HCT User Guide
page 12
Copyright © 2001 HutchColor, LLC
User_Guide_43.docx 2/10/19
Comparing the ‘infinite density’ patch and the darkest gray scale RGB values
•
Subtract the infinite density patch RGB values from the values measured in the blackest step of
the gray scale to get three numbers indicating the R, G and B differences.
•
e.g. (in the example shown above)
Target black –
∞ D
= Difference
R
21 –
3 =
17
G
22 –
3 =
18
B
17 –
3 =
14
•
In Photoshop’s Levels control, enter the smallest or the average of the R, G and B differences in
the top left box, then click OK.
Extending shadow contrast in Levels
Create an ‘Extended’ profile
•
Save the modified target scan with the suffix ‘xt’ (for ‘extended’.) Keep a copy of the original
scan in case you want to modify the amount of extension in a subsequent profile.
•
In the scanner profiling software, use the extended target file to create the scanner profile. Also
build a normal profile with the un-extended HCT in case some originals don’t need expansion.
