It is imperative for the press operator to continuously monitor ink densities across the press sheet to verify that the press is printing within prescribed tolerances— “by the numbers,” so to speak.
Identifying these metrics enables press crews to monitor press conditions and adjust ink key settings to correct for any variation as it occurs during the pressrun, resulting in more consistent color for the customer and less waste for the printer.
Color bars support density readings in several ink zones in addition to containing patches that allow for calculation of Tone Value Increase (TVI)/dot gain, print contrast, gray balance, doubling, ink film trapping, and slur.
Anatomy of a Color Control Bar
Available in four-color, six-color, and eight-color versions, the Printing Industries of America Color Control Bars can be output at any screen ruling that your output device supports.
Dual-tier bars contain two stacked 5mm color control bars, while single-tier color control bars include a standard 5mm bar as well as a narrow 3mm version for smaller margin/trim areas.
For convenient use on different size presses, the Printing Industries of America Color Control Bars are provided in three widths, or they may be stepped for large-format presses. All color control bars come in EPS format, and a PDF reference guide of elements is also included with every color control bar. The following patches are common to most of the Printing Industries Color Bars:
Screen tint patches of 25%, 50%, and 75% allow for dot measurement at different points on the tone reproduction curve; TVI/ dot gain and print contrast can also be calculated using these patches.
Solid patches of each ink color are used for measuring and monitoring solid ink densities. Solid ink densities should be run at the values prescribed by the appropriate specifications or standards.
3N Gray Patches
Three-color neutral (3N) gray patches (50% cyan, 40% magenta, 40% yellow) appear next to a 50% black screen tint for reference when evaluating gray balance. The CMY percentages are in accordance with GRACoL®* specifications.
A quick visual analysis of the Printing Industries of America Star Target easily reveals when too much dot gain is occurring or when a directional gain, such as slur or doubling, is present.
Two-color solid overprints of red, green, and blue help evaluate and measure ink film trapping and show the maximum amount of ink laydown possible for the various combinations of process inks.
Total area coverage (TAC) patches allow for measurement of the maximum ink density of CMYK overprints. A 300% TAC patch represents the highest allowable dot area coverage for a #5 coated sheet according to SWOP®* specifications.
*GRACoL® and SWOP® are registered trademarks of IDEAlliance.