Using Multicolor Test Charts

To create multicolor profiles various test charts (multichannel Photoshop PSD files) with associated reference files are available for measuring in suitable measuring programs. These multicolor test charts can be found in the folder Testcharts (in CoPrA’s installation folder). You can open the folder directly in CoPrA (menu Tools > Open testchart folder…). The contained multicolor test charts are specifically optimized for the algorithms used by CoPrA.

Selection of the correct test charts for your printing process is facilitated by the naming. Therefore, please note the following naming conventions:

  • The name of the test chart contains the number of channels, the color combination and the number of color patches. From the name of the test chart CL-CMYKB-2140 you can therefore deduce that it is a 5-channel test chart with the color combination CMYK+Blue and 2140 color patches.
  • However, by ‘Blue’ we mean a fairly broad color range of reddish to greenish blue. For example, it contains violet as well.
  • For a Hexachrome printing process with CMYK+Orange+ Green, use the corresponding test chart, CL-CMYKRG. Here, CMYKRG stands for CMYK+Red+Green, whereby red includes orange.
  • For 7-color printing use the test chart CL-CMYKRGB. In addition to the colors CMYK it also contains the additional colors Red+Green+Blue.
  • The layout of the supplied test charts is designed to fit on A4 or US letter size. As all patches cannot go on one page the multicolor charts are split in multiple pages which need to be measured in corresponding sequence (1_6 means it is the first of six pages).

 

Important Notes

  • The total area coverage of 400% is not exceeded in any of the test charts.
  • Please make sure that your RIP or the output system of your printer supports Photoshop multichannel PSD files. If this is not the case please open the test charts in Photoshop (or another suitable image editing program) and save them as DCS2 files.
  • The test charts are optimized for the X-Rite i1Pro measuring device, but measurements can also be taken using any single color measuring device and possibly even a measuring table (for example the Barbieri Spectro LFP).
  • If you would like to use a different measuring device, it is necessary to create a test chart which is suitable for that measuring device and the intended printing process. Make sure to select the reference file matching your color system. The reference file is provided by CoPrA and located in the same folder as the test chart files. It can be recognized by the TXT extension and contains all required color patches. Please note that our reference files use a maximum total area coverage of up to 400%, even for 7 channel color systems.
  • For multicolor profiling – in contrast to CMYK Profiling – the test charts has to be adapted to the calculation algorithms in order to minimize color patches, otherwise test charts would be exceptionally large.
    Important: Multicolor profiling differs from manufacturer to manufacturer. If you would like to use measured multicolor test charts from other manufacturers in CoPrA, please note that these test charts may not achieve optimal results in CoPrA.
  • If it is not possible to reprint CoPrA’s test charts and you would like to use existing measurement data from multicolor test charts of other manufacturers, it is recommendable to optimize these measurement data using ColorAnt before creating profiles in CoPrA. The tool Rescale allows to adapt the measurement and reference values in ColorAnt according to suitable CoPrA test charts. Any missing measurement values will be interpolated which may result in inaccuracies if alternative test charts of other manufacturers reveal many gaps.

 

 

Furthermore, CMY test charts are available for printing systems that do not use black.

For example, if you work with CMY+Blue you should use the appropriate test chart from the folder CMY+B. CoPrA uses the measured test charts to create profiles without the need to specify a separation rule. In the case of a CMY+B test chart a 4CLR multicolor profile will be created. Make sure to select appropriate settings for the Black Point of the printer profile: the Mode in the tab Black Generation should be set to Auto.

Note: In the past, many users worked with standard CMYK test charts, such as ECI2002 or IT8/7-4, for color combinations without black, e.g. CMY+Blue, replacing the K channel with blue. Although this approach seems practicable at first glance, it is not that sensible, because the process color black plays an entirely different role to a process color blue in CMYK test charts. Accordingly, many color combinations in the CMYK test charts are unnecessary, or even missing for a blue process color. It is therefore preferable to use CoPrA in combination with CMY+X test charts in order to obtain the best possible profile quality.

This entry was posted in CoPrA4, Introduction and Overview, Load or Measure test charts, Multicolor profiling, Printer Profiling, What's included. Bookmark the permalink. Trackbacks are closed, but you can post a comment.

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