Heidelberger Druckmaschinen Ag

Linotype-hell Ag

Günter Bestmann

Manfred Jurkewitz

Helmut Siegeritz

Jürgen Rautert

A method for calculating characterization data of a printing process, is more manageable and less complicated than previously-known methods, in which determining printing tables for CMYK printing systems with special colors or for multicolor systems easily becomes unwieldy and complicated because of necessary colored areas in test elements. A test element supplies actual spectral data. By using subsets of this actual data, tonal value curves or tonal value gain curves, parameters of a model of the printing process for determining spectra of overprinted printing inks and adapted input variables, are determined in a calculating device in accordance with the model, taking into account the tonal value gain, to determine corrected tonal values or their spectra. Then only a few colored areas are needed to calculate characterization data. A test element for determining characterization data of a printing process and an apparatus for carrying out the method are also provided.

Method and test element for determining characterization data of a printing process and apparatus for carrying out the method

In printing processes, even when a process calibration under predefined printing conditions is used, it is possible for deviations in the gray balance to occur. Attempts have been made to correct the deviations, for example by changing the layer thickness of the printing inks in the printing process, but that can lead to color deviations in other regions. A gray balance correction method with which wastage that regularly occurs can be reduced and an occurrence of undesired color fluctuations can be avoided, is achieved by using differences between black and chromatic gray areas in gray balance areas to replace the measured values from a first process calibration with corrected measured values and carrying out a new process calibration.

Method for gray balance correction of a printing process

A method and a system for producing a printing form for a printing process on a printing press, produces a first printing form based on first image data and prints a printing image on a printing substrate with the printing form. Printing presses without inking zones do not permit regulation of quantitative ink supply with inking zones screws. To permit a printer to manipulate ink density on a printing substrate even after exposure of a first printing plate within a printing press without inking zones, correction values are generated in the vicinity of the printing press in regions on the basis of at least a printing image printed on the printing substrate. The correction values are then used for correcting printing originals on which printing is based and/or screened image data and at least one second printing form is produced on the basis of at least the correction values.

Method and system for producing printing forms for anilox printing presses

A method for correcting gray balance of a printing process includes imaging printing forms assigned to color separations with a test form, printing a printing material using the printing forms in a printing press and calorimetrically measuring the test form printed onto the printing material. It is undesirably possible to produce a new color error in other tonal value ranges due to changing the layer thickness of a process ink to correct the gray balance. In order to perform a gray balance correction without disruptive secondary effects, a test form is imaged with colored gray areas, after their colorimetric measurement, at least two of the colored gray areas are selected and, based on their color values, a corrected tonal value of a non-black chromatic process ink is determined, and this corrected tonal value is recorded as a corrected set point of the process ink for imaging following printing forms.

Method for correcting the gray balance of a printing process

A method for producing a proof, having proof printing inks cyan-P, magenta-P, yellow-P, black-P, for an edition printing process, and primary printing inks CMYK and a secondary printing ink RGB, converts edition printing process printing inks with association tables into proof printing process printing inks, for combinations of input color components, associated output color components being stored in the association tables. Reducing storage requirement of association tables having &#x3e;four input color components is done by dividing into a plurality of association tables. Up to four printing inks are printed in the edition printing process during color separation for the edition printing process by GCR and CCR application. Factors of gray and color component replacement are chosen as a function of chroma of a color to be printed. CCR is applied only to a color to be printed to which a GCR with a factor of 100% has already been applied.

Method for producing a proof for a printing process having more than four printing inks

A method for transforming device dependent color values [C1, M1, Y1, K1] of a first printing process into device dependent color values [C2, M2, Y2, K2] of a second printing process, the printing processes being characterized by color profiles setting the device dependent color values of the printing processes in a relationship with the device independent color values of the LAB or XYZ color space, includes determining, from the profiles of the printing process, a one-dimensional assignment function K2=f(K1), and describing the paper white of the first printing process by the color values [C2pw, M2pw, Y2pw, K2pw] of the second printing process. Pure gray colors from the first printing process having the device dependent color values [C1=0, M1=0, Y1=0, K1] are transformed into the device dependent color values [C2pw, M2pw, Y2pw, K2pw+f(K1)] of the second printing process. The assignment function is determined from the lightness curves of the first and second color profiles that, in each case, apply to printing only with black printing ink.

Method for the printing-process transformation of the color print for black/white images

Spot colors are reproduced with a combination of the primary printing inks cyan, magenta, yellow, black and at least one secondary printing ink red, green, blue. A first test form is printed with the primary printing inks and measured calorimetrically. Further test forms, in which one of the colored primary printing inks is replaced by a substantially complementary secondary printing ink, are printed and measured calorimetrically. An International Color Consortium (ICC) color profile is calculated from the measured data of each test form. For each spot color to be reproduced, the proportions of printing inks of the ICC color profile achieving the lowest deviation between the spot color and the reproduced color are determined. The printing ink combination belonging to that ICC profile is selected for the reproduction of the spot color. It is possible to reproduce as many spot colors as desired with four primary printing inks and a maximum of three secondary printing inks.

Method for the reproduction of spot colors with primary printing inks and secondary printing inks

Method and apparatus for the conversion of color values

The invention is directed to a method and to an apparatus for the calibration of color values in color conversion in apparatus and systems for image processing. Measured color values of an apparatus-dependent input color space are acquired by scanning a suitable test original with a plurality of color fields in an image input apparatus. The measured color values are transformed into color values of an apparatus-independent communication color space in an input color converter on the basis of an analytically approximately calculated conversion table. The approximate calculation of the conversion table occurs taking the pre-distortion of the measured color values and the spectral properties of the respective input apparatus into consideration. The transformed color values are compared to the colorimetrically defined color values of the test originals that are measured, for example, with a spectral photometer. Correction color values for the three-dimensional conversion table of the input color converter are calculated from the color value differences, the calculations being on the basis of an error compensating calculation.

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Altenholz, Germany

Günter Bestmann