Page 122 - Graphic Design and Print Production Fundamentals

110 Chapter 4. Colour Management in the Graphic Technologies
spectrophotometers (spectros), such as the i1 Pro.
The recommended settings to enter for the set-up phase are:

• White point: D65 (6500 K)

• Gamma: 2.2

The setting 6500 K is usually close to the native white point of an LCD monitor. You can choose Native
White Point if you feel that 6500 is too far from the actual white point of your monitor. Gamma is the
tone reproduction curve of the monitor. The setting 2.2 typically provides the smoothest gradients in
monitor display.

Next is the choice of a patch set from small, medium, and large options. This determines the number
of colour swatches that will be projected on screen for the instrument to read. The trade-off is between
calibration time and colour range. Start with the small patch set and see if you are happy with the results.

To start this process, make sure the i1 is on its base plate for the instrument calibration step and then
suspend the spectro in the monitor mounting strap on the monitor. The weight at one end of the strap
hangs behind the monitor to counterbalance the spectro, and the i1 Pro locks into the mounting plate at
the other end of the strap to keep it in place on the monitor screen. The reading aperture of the spectro
should be approximately in the centre of the screen. Tip the monitor back very slightly to help the spectro
sit flat of the front of the LCD.

When you tell the software to proceed, it begins projecting a series of colour swatches that the
colorimeter or spectro records. As you did to produce the measurement file for your output profile, you
are building a comparative table of known device values (the RGB swatches projected on the screen),
with device independent values (Lab readings from the spectro) that describe their appearance. This may
take from three to ten minutes. During this process, make sure that no screen saver becomes active and
you keep the mouse out of the scanning area and. If you leave before the process is completed, check
that the spectro is properly positioned when you return.

Once the colour patches are done, you will be prompted to name and save the profile. Make a habit of
naming your profile with the date so its age can be easily checked. Saving display profiles is similar to
saving output profiles, where the user chooses system and user options. With display profiles, there is no
value in saving previous versions. All you are interested in is the current state of the monitor.

To see the active profile on a Mac, choose System Preferences/Displays/Color. The active profile will
be highlighted at the top of the list. There is a check box toggle limiting the list so only profiles that are
known to be associated with the monitor show.

Input Profiles

As mentioned, we need input profiles when we capture images. There are predominantly two types
of devices associated with image capture: scanners and digital cameras. The fundamental concept in
producing an input profile is that RGB device values scanned or photographed from a target are matched
to device independent Lab values either provided by the target vendor or measured from the target itself.