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How to Troubleshoot Colour Issues
1. Check Environmental Conditions
You cannot get accurate colour if environmental conditions are out of spec! Digital presses are designed for optimum operation when relative humidity is within the 30%-60% range and it is room temperature. Buy a hygrometer (humidity meter) and thermometer and measure before going to the next steps.
Colour on paper will shift dramatically if there is too much or too little humidity. If paper is not stored in sealed packaging it can absorb moisture when air conditioning is turned off over the weekend. Most complaints occur on Monday mornings in the summertime. Humidity often drops below acceptable levels in the wintertime and must be controlled with humidifiers to get optimal results.
2. Check Digital Press
Download the drum test to check your printer/copier. This file contains one page for Cyan, Magenta, Yellow and Black plus instructions. Examine the output for defects. if there is a defect in one colour replace that drum. Defects all colours will require a service call.
3. Print a Test File
These test files will help you judge how accurately your printer is reproducing colour. You can download the file directly to your RIP to make sure your printer is producing accurate colour. Use the speciified profile with 24 lb Xerox Colour Xpressions.
- GATF Test Form for tabloid paper. Use SWOP profile.
- GATF Test Form for letter paper. Use SWOP profile.
Instructions
Make sure your printer is calibrated before running these tests!
The GATF Test form includes fleshtones, memory colours, tests for highlight and shadow and various colour bars. They gray colour bars are useful for checking gray balance to see if there is a colour cast. You can check for details in the ares of highlight and shadow. The colours bars will show how discrete steps of colour your printer can reproduce.
ISO Test Files
The EFI Fiery rips default to ISO Coated for CMYK jobs. The ISO profiles are developed by the European Colour Initative. The ECI.org web site includes the ISO test files and instructions on how evaluate the the results. Use the Altona Visual test file.
- Altona Test Suite Use ISO coated profile.
4. Check Your Media
To get the best results you must use media that is designed for your toner/ink and paper combination.
You cannot get accurate colour with the wrong media or media that has not been stored correctly!
Paper must be designed for copiers and digital presses. Offset and bond papers will not give you accurate colour. Colour on offset papers can vary dramatically between the front and back side. Some offset papers will not calibrate on digital presses. Contact your paper supplier and ask for digital papers. Paper that has not been kept sealed can absorb moisture or become too dry and you cannot get accurate colour.
Review the Materials Usage Guide (MUG) and Recommended Materials List (RML) for digital press to learn more about using and storing paper.
5. Check Monitor Setup
Many people expect prints to match their monitor. You cannot match every colour that can be displayed on monitor! A high quality calibrated monitor and software that can soft proof will do a better job of simulating print jobs. Software from Adobe and Quark can soft proof print jobs. Office software does not provide any control for colour.
Example of unprintable colours.
Visual Method
Download RGB Calibration file to check your monitor. It contains memory colours, flesh tones and neutral greys. The sky, trees and fleshtones should look natural. The greys should be neutral with no colour casts. If the colours do not look right you need to adjust your monitor. Adobe Photoshop comes with Adobe Gamma to assist in visual adjustments. Use the Ideal method below for critical colour in graphic arts environments.
Ideal Method
You will need a high quality monitor for proofing and calibration equipment. Examples of calibration equipment are the Pantone Huey, Gretag-MacBeth EyeOne Display and Colorvision Spyder. Gretag-MacBeth also offers software for profiling all your devices.
6. Check Software Settings
Software like MS-Office does provide any controls for colour management. There is very little you can do to manage colour with these types of applications.
Graphic Arts software from Adobe and Quark can provide a extensive controls for colour management. The problem in most print shops is that colour management is not setup correctly, if at all. I often find several graphic artists in print shops using different colour settings. Sometimes they have different colour settings for each application! To get good results colour management settings for each application and device must be consistent. If your CMYK profile is SWOP it should be used in each application and on every printing device. Your customers should be tagging their jobs with the profiles they are using so you can accurately convert colours to the working colour spaces you use for your applications and printing devices.
Instructions
In the Adobe Creative Suite open Bridge and check color settings. Make sure the appropriate colour profiles are selected and they are synchronized. In Quark Xpress go to Edit/Preferences/Quark CMS to check your setup.
On your printing devices check the profiles in use to make sure they match your applications and paper and ink combinations.
7. Compare colour in file to printed colour
I often get complaints that the current job doesn't match a previous print job. After investigation, we find out the current job is accurate and previous job or proof is incorrect. The digital press wasn't calibrated when the inital job was printed but the inaccurate print is what the customer saw and is expecting. This is a major problem that can be avoided with daily calibrations.
When the above steps don't fix the problem, compare the colour in the file to the colour on the printed sheet. Sometimes there is a problem with the file, sometimes the printed colour matches the numbers in the file but it isn't what you expected.
Procedure for Pantone colours
Make sure digital press is calibrated before you start. You will need a Pantone swatch book that has both spot colours and CMYK equivalents. Some Pantone spot colours are outside of the CMYK gamut and cannot be printed. Open the file and check the Pantone number for the colour. Compare the printed colour to the Pantone swatch book.
Procedure with other colours
You will need something like a Gretag-MacBeth EyeOne (EFI ES-1000) and EyeOne Share for this procedure.
Measure the colour in the file using the eyedropper or other available tool. Print the job make sure the digital press is calibrated and all the colour profiles/settings are correct. In EyeOne Share you can enter numbers from the file to create a colour swatch. Use EyeOne Share to measure the printed colour. EyeOne Share has tools to calculate the Delta E (the difference) between the two colours.