User's Manual

Digital Proofing: Step by step
38
When making a measurement, the measured Lab values will appear in the Proofed Color column.
Comparing those to the Lab values in the Destination Profile column, CMS will estimate how ‘wrong’
the profile is (due to drift of the proofer, or inaccuracy due to limited resolution), and shift the profile a
little bit to match the measurement , just for this ink. With this ‘shifted profile’ a new match will be
calculated.
After the user has accepted the refined values, new proofs will be made. At this point the user can
decide to do another refinement, because the refined color still is not accurate enough. The option in
the special inks list for the ink to be refined will now be Refined Destination Profile, showing the
refined values. When opening the Color Refinement Tool, the user will see that Destination Profile and
Proofed Color have different values: Proofed Color shows the values obtained in the previous
refinement, while Destination Profile is still the same. Make sure that the patch you are about to
measure was proofed using the refined values.
Why is this important? To make any prediction, CMS must know what ink values were used to
produce the measured color. There is no point in telling CMS that the measured color is very different
from the target color when it was made with totally unrelated ink values. Without this, there would be
no point in multiple measurements.
Why take multiple measurements? CMS may be able to make an accurate prediction for smaller color
differences, but as the difference becomes larger, the prediction is likely to become inaccurate.
Making a first refinement will bring you closer, while a second or even third refinement may correct for
the over- or undershoot of the first refinement.
Note that this workflow assumes that the predicted Lab values for the destination profile conversion
are assumed to be the best match. For out-of-gamut colors, depending on the opinion of the user, this
may not be the case. For this reason, the ‘Custom Values’-based workflow is advised for out-of-gamut
colors.
Refining Custom Values
Refining custom values works somewhat different compared to refining destination profile values.
Here the user manually adjusts the ink values, judging the result either visually or through one of the
supplied ∆E formulas. Values can be edited by clicking the ink percentage you want to modify (inside the black
rectangle). It is also possible to proof grid charts, which are discussed in the next section.
Several precautions should be taken into account when interpreting the result. First of all, even when the monitor
has been calibrated, the colors are not absolute, so only color differences should be judged visually, never absolute
colors. Also, colors outside monitor gamut may seem the same while in reality they are considerably different.
For this reason, an option is available to desaturate the colors so they are all inside monitor gamut. The accuracy of
this desaturation is however limited.
Proofing a Grid Chart
For inks/colors using customized values, a grid chart can be proofed, allowing the user to manually select the right
patch from the proofed output. These grid charts contain patches with different ink combinations that vary around
a central value. The user can specify up to 3 varying inks, and for each ink several parameters can be set: