Home' FLEXO Magazine : February 2016 Contents SAVINGS IN THE MILLIONS?
Synchronizing color profiles provides for the absolute minimum
number of press characterizations over a period of time. For any
change in TVI over time, there is no need to make a new profile. Pro-
viding that the solids values and overprint values have not changed
(i.e. you are using the same ink and substrate), given a synchronized
profile, applying new curves to get back to the curve specification to
which the profile is synchronized is all that is required for a change in
dot gain over time.
Multiple presses pose a similar scenario. If you have 10 presses in a
plant that all use the same substrate and ink, you need only one profile
for all 10 presses. You may use different curves for the different presses
and these may change over time, but making or adjusting curves is
a small amount of work which can now be done with control strip
measurement and does not require a separate pressrun.
MERGING COLOR SECTORS INTO ONE
The very last step in the 7-color profile creation process is to merge
the individual color sectors (CMYK, Omyk, cGyk and cmVk) into
a single, 7-color profile. Good profile creation software does this
SUBSTRATE COLOR (WHITE POINT)
Crucial to a good 7-color profile strategy is the ability to separately
change the substrate color of the profile without having to print a
new color profile chart. In theory, a specific profile will only produce
maximum accuracy for the specific substrate on which it was printed.
It’s also true that substrates vary in both color and printing character-
istics. For substrates that have very similar printing characteristic and
vary only in color, the substrate color can be adjusted digitally, thereby
eliminating the need to make an additional profile.
Profile software that offers the ability for the user to change the sub-
strate color (also known as the white point), then recalculate and save
a new profile has existed for a few years. This worked successfully and
eliminated the need to run many color profile characterization press-
runs, however, it also resulted in a large number of profiles, as well
as confusion as to which is the original. Emerging soon are software
tools that support 7-color profiles and offer the ability to adjust the
substrate color when using the profile (perhaps long after its creation),
thereby eliminating the need to make and store separate profiles for
each different substrate color.
THE FLEXO HIGHLIGHT BUMP
The flexo highlight bump (or highlight “break”) has long been a thorn
in the side of flexographic print quality. This break is the result of the
fact that while a zero percent dot always prints at zero percent, the
first printable dot (say a digital value of 0.4 percent) often prints to
10 percent or higher (in Murray-Davies Tone value). The result is a
visible break followed by darker than desired highlights.
The true solution for the flexo highlight bump is to eliminate it
altogether. Much has been achieved to this end in the last five years
through high definition imaging and plate technologies. But for con-
ditions that still have a highlight bump, it must be accounted for either
inside the profile or when using the profile.
The knee jerk reaction to the flexo highlight bump problem is to just
put a whole lot of highlight points in the profile chart. Even if this
solution worked, it would require far larger profiles (adding an extra
patch at 1 percent would make a nine stage target (2,205 patches) into
a 10 stage target (3,205 patches). And for many reasons, the results
may not be as good as one might expect. To cite just one reason, the
data smoothing that is so critical to producing a good profile will
actually smooth out the highlight break. As you are reading this, re-
search on improved technologies for dealing with the highlight break
is being concluded. The technique of printing a very small separate
target similar to that shown above but for all seven colors (CMYKO-
GV) and measuring just the paper and the first printable tone value
is showing great promise. Like substrate correction, these values can
then be entered into the profile itself (after smoothing) or separately
in the software in the same menu in which the profile is selected.
USING PROFILES IN PRODUCTION
A logical way to conclude an article on 7-color profiles is a brief
description of ways they are used in production. In this section, we’ll
review the making of 7-color tint build books, as well as the conver-
sion of spot colors and CMYK image data.
SPOT COLOR VECTOR CONVERSION
Perhaps the most common task in all of EG printing is the conversion
of spot colors to 7-color process. This is based on the profile. All that
A profile can be substrate corrected if the substrate differs in color but not
printability from the substrate on which the original profile carts were printed.
The flexo highlight bump is the break between the paper value and the first
printable tone. The example here is an extreme case for illustrative purposes.
130 FLEXO | FEBRUARY 2016
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