HCT User Guide
page 11
Copyright © 2001 HutchColor, LLC
User_Guide_43.docx 2/10/19
Extended-range profiles
Due to film and development variations, occasional live images may have higher or lower max/ min
dye densities than the HCT, which may result in RGB values outside the range ‘recognized’ by the
profile, and in turn may lead to lost detail in very dark or light areas. An easy way to avoid this
problem is to extend the range of the target scan before making the profile.
Extending shadow detail
If the transparent target
2
has a lower D-max than typical slide film, the scanner profile may fail to
‘see’ very dark shadow details in dark or under-exposed transparencies whose D-max exceeds that
of the target. This problem is greatest in IT8.7/1 targets but may occur to a smaller extent with the
HCT due to emulsion or processing variations. An effective way of solving this is to modify the target
scan to ‘fool’ the software into thinking the target has a wider density range.
NOTE
: This procedure does not truly characterize the scanner at higher densities, but it does increase
the profile’s sensitivity to match the scanner’s maximum shadow sensitivity. Because most scans are
adjusted to optimize the subject, the net result is virtually the same as scanning a longer-range target.
Add an ‘Infinite density’ patch
•
Prior to scanning the target, add a double thickness of blackened film, Silver tape, or some
other highly opaque material in the scan area, to represent infinite black density.
Adding an ‘infinite density’ patch to the IT8 target
•
On the transparent HCT the serial number sticker serves as a handy infinite density patch.
•
Set up the scanner and create the target scan as described earlier.
NOTE
: Because the added infinite density patch may also be affected by flare, the only reliable way to
determine the 'infinite density' response of a scanner with excessive flare is to make a separate scan of
high density black material (e.g. a piece of unexposed slide film) to which an infinite density patch has
been added, then cut-and paste that patch into the edge of your HCT scan in Photoshop. The separate
scan should be masked to avoid any stray light in the scan.
Modify the raw RGB scan
•
Open the target scan in Photoshop and compare the RGB values in the infinite black patch to
those in the blackest step of the target gray scale.
2
This trick is not necessary with reflective targets.
