How to use Delta-E to determine color accuracy

After we know what is color accuracy and people's requirements for color accuracy, we should know how to determine color accuracy? Generally speaking, in the plate-making and printing industry, people prefer to use Delta-E to measure. This is a measurement method that describes "difference", and it is relatively easy to measure and calculate color accuracy.

What is Delta-E measurement?

In plate-making and printing, most color measurement is done with an instrument, which measures the value of CIELAB (method of plotting color information collected by a spectrometer). The comparison between the colors is done by mathematically comparing the two sets of CIELAB responses, and by mathematically calculating the differences between them. The value used to describe the difference is called Delta-E. Although Delta-E can be derived using arithmetic methods, it is usually described as the smallest difference in color and hue that the human eye can perceive. When describing the differences in the printed samples, the Delta-E value proved to be very effective due to the connection between Delta-E and human perception. In the printing industry, Delta-E between 3 and 6 is generally considered acceptable.

Although the use of Delta-E measurement will be affected by the variability of the observer, ink and medium, but there is a certain allowable deviation, some variability in the quality of ink and paper can be tolerated. But there must always be certain standards. What is standard Delta-E variability? During the operation of the printing press, for the length of time it runs, the sampling interval of good commercial printing should not vary from greater than 3 to 6 Delta-E units.

Generally speaking, the color effects in different Delta-E ranges are different:

1.6-3.2, when viewed from a certain distance, basically no difference in color can be seen, which is usually considered to be the same color;

3.2-6.5, the difference in color can be seen, but the impression of color is basically the same;

6.5-13, the difference in color can be seen, but it can be considered the same hue;

13-25, it is considered to be a different hue. Above this value, it is considered to be a different color.

Based on this, old-fashioned printing presses may experience greater changes than 3 to 6 Delta-E unit values, but regardless of whether this variability is accepted by printers and customers, it should be set up. When a printing job exceeds the company's variability standards, the wisest thing to do is to stop printing and try to determine the cause of the variability. When the cause is determined and corrected, the printing work can continue.