method used by some automatic monitoring systems prompts the user to measure in the order of yellow, black, black and black, which is a common printing sequence.
7. Read and record the solid ink density in the table and compare it to 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 25%, 50%, 75% color blocks in each channel. The total apparent dot gain value.