Home' FLEXO Magazine : February 2016 Contents press). This is exactly the same as if we had performed a “real” press-
run under the hypothetical case that the press prints exactly the same
on the second profile pressrun as the first. As such, a virtual pressrun
is far more accurate than a second “real” profile pressrun.
PROFILE SYNC & THE RULE OF PROFILES
The most basic rule of color profiles (and one that is easily under-
stood) is that your printing conditions for the production pressrun
must match the printing conditions of the color profile pressrun. That
law applies whether you synchronize your profile or not. In the case
that you do not synchronize your profile, it’s the task of the pressman
to try to get the production printing conditions to match those in
place when the profile pressrun was performed. These will be a little
(or a lot) different for each profile—because the press will never hit
the curve specification perfectly during the color profile pressrun. But
if the pressman can achieve conditions that match those of the color
profile pressrun, they will achieve maximum color accuracy.
Synchronizing the profile turns this logic around. It adjusts the profile
(instead of the production pressrun) to match the curve specification
at which the printer is aiming. It’s still the task of the pressman to
match the profile (that’s the rule of profiles), but since all profiles are
synchronized to the same specification, the instructions to the press-
man are simply to match the curve specification. Even if the pressman
is printing jobs that have been converted with 10 different profiles, if
all 10 profiles were synchronized to the same specification, the press-
man’s jobs is simply to print to that specification.
Image 10 and Image 11 show an exaggerated example case of synchro-
nizing the cGyk color sector. In this example, the printer was aiming
its CMYK at G7 and its orange, green and violet at linear Delta E-P.
However, for some reason the color profile pressrun printed with
far more TVI in all colors (Image 10). Instructing the software of the
synchronization aims and clicking the “Apply Synchronization” button
results in a profile which matches its aim (Image 11).
SYNCHRONIZATION APPLIES CURVES ONLY
One final comment that may help to clarify synchronization is to
point out that it is really just applying curves to the profile. The
curves applied are the curves required to alter the “actual” curves in
the profile to match the “desired curves” in the curve specification at
which the printer is aiming. Synchronizing a profile does not change
the solid values, nor does it change the inherent way the individual
inks overprint. To repeat the virtual pressrun concept, synchronizing
has the same effect as performing an additional pressrun with the
correct curves applied and with an exact hit to the curve specification.
Synchronizing CMYK data to G7 won’t produce an exact match the
GRACoL2013.Coated1 data set, but it will produce a data set as close
as you can get with your inks and substrate.
DO YOU REALLY NEED A CURVES PRESSRUN?
The astute reader who fully grasps the concept of synchronizing a
profile to a curve specification may also question the need for a curves
pressrun at all. Given software tools that can extract curves from color
profiles and software tools that can synchronize profiles to a curves
specification, it is not necessary to perform a curves pressrun before
the color profile pressrun. However, unless you have a lot of experi-
ence with EG and can estimate your curves fairly closely for the color
profile pressrun, it is still advisable to perform a curves pressrun first.
Referring back to part one of this article, the best data is achieved
when the color profile press characterization produces printed results
that are fairly uniform in L*a*b* space. Performing a curves pressrun
to derive curves to match any reasonable specification (G7, FOGRA
39, Linear Delta E-P, Linear CTV) will assure a color profile pressrun
with printed result that are fairly uniform in L*a*b* space. This will
reduce interpolation error when this data is used to make a profile or
when the profile is used to convert color.
Smoothed file before synchronization (Image 10, above) and after
synchronization (Image 11, below).
128 FLEXO | FEBRUARY 2016
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