Densitometry and colorimetry

Combination for quality

Colorimetry is dominant in prepress

Modern Quality and Color Management systems are based on colorimetric values in prepress. Device-specific profiles of monitors, scanners and proofers, and also output profiles of print standards, are ascertained by colorimetry and transformed into ICCprofile files. Using these files as a basis, it is then possible to construct, exchange and depict true-color digital artwork data. Therefore colorimetry helps with digital production of artwork.

Colorimetry and densitometry for spot colors

With the ICC Standard, like many ISO standards as well, the colorimetric and densitometric values relate exclusively to the process colors CMYK. Here the printer can expect to be provided with inks that fall within a very narrow tolerance band and thus conform to the standards. But this is not the case with special inks, which are often mixed in the printshop. And if it is first noticed by the printer at the press that the special ink does not conform to the colorimetric specification, then the ink must be removed from the ink fountain and the inking unit washed up which is a time-consuming process. No measuring system can mix inks correctly in the press therefore this should be done outside the press before printing starts. The mixed ink should be proofed on a test print device with the substrate to be used for the print run and once it is dry conformity with the nominal value colorimetrically checked with an inexpensive hand-held spectrometer. Prior to starting the run, the densitometric nominal value for controlling the press can be ascertained simply by measuring the test print with the color control unit and then the unit is set to optimally regulate color for the production run. Apart from that, discerning customers can be provided with documented colorimetric values of the print run.

Densitometry regulates the ink film thickness

All color control systems do is open and close the ink slides in order to increase or decrease the ink film thickness on the substrate. However, determining ink film thickness is one of densitometry's strengths. Many of the systems which regulate using colorimetry must first convert the colorimetric measured values into density values. This is an unnecessary step. For decades now, printers have achieved the highest print quality using precise densitometric measuring and regulating systems by manroland - also for spot colors.

Densitometry - reliable whether wet or dry

One major problem with regulating systems that work solely with colorimetry is that as the ink dries on the stock, the color location can change up to as much as Delta E 12. This difference is noticeable to everybody. Which means that inks must be measured wet and dry and sorted so that the colorimetric regulating system can recognize the difference drying makes. With densitometric regulating systems, the predicted change to the saturation or gloss can be simply and reliably simulated by using a polarizing filter. But the standard does not permit a polarization filter to be used with colorimetry.