15339 ∆E Color Exercise- How to?
Start the Exercise:
In order to determine your color tolerance, the colors on the pages of this exercise were built to display the given delta E (00) differences under a D50 Illuminant. Ideally this viewing environment should be a certified color viewing booth with proper light bulbs. Look at the Purple Rhem indicator on the outside of the Delta E Exercise envelope. This patch should show on continuous color, there should be no stripes visible. If stripes are visible, light is not correct, and Color Tolerance Exercise should not be conducted until the lighting is corrected. If a suitable light booth cannot be used, as a last resort move to a non-tinted window to assess if the stripes disappear. If the stripes disappear, perform the exercise in this environment.
Color Tolerance Exercise Directions
Follow the comparisons starting below. Be realistic in judging whether or not the job would pass or fail based on recent actual jobs. You may want to determine two different tolerances, one for Process Color (higher tolerance) and one for Spot Color (lower tolerance). Process color tolerances are naturally higher then spot color tolerances because process builds are made from multiple ink combinations and spot colors are made from one ink (less variability). Do not judge if you see a difference (you should see a difference between every target), you want to judge where you would “accept” the difference.
#1. Compare
MASTER to LEVEL C
If Acceptable go to #2; If Not Acceptable go to #3
#2. Compare:
MASTER to LEVEL D
If Acceptable, your tolerance is at least 6 delta E; If Not Acceptable, your tolerance is 5 delta E
#3 Compare:
MASTER to LEVEL B
If Acceptable, your tolerance is about 3 delta E; If Not Acceptable go to #4
#4. Compare:
MASTER to LEVEL A
If Acceptable Your Color Tolerance is a 2 delta E; If Not Acceptable, your color tolerance is less than 2 delta E. Caution- these are very tight Tolerances for Print reproduction and without state of the are process control AND color management, you cannot maintain this.
Summary:
Thanks for completing the exercise. Any questions or comments can be directed to David Hunter by email : david@chromachecker.com. This exercise can be customized for any organization wanting to compare known corporate colors within a customized tolerance. Just email details for the customization to david@chromachecker.com for a quote.
How to interpret the results:
The amount of perceived color difference (results of this exercise) needs to be compared with the actual color differences of the devices being used. You will be surprised how different the color of your devices are to one another- it will generally be more then the number your chose in the exercise. You will want to use color targets and comparison software to actually verify how consistent your devices are to themselves over a given page and over time as well as compared to your targeted device.
As with any Quality control project, you do not want to set your tolerance too tight; if you cannot achieve the desired results you will give up the project. Be conservative, evaluate your devices, if they are 5 delta E Peak of difference, then set your tolerance at least 5 if not 6 delta E of tolerance. Over time you will learn what variables are affecting your color consistency and will be able to address them one at a time and as you do you will watch your delta E come down to your goal.
Below is a listing of different delta E values based on your number from the derived exercise. We have attempted to outline what the different tolerances mean from a graphic Arts perspective. The references are to Peak delta E.
