Page 121 - Graphic Design and Print Production Fundamentals

4.8 Beyond Output Profiling: Display, Input, and Device Link Profiles

Alan Martin

Up to this point, we have focused exclusively on the output profile in our discussion of profiling. This
makes sense, since this is the predominant profile we are concerned with in graphic production. Output
profiles characterize output devices such as printers, proofers, and presses, but there are other devices
that we have to manage in the full spectrum of a colour-managed workflow, and these require two
additional classes of ICC profiles: display and input.

Display profiles capture the colour characteristics of monitors, projectors, and other display devices.
Input profiles characterize devices that capture images such as scanners and digital cameras.

Display Profiling

You may hear this class of profile referred to as monitor profiling, but the more accurate designation is
display profiling to acknowledge the inclusion of components beyond the monitor such as the video card
and video drivers. Though less commonly profiled, this class of profile encompasses digital projectors
as well.

In preparation for display profiling, the cardinal rule of thumb is to make whatever adjustments we
can in the actual monitor. Any software adjustments to the VideoLUT (the look up table stored on the
video card) reduce the operating range of the monitor and limit the spectrum of the display. With the
predominance of LCD monitors, this means that the brightness or white luminance is the only hardware
adjustment available. If you see reference to black level or colour temperature settings, this hearkens
back to CRT monitors where these were actual hardware settings. For LCD monitors, these are software
controls. For an LCD, all light comes from the backlight, which is a fluorescent array behind a diffuser,
so the only monitor control is the brightness of this backlight.

Display profile software typically combines calibration and profiling. A setting called the vcgt (video
card gamma type) tag in the display profile can download settings to the VideoLUT on the video
card and change monitor behaviour. This is an unusual deviation from the standard protocol in colour
management where the profile never alters the behaviour of the device. Calibration is used to optimize
device function and characterization or profiling captures a description of device behaviour. Normally,
the application of a profile should not have any influence on the device function.

Before calibration, it’s essential to warm up an LCD monitor for 30 to 90 minutes. Check the full
brightness. If the monitor has aged to the point where it can’t achieve adequate brightness, then it should
be abandoned as a candidate for profiling. Set the standard refresh rate and resolution that will be used
on the monitor. If these are changed after profiling, then the profile cannot be considered accurate. Clean
the screen with an appropriate gentle cleaner.

When you begin the profiling software, you will be prompted to identify your instrument. Colorimeters
are often provided in display profiling packages, but most software works with standard

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