Graphics Programs Reference
In-Depth Information
individual gun controls on the display with feedback provided by the
instrument. This is often called
precalibration
, since the idea is to physi-
cally set the behavior of the display as close to the desired white point as
possible. The user will also be expected to set the brightness and contrast
of the display, again using onboard controls and setting the correct values
provided by the Colorimeter or Spectroradiometer.
Once the software and hardware produce the desired precalibration,
a series of color samples or squares are sent to the display from the host
software. The software analyzes the data measured by the instrument and
attempts to continue the calibration process, usually by creating or alter-
ing the CLUT on the graphic card. Once the calibration has been achieved,
additional colors are sent to the screen to be measured so that a result-
ing ICC profile can be built.
All the products briefly covered both calibrate and then profile the
display by building an ICC profile. Most products ensure the profile is
placed in the proper location on your hard drive and set this profile for
use by the operating system (unless told not to). Some of the products
have an option to update the initial calibration instead of starting from
scratch. This can save a good deal of time for those that want to ensure
that the display is in the proper condition. If the calibration doesn't fall
within specification, the software will warn the user or simply conduct a
full calibration and build a new ICC profile. Most of these products will
report any problems with the display when the unit can't achieve the
expected calibration target. This is useful when the time comes that your
display is old enough to go out to greener pastures. Over time, a display
actually will wear out and not be able to produce the desired luminance
levels. One way to get a few more months out of a CRT is to reduce size
of the image using geometry controls. This will “focus” the total energy
into a smaller area. Often the calibration software will report that the
unit is now able to meet the luminance calibration target. It's a good idea
to have a black border about the thickness of your thumb as a minimum
around the display. Don't be tempted to adjust your display geometry as
far as it can go to the edges as this will decrease the color purity of the
image. When a display is past its prime, use it as a secondary display for
all those Photoshop palettes.
There are a number of products on the market that ship with an
instrument (usually a Colorimeter) and software that allow users to cal-
ibrate and profile their displays. I will briefly discuss three such solutions
that are all well-supported products that have been successfully used by
many photographers and color geeks. One of the oldest and most feature-
rich products is ColorVision's Spyder2PRO (formally OptiCAL) software.
This is the flagship software from ColorVision. Spyder2PRO has virtually
every option that even the advanced geek would want in a display pro-
filing package, including the ability to tweak the resulting calibration
curves (don't ever do this!), a reminder when to recalibrate, statistics on
the final calibration, an update calibration routine, and so on. The RGB
