Graphics Programs Reference
In-Depth Information
Building the Scanner Profile
Once you have found the optimal setting for the scanner driver and
scanned the target, building the profile is a relatively easy process. Vir-
tually every product that can build a scanner profile operates in a similar
fashion. You need to load the scan into the software, crop the target, and
load the associated TDF file. Some products will use the gray ramp on
the IT8 whereas others do not. Most products require the user to locate
the four corners of the target before a profile can be built so the software
knows the boundaries (and thus where the color patches reside). Some
products allow the user to zoom into the image to make this cropping
easier. Some packages will ask you to load the TDF first, which provides
the software with the layout of the target patches.
Whatever the order, the TDF is the necessary measured data of the
target, the software needs to generate a profile. Most products will then
ask the user to name the profile. The software will compare the scanned
data with the TDF and build an ICC profile for the scanner. Figure 4-5
shows the interface for GretagMacbeth's ProfileMaker Pro scanner
module. Here the user loads the TDF (reference data) first, then the scan
of the target. The user is then asked to crop the image. This software
allows the user to skew crop selection if the target has been scanned at
an angle. The software allows the user to zoom into the target, as well
as flip or rotate the target if it was placed on the scanner incorrectly.
Figure 4-6 shows the interface for X-Rite's MonacoPROFILER and how
that software expects the cropping of the four corners of the scanned
target. A useful feature of MonacoPROFILER is the statistic window,
which appears after the scan and reference data have been calculated to
produce a profile (see Fig. 4-7). You could use this window to evaluate
multiple scans and settings for building a profile. Try different scanner
settings, build the profile, and use the one with the lowest deltaE report.
Once you have generated a profile for your scanner, use it on many dif-
ferent originals to evaluate its quality.
Tweaking the Profile by Tweaking the Target
There is a simple technique we can use to alter how the scanner profile
is built if so desired. Suppose after testing the profile on a series of rep-
resentative originals, you find that the profile is in need of minor adjust-
ments. You don't want to resort to using a profile editor, or one is not
available. Let's assume that the scanner profile appears too dark. I open
a scan of a test image with this profile applied. I edit this image in Pho-
toshop using curves to lighten the color appearance. The correction in
this example was input 121/output 141, which lightens the midtones. I
then carefully invert this correction on an adjustment layer. Input would
be 141, output would be 121. This darkens the midtones in the opposite
direction. I then apply this edit on the original scan of the IT8 target. It
