Page 112 - Graphic Design and Print Production Fundamentals

100 Chapter 4. Colour Management in the Graphic Technologies
size of colour patches and page format, and the size of output will define how many pages are ganged to
a sheet. When prompted, name the pdf with a clear identifier (output device and date or equivalent) and
save it.

Once you have the pdf, use it for any direct output, such as a proofer, or to make a plate for your printing
press so that the colour chart can be printed. In all cases, it is critical that no colour management be
applied to the output device for the production of the chart so that the natural base state of the device
is captured in the colour target produced. It is also essential that the proofer or press be in an optimal
operating state so that the output is an accurate reflection of the device’s capabilities. This may require a
calibration process for a proofer or standard maintenance procedure on the press.

There are several colour chart standards that you should be aware of. The chart produced by your colour
management software will likely be one of these or a slight variation thereof. The original standard is the
IT8.7/3, composed of 928 colour patches. This was followed by the ECI 2002, which has 1,485 colour
samples. There is now an update to the IT8, the IT8.7/4, which has extended the colour sampling to
1,617 patches. The larger number of patches provides a more detailed snapshot of the colour capability
of the device that you are profiling. Of course, it takes more time to read the greater number of samples,
so the newer sets are more manageable with automated reading devices such as the iO table. If you are
reading with a hand-held spectro, choose the IT8.7/3 or smaller patch set if it is offered by your colour
management software. The other trade-off between larger and smaller numbers of colour patches lies in
the smoothness of colour transitions. Fewer data points mean less interpolation and potentially smoother
curves in colour modulation. Be aware that it will require some experimentation on a device-by-device
basis to determine the ideal intersection of accuracy and smooth interpretation for your measurement
data.

The colour charts come in two standard patterns of organization: random and visual. Random is exactly
that, and comprises the vast majority of charts that are produced for measuring. The colour swatches
are distributed to provide optimal contrast between adjacent patches to aid the spectrophotometer that is
reading them in distinguishing where one patch ends and the next begins. Having the colours scattered
over the sheet also generates relatively even distribution of cyan, magenta, yellow, and black ink which
leads to better performance from the press. The visual pattern places the colour blocks in a logical
and progressive sequence so it’s easy to see the chromatic ranges that are covered. Some scanning
spectrophotometers can read the visual arrangement.

Measuring Your Colour Chart

Once you have used the pdf to generate the printed sample, you have to measure the sample. For charts
from proofers, it is critical to wait a minimum of 30 to 90 minutes after the sample has been produced
before measuring in order for the colour to stabilize. To create a measurement file, you need three things:
colour management software; a target from that software; and a measuring instrument supported by the
software. After connecting your measuring device to the computer (remember to connect directly to a
USB port on the computer, not to a peripheral such as a keyboard), enter the measuring step of your
colour management software. You will need to point to the correct measurement chart that was used,
which can be easily identified if you have named it distinctively, and confirm the right measuring device
is indicated. If you are getting errors once you begin measuring and can’t proceed, the typical culprit is
the selection of an incorrect colour chart or incorrect measuring device.