For years and years, the primary press control has been Solid Ink Density (SID). In recent years, this has changed dramatically! In every article and every conference, the common theme is running to Delta E (dE) not density. Why? Because SID is NOT a color measurement, it is a measurement of Lightness or Darkness.
That's why you can measure a 100% Magenta patch and you can measure a 100% Cyan patch and get virtually the same values when those colors are nothing alike. Actually, this happened at the recent FTA First-In-Motion (FIM) project! See the image below...
When using dE as the new press control, you are comparing the spectral data of a Reference color to the spectral data of the Measured color and calculating the mathematical difference. (Think of spectral data as the DNA of color.)
There are several products available to use and monitor dE on press, for the FTA FIM project, we used SpotOn! Flexo.
We were able to load in our target reference data, CRPC-6, and using the software see how close we could Colorimetrically match this data.
The SpotOn! Flexo software provides the operator a series of easy-to-understand icons, along with actual data.
- GREEN = Acceptable color Match
- Up or Down Arrows = color match can be improved by increasing or decreasing SID
- Orange or Red Circles = the inks need to be reformulated and cannot be matched on press
The FTA FIM project was a group effort that took a job from concept to completion using FIRST 6.0 methodology printed in 7/color Extended Color Gamut (ECG) on a wide web press.
Once you use dE to monitor color you will wonder, "why did we ever use density?" The fact is, Spectrophotometers required to calculate dE have only recently become commonplace in the pressroom. Prior to that, all we had were densitometers!