Custom ICC Profiles/Conversion Rending Intents
Custom ICC Profiles/Conversion Rending Intents
- Subject: Custom ICC Profiles/Conversion Rending Intents
- From: Russ Wyatt <email@hidden>
- Date: Tue, 14 Jun 2005 14:14:35 +1000
Hi all color geniuses,
I am hoping some of you can answer some questions that have been baffling me for some time in regards to rending intents when converting RGB files to CMYK.
Q1: Why is it when i convert an RGB image to U.S Sheetfed Coated V2 in Photoshop CS using either Perceptual,Relative, Saturation or Absolute and all with and without Black Point Compensation the black point is always C95 M85 Y85 K85 / Total Ink=350%, but when I convert RGB images to custom made CMYK profiles the black point always changes? I have also noticed the changes with a ISO Web Coated profile from ECI.
I convert all my RGB images using Relative/BLK point comp which gives me the most pleasing results, although I wish the CMYK black point dot percentages and total ink density would be the same as when I convert with Perceptual/BLK Point Comp. I notice that the CMYK black point is different and the total ink density is under or over the total ink density that i set when creating my profiles. I find this is the case for all of my custom icc profiles that I have made using color management products such as ProfileMaker 4.1.5., basICColor print4C, Gretag Macbeth Spectrolino/SpectroScan.
Examples:
Custom ICC Profile(ProfileMaker) - Cromalin 330% - Perceptual/BLK Point Comp: C85 M75 Y75 K95 , Total Ink= 330%. Relative/BLK Point Comp: C75 M59 Y83 K88 , Total Ink= 305% .
Custom ICC Profile(ProfileMaker) - Newsprint 230% - Perceptual/BLK Point Comp: C52 M42 Y42 K94 , Total Ink= 230%. Relative/BLK Point Comp: C67 M62 Y57 K53 , Total Ink= 239% .
Custom ICC Profile(basICColor print4C) - Newsprint 230% - Perceptual/BLK Point Comp: C50 M41 Y40 K97 , Total Ink= 228%. Relative/BLK Point Comp: C48 M32 Y29 K64 , Total Ink= 173% . With basICColor print4C, I selected Relative Colormetric when creating my profiles although I still get a major shift in the black point as indicated in my Newsprint profile, I set the Total Ink Density to 230% but when I convert using Relative/BLK Point Comp I get Total Ink Density of 173%.
ISO Web Coated -
Perceptual/BLK Point Comp: C70 M70 Y61 K100 , Total Ink= 301%. Relative/BLK Point Comp: C82 M61 Y48 K97 , Total Ink= 294% .
Q2: Are all icc profiles that are created with ProfileMaker and basICColor generated with Perceptual Rending in-built in every profile created? Hence why the black point and total ink densities match when converting RGB to CMYK using Perceptual/BLK Point Comp.
Any feed back on these questions would be greatly appreciated.
Kind regards,
Russ Wyatt.
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