ISO 12642-3-2021 pdf free download – Graphic technology — Input data for characterization of 4-colour process printing — Part 3: Extended data set including near neutral scale.
This document defines a data set of ink value combinations that can be used to characterize four-colourprocess printing.This data set is not optimized for any printing process or application area but is robustenough for all general applications. While it is primarily aimed at process colour printing with CMYKinks, it can also be used with any combination of three chromatic inks and a dark ink.
This document is an alternative to the IS0 12642-2 data set where more neutral scale data are desired.lt is not designed as a replacement for ISO 12642-2.
2Normative references
The following documents are referred to in the text in such a way that some or all of their contentconstitutes requirements of this document. For dated references, only the edition cited applies.Forundated references, the latest edition of the referenced document (including any amendments) applies.ISO 12642-2,Graphic technology — Input data for characterization of 4-colour process printing — Part 2:Expanded data set
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:- ISo online browsing platform: available at https://www.iso.org/obp
-IEC Electropedia: available at https:.//www.electropedia.org/3.1
data set
total collection of independently identified ink value sets
Note 1 to entry: The terms “patch” and ” target” are deliberately avoided because they imply a physical object orlayout. T’his document only defines the data values that users are free to arrange in any target layout that meetstheir needs, using patches of any size compatible with their measuring equipment.
3.2
ink values
digital value that represents the amount of a colorant required in a rendering process, which, for thehalftone printing process, is equivalent to the tone value/dot area expressed as a percentage
3.3
ink value set
set of four ink values (3.2) representing the amount of the four colours to be used in a process colourarea
4 Technical requirements4.1 Background
The technical requirements and data set definitions that apply to the data set elements of this documentshall be in accordance with ISO 12642-2.
The key additional requirement that has been identified by the users of the existing target is the needfor more black and near-neutral combinations of C,M, Y ink values. In addition, the use of the visuallayout of the target has diminished with the increased use of automated scanning spectrophotometers.These two factors have allowed the 29 duplicate ink value sets (patches) to be removed and replacedwith 29 new ink value sets (patches) to improve CMY neutral (23 samples) and K-only (6 samples)aspects of printing characterization and profile computation.
4.2Tone value precision
The tone values listed in this document are expressed as whole integer percentages, except for magentaand yellow in the CMY grey scale, which are rounded to one decimal place from the grey balanceformulae in CGATS TR 015[2i1, as shown in Formula (1).
M==0,7470C-4,100×10-4 C2 +2,940×10-5c3
This precision can be important in very light grey patches between 0 and 20 %.
Many commercial lCC profiling software generates printable target images from the supplied lSo 28178text files with 8 bit-per channel precision, which is adequate for most purposes.Printable targets areavailable that have an precision of 16 bits per channel (when integrated by a 3 mm spectrophotometeraperture) thanks to the use of LSB error diffusion when the original 16 bit images were flattened to8 bits.This is the approach taken in the example target in Annex A.
4.3 Data set definition
Table 1 lists the ink value sets that have been deleted from the IS0 12642-2 target and shows the lDs ofthe retained patches with identical values.ISO 12642-3 pdf download.