Test Charts and Control Strips
Test Charts and Control Strips
In this chapter, you will find useful information about the test charts supported by Prinect Color Toolbox, what they look like, their use, advantages and disadvantages and other features.
How to Record a Printing Process
The properties of a printing process can be determined by measuring its chromatic features and its linearity. To do this, a test chart is printed with a color scale where the combinations of the four process colors cyan, magenta, yellow and black are systematically graduated, each going from 0% to 100%. Following the proof, this color scale must be measured with a colorimeter and analyzed.
Test charts, often referred to as targets, are reference originals that are used for the characterization of color output devices such as color printers, presses and proofers.
There are different types of test charts, depending on the printing process:
• CMYK test charts are used for profiling printing processes in normal four-color printing with cyan, magenta, yellow and black (e.g. offset and newspaper printing).
The test charts have various graduations of the four primary colors cyan, magenta, yellow and black.
•RGB test charts are used for printing processes with output devices that only support RGB data (e.g. slide imagesetters, desktop printers).
The test charts have combinations of red, green and blue.
•CMY test charts are used for output devices that only print three colors, cyan, magenta and yellow, achieving enough saturation with them to give satisfactory results (e.g. sublimation printers).
The test charts only have graduations of the three primary colors cyan, magenta and yellow but no black.
•Test charts for spot colors (e.g. Hexachrome) are used for printing processes with more than four primary colors (spot colors, HiFi Color).
Test charts were developed for these cases, differing in the number of patches and their layout. Most of the profiling software manufacturers use their own test chart that can only be evaluated with a matching program. In addition, test charts based on international standards were developed such as the ISO 12642 / ANSI IT8.7/3 test charts (ANSI = American National Standards Institute) or the ISO 12642-2 / ECI 2002 test chart.
The drawback of test charts that are arranged in blocks of similar colors (visual layout) is that there are often problems with an uneven distribution of ink.
Since it's not possible for a printing expert to intervene and make specific corrections, there are "scrambled" versions of these charts (random layout, rearranged) where the patches are arranged in such a way that the ink is always applied evenly to the ink zones during printing. However, adjacent colors in these test charts are no longer located beside each other, something that could be visually disturbing when viewing the test charts.
The random version is recommended for characterization of conventional printing processes.
A proof print is made of the test chart matching the printing process that is then measured with a spectrophotometer.
There are test charts with a small number of patches that can be measured simply with a hand-held instrument and others with more than 800 patches (large test charts) where automatic measuring is recommended.
The test chart that you will use for profiling basically depends on
•the profiling software
•the printing process
•the spectrophotometer used
•the profile quality you expect
•the time involved
Test Charts Included in the Shipment
You can invoke the test charts included in the shipment as PDFs with "Programs > Heidelberg Prinect Color Toolbox > Color Toolbox Data" in the "charts" folder.