tion inks,” said Bart Fret, director of
large-format sales for GMG Americas.
Dye-sub inks, Fret added, are particularly
problematic. “Th ey are either
printed on paper and transferred under
pressure and heat to the fi nal substrate
or printed direct-to-fabric. Th e transfer
method has many variables, since even
the pressure and speed at which it is
transferred infl uences the colors.” As
we saw in our Fabric Printing Expert
series, any variation across a textile calender
unit can cause inconsistent color.
Finishing can also impact the appearance
of color. “Many materials are
laminated aft er they are printed,” said
Fret. “Coatings and laminates change
the color of the artwork and need to be
considered.”
Th e various applications for wide-format
printing also can create color
management snafus.
“Each media type and application
has diff erent requirements,” said Bryan
Manwaring, director of product marketing
for Onyx Graphics, Inc., “and the
applications are used in diff erent environments.
For example, lighting can
play a large role in the appearance of
color. A vehicle wrap, for instance, may
have outdoor lighting needs that aren’t
necessary in textile applications. Shop
owners must be aware of all variables
and their potential impacts and employ
the right technology to solve them.”
Th en there’s the elephant in the room:
wide-format graphics are big. “Most
large-format and signage applications
can be much larger than what we see
in other printing processes such as
labels, packaging, and commercial print
applications,” said Mark Geeves, director
of sales and marketing for Color-Logic.
“Trying to color-manage billboards or
large-format signage requires more
than just single measurements of two or
four millimeters with an instrument. It
would be better to have large aperture
instruments with the ability to average
measurements or scanning instrumentation
which could average measurements
across a calibration, characterization
(profi ling), or process control patch.”
All of these challenges are enough,
but major wide-format projects or campaigns
can involve the same or similar
graphics printed on some combination
of wide-format technologies, and even
analog technologies like off set. As a
result, the color all has to match, sometimes
down to the nanometer.
Red alerts
Eff ective color management starts
with color measurement, which
usually involves a spectrophotometer,
a device that measures the amount
of light refl ected from a print sample.
Small-format commercial printers
usually have a small spectrophotometer
kicking around, but measuring
wide-format output raises some additional
problems.
“Hardware fl exibility is a key
challenge,” said Jay Kelbley, product
manager for Xrite. “Due to the varying
sizes and formats of output, it can be
important to have a fl exible measurement
device, such as a handheld and
xy, rather than just a page scanner.” An
xy device attaches to a scanning table
that allows for automated scanning
of color swatches or printer output. “A
device that can be used on an xy table,
like with Xrite’s i1i0, but also used
handheld, like an i1 Pro 2, which gives
the user the ability to automate scanning
of color data as well as to take spot
measurements on the printer.”
Some wide-format printers also
have spectrophotometers built into
the devices themselves, which greatly
facilitates measurement.
Orange you glad you
manage color?
Once you have a measuring device,
there are three basic steps to color
management:
• Calibration — Essentially, you print
color patches on your printer/press,
measure the color values you printed,
compare them to target values (i.e., what
they should be), and then let the digital
front end adjust individual ink densities
to compensate for diff erences.
• Characterization — A given ink set
will yield diff erent color characteristics
on diff erent substrates. As a result, a color
profi le (aka an “ICC profi le”) is needed
for each ink/substrate combination. A
color profi le is basically the “correction
data” for a given ink set on a given substrate
Effective color management involves
profiling different ink and substrate
combinations.
on a given printer. It tells the front
end or the RIP how to adjust the ink
densities to get the output to conform to
standard values.
• Control — Keeping tabs on the printer
to ensure that it doesn’t “drift ,” or change
the way it prints color over time, which
can happen.
Another challenge specifi c to wide
format is that color management solutions
are in a kind of “arms race” with
equipment and ink manufacturers.
New ink sets and expanded colors are
Continued on page 25
PrintingNewscom August 2017 Wide-Format & Signage 23