Building Scanner Profiles - Color Management for Photographers - page 151

dialog appears, the value automatically entered is the correct setting to
rotate the image to strengthen it. Click OK to save the document.

Scanner Settings for Optimal Data

Assuming we have a scanner that is driven by software that must be
locked down, the question becomes, what are the best settings to use?
There are techniques for actually measuring this using an expensive
Kodak ST-34 transparent gray wedge chart. These targets cost several
hundred dollars, and if you feel the need to invest in one and want a
specific technique in evaluating how to set the scanner for optimal behav-
ior, you would be well advised to read www.hutchcolor.com/PDF/
Scanning_Guide.pdf. The other technique is to use the black-to-white
ramp on the IT8 target as a guide for setting the black and white points
on the scanner. The aim is producing the best separation in dark tones
of the ramp while not blowing out the highlights in the whitest step in
the ramp.
Between finding this sweet spot for black and white, setting the Tone
Response Curve or Gamma 1 is key in producing the best scan data. For
film scanners try setting the TRC gamma between 2.2 and 3.0 in incre-
ments of .1 while viewing the RGB values of the white/black and middle
gray values on the target ramp. For reflective scanners, the values will
be lower, around 1.8 to 2.0. It is not possible to specify exact numeric
values, but here are some rough guidelines: Keep the black patch in the
10 to 25 range, the white in the 235 to 250 range, and the middle gray
in the 110 to 120 range. It is usually better to scan flat and then adjust
the highlight and shadows on a high bit-file in Photoshop after the scan.
We want to ensure we can capture the greatest tonal information possi-
ble with the scanner whose dynamic range is fixed. You might find it
faster to scan the IT8 or HCT using a number of settings, using the pre-
vious values as a guide. Then build a series of scanner profiles and apply
each to an image using the corresponding settings used to build the
scanner profile. Visually inspect the effect until you find the profile and
settings that produces the best appearance.
Once the best settings have been determined and a profile built to
reflect this condition, insert the original into the scanner, ensure the set-
tings are locked to reflect the ICC scanner profile, set resolution, and press
the scan button. Since the scanner doesn't understand ICC profiles, the
resulting scanned document will be untagged. The document upon
opening in Photoshop will present the Missing Profile warning dialog.
Select the scanner profile to assign this to the scan and open the image.
You can also set the Missing Profile warning dialog to assign the scanner
profile and convert into your preferred RGB working space in one step.

1

Scanners initially have a linear TRC but in nearly all cases, the manufacturers
use a look-up table to apply a TRC gamma curve to this data. It is this gamma
setting I'm referring to.