HCT User Guide
page 8
Copyright © 2001 HutchColor, LLC
User_Guide_43.docx 2/10/19
Scanner profiling
Scanning or capturing the target
Make sure the target is clean and mounted in the same manner as live work. Scan the target without
USM and save it as an RGB TIFF image, with at least 750 pixels in the long dimension, or as
required by your software. Larger files will not increase profile quality. 16-bit-per-channel files may
improve profile quality (slightly), especially if the device’s default response is very dark or light. For
setup tips see the ‘Scanning_Guide’ at
www.hutchcolor.com/CMS_notes.html
. Pay particular
attention to disabling automatic features, fixed end points and optimized tone curve.
Qualifying the target scan
Ideally, every patch in the target scan must contain slightly different values from it’s neighbor
patches. No patch should have RGB values as high as 255 or as low as 0. Failure to observe these
rules may lead to clipping or reversals in the profile.
CCD scanner evenness
Flatbed scanners, especially some 35mm slide scanners, often suffer from uneven illumination
across the image which will negatively affect profile accuracy. To check for evenness, scan a flat tint
of evenly-exposed slide film (about 0.30 to 0.60 density) and examine the RGB values across the
entire area. Variations greater than +/- 002 in either R, G or B across the frame (ignoring dust or
scratches) may be cause for alarm.
Scanner flare
Most flat bed scanners - especially 35mm scanners - suffer from enough optical flare to reduce
profile quality. This happens when light is scattered from neighboring patches or clear areas
surrounding the target. Profile errors due to flare include excessive contrast, plugged shadow tones,
incorrect gray balance and inaccurate colors.
Flare can be detected by opening a typical scan and temporarily setting a high gamma number, like
3.0, in Photoshop. (Gamma is the middle slider in the Levels control.)
Flare in a typical 35mm scanner, with normal gamma (left) and gamma 3.0 (right)
