Calibration/Linearization
Calibration reduces the production of non-sellable product by maintaining color consistency from job to job, from one day to the next. Recently, RIP (Raster Image Processors) manufacturers recognized that printers could produce excellent color output, but tend to drift over time, causing consistency problems for users. Most software and hardware RIPs now come with some type of calibration/linearization program. The purpose of these calibration routines is to allow users to compensate for changes in print quality related to temperature, humidity, toner/ink, paper and use over time.
A calibration routine contains a test target, which usually consists of about 20 color patches that range from 0 to 100% ink coverage for each ink color the printer uses (i.e. a 4-color printer would consist of 80 patches). The purpose of this test target is to allow users to evaluate ink coverage. The transition of ink coverage from one patch to the next should be smooth as the ink film thickness increases or decreases. It is very difficult for most individuals to see the ink film thickness differences as more ink is put on the sheet.
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Typical Calibration/ Linearization target |
After printing the calibration target customers have two primary choices to keep their printers calibrated:
1) Output the calibration target and make trial and error adjustments, or
2) Output the calibration target and read the test target with a device that generates density values
These values are then directly entered into the RIP calibration routine. Density values provide a numeric value that correlates to ink film thickness. High density values relate to heavier ink coverage on the sheet, whereas lower density values relate to lighter ink coverage. Most RIP manufacturers have direct interfaces to measurement instruments so that density data can be directly entered into the calibration routine. Most instruments can read the 80 patch calibration target in approximately 5 minutes. The calibration software allows the user to compare the data from the previous calibration to the calibration data that was just entered. The customer then determines, by viewing a chart, if the printer has drifted or needs to be calibrated.
Calibration is important when maintaining critical colors. Examples include colors in company logos, production of multiple prints in a single job, production of various jobs for a customer and matching colors in the reprints of jobs. RIP calibration/linearization programs require density values that can be obtained from Color Savvy’s CM2D Calibrator, CM2C Colorimeter and CM2S Spectrophotometer. Calibration is the foundation of managing color output. RIP and printer manufacturers estimate that 50% of the color complaints they receive are related to issues that could be solved by the implementation of calibration.
The primary reasons that output devices drift after being initially calibrated are related to:
• Temperature changes
• Humidity changes
• Changes in Paper
• Changes in toner/ink
• Changes in screening
• General usage
When should a user calibrate?
• Between rolls of the same paper type
• After changing paper type
• After changing toner/ink
• After changing screen ruling
• Once a week
Why should the customer calibrate their printer?
Savings in Time, Resources and Profits:
•Have the user look in the trash can next to their printer to determine how much productivity is lost due to color problems from their printer.
• Ask the user how much down time they have from calibrating their printer manually with trial and error output.
• Ask how much the user pays for a service technician to calibrate their printer as part of their scheduled maintenance program.
Printer Calibration is the foundation of managing color output. RIP and printer manufacturers estimate that 50% of the color complaints they receive are related to issues that could be solved by the implementation of calibration.
