Building Scanner Profiles - Color Management for Photographers - page 147

nario is a scanner driver that has some setting that allows us to turn off
this auto behavior and set the scanner in a consistent behavior. Since the
scanner driver is fixed, we can profile this condition. The question then
becomes, what is the best, fixed setting in order to produce the best
possible data? This takes some testing on our part since at the very least,
we need to lock down the scanner for white and black points, TRC, and
possibly gray balance. If the white point is incorrectly set, we clip high-
light data. No profile can compensate for such data loss. If the black
point is too low, we don't capture all the shadow detail the hardware is
capable of.
Again, a good profile isn't going to bring back detail that wasn't ini-
tially captured. We need to find the best scanner settings, scan the IT8 or
HCT target, and build our profile. Then we need to keep the scanner set-
tings locked down for every subsequent scan we make using this profile.
This is somewhat analogous to calibrating and profiling our displays. We
would never consider adjusting the controls on the display after such a
process. The advantage to this method of scanning is that we can profile
the scanner and we no longer need to worry about the driver settings.
We have no choice but to leave the driver locked down or we invalidate
the profile. The downside is we are unable to conduct any tone or color
corrections at the scan stage. In essence, we attempt to use color man-
agement to match the original, but if we want to improve the original,
we can't do this at the scan stage (see the sidebar, “Match or Improve the
Scan?”). This means ideally we need a scanner that will deliver more than
8-bits per color since any global editing has to be done after the scan in
Photoshop. We don't want to do this on only 8-bits per color (see the
sidebar, “High-bit Captures”). It also means that if we are working with
very high resolution scans, we have to spend a lot more time waiting for
Photoshop to process the data instead of the scanner driver.
The third and best scenario is using a scanner driver that is fully ICC
aware. Unfortunately, this is somewhat rare. How a scanner profile is
created within these products varies so it is best to read the manuals to
see how the software should be set up to scan a color target. For example,
there may be a menu option that needs to be selected for scanning targets,
which effectively turns off all the scanner auto adjustments. Depending
on the software driving the scanner, find the best possible white/black
and gamma settings to use for creating the scan of the color target. This
ensures the best possible raw data for building a profile. When a scanner
driver fully supports ICC color management, it has access to both the
scanner profile, as well as the display profile, and operates like Photo-
shop. The software doesn't require we lock down the software into a
dumb mode . We can use the tools available in the software driver to alter
tone and color at the scan stage. The previews of the prescan data, and
the numbers provided in the host software info palette match what we
see after creating the scan in Photoshop. My Imacon 848 scanner is driven
by FlexColor software and operates in this way.