Graphics Programs Reference
In-Depth Information
if their press and the press across the street were producing the same
color, they would lose the competitive advantage (other than price). This
makes aiming your conversions for such a particular print condition quite
difficult. Once again, aiming for a contract proof helps this issue a great
deal. However, if the press isn't producing SWOP behavior then the con-
tract proof has to deviate as well.
Other organizations that are attempting to set printing standards are
GRACoL
(General Requirements for Application in Commercial Offset
Lithography) and
CGATS
(Committee on Graphic Arts Technical Stan-
dards). These groups, at times, have proposed standards for printing based
on spectral data measured for presses that these groups have set up to a
well-behaved standard they specify. For example, there is a well-defined
specification for SWOP known as
TR001
. The SWOP committee per-
formed a SWOP certified press run that they set up to conform to the
published SWOP conditions. On this press they printed a IT8.7/3 press
test target, discussed in Chapter 6. They measured the target with a Spec-
trophotometer and averaged a group of measured data files. The result
of this work is
SWOP TR001
. This process produced a very specific recipe
for SWOP based on measured empirical data that thankfully anyone with
the hardware and interest can produce and verify. Therefore, TR001
measurement data describes expected SWOP behavior for printing
presses, proofing systems, and separations.
The beauty of SWOP TR001 is the lack of ambiguity. For the 928
CMYK values we have CIELAB values that define SWOP behavior. That
is, if you follow SWOP, and your press, proofer, or separation exhibits
this SWOP behavior, then there will be 928 CMYK values that should
produce specific CIELAB values. If not, this print condition really is not
SWOP. The Adobe-supplied U.S. Web Coated (SWOP) v2 profile conforms
to this TR001 specification. If we were going to send CMYK data to a
press we knew conformed to SWOP TR001, the canned Adobe profile
would produce excellent results. GRACoL has been working on a new
standard called DTR004 for Commercial Sheetfed Printing. This is similar
to SWOP TR001 standards only for sheetfed, not web-press, conditions.
At the time of this writing, DTR004 is still being drafted but at some point
in the foreseeable future, we will have a measurable and empirical
method of defining this sheetfed press condition.
The question now becomes, will printers conform to these standards?
If this were possible, we could all produce CMYK conversions of very
high quality to multiple presses with no need to build our own custom
CMYK profiles. Until that day, the most accurate way to produce con-
versions based upon the somewhat chaotic methods in which printing is
produced is to ask for profiles from print vendors (rarely available), or
build our own. For some reason, some printers will admit they have a
profile for their process but refuse to supply it to anyone outside their
shop, fearing that this profile in some way provides information that
could wind up in the hands of their competitor. This is ridiculous since
