CMYK Printing Research Articles

Print Quality of Coated Paper from Invasive Alien Plant Goldenrod

When designing products with a shorter lifespan, such as packaging and graphic products, sustainability and circular economy are particularly important. The use of an alternative fiber source for papermaking, such as collected biomass from invasive alien plant species (IAPS), is a good example of sustainable natural resource management, where IAPS are seen as a potential source of various new products. The aim of the present study was to analyze the printability of paper made from the IAPS Goldenrod. CMYK prints were made using inkjet digital technology, and their print quality was determined. IAPS Goldenrod paper, with its natural brownish color, low gloss, high voluminosity, high surface roughness and porosity, shows inferior print quality compared to recycled office paper. In order to improve the printability of this paper, surface coating using three different wet film depositions was applied. The results indicate that the smallest coat weight used suppresses the color and inferior properties of IAPS Goldenrod paper efficiently, resulting in similar printability for both the analyzed papers. Only a small difference in print quality between coated IAPS Goldenrod and recycled paper was determined, suggesting that low-value, non-demanding graphic products and packaging could be made from the coated IAPS Goldenrod paper.

An Application of Deep Learning Technology in The Recognition of Forged Documents with Color Laser Printing

<p>Advanced laser printing technology is now widely used in daily life and at work. Because laser printers are so easy to obtain and use, they have also become a popular method for criminals to forge important documents like currency, securities, and certificates. To obtain evidence for document forgery, traditional forensics use chemical analysis of ink, but the cost is high. Laser color printing uses halftone technology. This technology combines the CMYK printing colors’ halftone screens at their respective angles. When correctly superimposed, they will form a moiré pattern. And the moiré pattern of a color block differs depending on the printer brand or model. This paper will use deep learning to create an image recognition model that can quickly classify forged documents by combining image processing, data augmentation, and transfer learning. The experimental results are examined using indicators of accuracy, precision, recall, F1-score, and PR curve. The results show that ResNet-50 has the best performance and can be used to detect document forgery. The study’s findings will be useful for future criminal investigators and forensic personnel in their work.</p> <p> </p>

Optimizing the Spectral Characterisation of a CMYK Printer with Embedded CMY Printer Modelling

In the digital printing process, reliable colour reproduction is commonly achieved by printer characterisation, which defines the correspondence between the input device control values and the output colour information. The cellular Yule–Nielsen spectral Neugebauer model, together with its variants, is widely adopted in this topic because of its superb colorimetric and spectral accuracy. However, it seems that current studies have neglected an inconspicuous defect in such models when characterising printers equipped with black ink. That is, the cellular structure of these models overemphasises the sampling for dark-tone colours, and thus leads to relatively large errors in light tones. In this paper, taking a CMYK printer as an example, a simple and effective solution is proposed with no need of extra sampling. With the aid of a newly built cellular spectral Neugebauer model for the embedded CMY printer, this approach optimises the printer characterisation for light tones, slightly improves the precision for middle tones while it maintains the accuracy for dark tones. The performance of the proposed method was evaluated with regard to three different kinds of substrates and the experimental results validated its improvement in spectral printer characterisation.

How to print a rainbow

In the 17th century Isaac Newton demonstrated that white light consists of the superposition of different wavelengths visible as colour on a screen. How colour was perceived by a human observer was explained by the work of Thomas Young and Hermann von Helmholtz who identified three cones in the human eye as responsible for colour perception. James Clerk Maxwell succeeded in capturing colour on black and white film by taking photographs through RGB filters and then projecting the positive slides through the same filters again. On white paper the RGB recordings are usually translated into CMYK prints. We will discuss the difficulties in capturing and reproducing true colour using as an example completely analogue photographic methods as used by Sergei Prokudin-Gorsky in the early 20th century and showing how colour perception is affected by the recording method, development of the film, the spectrum of the printing inks and the colour of the substrate.

Multi‐wavelength excitation method for measuring FWA‐treated paper

AbstractColorimetric properties of fluorescent materials depend on the SPD of the illumination. That is why most standards for evaluating them specify the illuminations, which are often hard‐to‐realize daylight illuminants. The presented method using commercially available LEDs enables accurate enough colorimetric measurements of FWA‐treated papers or prints on them illuminated by the specified illuminant. The total spectral radiance factor of a fluorescent specimen, from which most colorimetric values are derived, consists of the luminescent spectral radiance factor and the spectral reflectance factor. This method separately estimates those of FWA‐treated paper to add up to the total spectral radiance factor. The luminescent spectral radiance factor is obtained by estimating the SPD of luminescence excited by the specified illuminant as the weighted sum of the multiple SPDs of luminescence excited by the respective narrow band LED emissions at different wavelengths. The LEDs and their weights are determined optimally for generally used papers. The spectral reflectance factor is derived from the estimated SPD of the radiation with fluorescence excluded from the paper illuminated by visible illumination. The method was applied with five different illumination systems each using two or three narrow band LEDs in the excitation range. They were evaluated by measuring the total spectral radiance factors by D50 of seven FWA‐treated papers and CMYK prints on four papers. The derived colorimetric values were compared to the respective references by the ideal D50.

Printing Quality Enhancement by Detection of Printhead Defects In Single-pass Inkjet Printing

Banding and doubling are two of the most common problems in inkjet printing, which are caused by printheads defects including blocked nozzle and poor registration. It is expensive and inefficient to solve the problems by enhancing device accuracy or replacing the defective printhead, since the device or printhead may degrade over time. In this paper, we propose an economical and efficient method for banding and doubling reduction by detection of printhead defects without requirement of hardware renewal. We design a test pattern composed of specially organized dots to diagnose status of each nozzle by image processing. Specifically, after analyzing the printed and scanned test pattern, halftone images are modified according to the detected information for banding and doubling reduction. We adjust the size and placement of dots based on human perception in order to improve the printing quality. The detection and reduction are carried out in CMYK printing colorant channels separately. Thus, it could overcome the inter-channel interference which may affect the detection accuracy. Experimental results show that the proposed technique is flexible, highly precise and has extensive self-adaptability for various devices, halftone styles, substrates and inks.

Image Transformation for Digital Printing Machine

A computer monitor through mixing shades of red, green, and blue show pictures, that is named RGB color model. CMYK use the different color reproduction technologies and properties. A CMYK printer instead uses light-absorbing cyan, magenta and yellow ink. This paper discusses the conversion between RGB and CMKY color model. OpenCV was used for the verification of the effectiveness of the algorithm is proved to be feasible.

PRINTING.Natural zeolite as filler in base ink jet paper sheet

Abstract The aim of this research was to investigate the influence of natural zeolite clinoptilolite used as a filler on the printabi1ity of paper and its print quality. Paper handsheets were prepared with the addition of 20% of fillers, where natural zeolite was added to calcium carbonate in different u.w.% (i.e. 20, 40, 60). Zeolite originates from the sedimentary deposit in Donje Jesenje, Croatia. Zeolite tuff is mainly composed of clinoptilolite. lts particle size distribution is broad and the structure is micro- and mezzo-porous. The addition of natural zeolite as a filler resulted in higher bulk of paper sheets and a more porous structure. Moreover, the absorption capacity and the absorption rate slightly increased. The surface roughness increased, leading to a more hydrophobic surface. Natural zeolite with its broad particle size distribution, higher amount of large particles and yellowgreen colour resulted in slightly lower opacity and ISO brightness of sheets. When used for ink jet printing, the increased amount of zeolite showed a positive influence on the print quality. Smaller wicking and bleeding effects were noticed. Paper hue did not influence the colour density of CMYK prints.

Press Characterization Recalibration by Principal Component Analysis and DEBP Model

Artificial neural networks (ANN) combined with PCA are widely being used. This study addresses the problem of updating a CMYK printer characterization in response to systematic changes（printing material, press）in device characteristics with PCA-DEBP model. In this study, training samples of test chart, which were normalized through principal component analysis (PCA), were applied as inputs to a differential evolution back propagation (DEBP) neural network with one hidden layer. This DEBP model has been used to predict the present printing characterization using the last ICC profile by measurement with high convergence speed. Experiment results show that the predicted printing characterizations compare with that by the measurement has little color difference. So a PCA-DEBP model can be used to exactly recalibrate the ICC profile over time with low cost.

Comparison of ultraviolet inkjet printing on different synthetic fibrous papers

We investigated the printability of fibrous synthetic papers with ultraviolet (UV) inkjet technology. Cyan, magenta, yellow, and black (CMYK) color fields were printed on two types of fibrous synthetic papers using two different wide-format UV inkjet printers. Spectrophotometric and densitometric measurements were performed on CMYK color fields with different ink coverages, along with a microscopic analysis of unprinted paper, black prints with 100% ink coverage, and a print mottle of magenta and black prints. Colorimetry and optical densities of the CMYK prints were qualitatively and quantitatively compared. Color deviations in CMYK prints were affected by paper type and were dependent on the UV inkjet printer used.

Infrared hidden CMYK graphics

The article presents a further development of new method of carrying out security graphics by programming color mixing for two separate wavelength areas. The first image is observed in daylight only, and the other image is observed separately under infrared (IR) light. Two independent graphics, two different pieces of information may be texts, vector or pixel images, and graphics generated by algorithms. Both images are printed simultaneously with CMYK printing inks only. In the near infrared range there are significant transitional phenomena that were not researched and targeted or applied. Many new measurements have been conducted describing the general relationship to set a new separation theory that has the goal of introducing the properties of infrared light in the reproduction of images. Targeted creating of two images is supported by the method of detecting their authenticity. The proof of the original print includes the characteristic of CMYK working spaces being device dependent. The application is in the security area on all graphic products, securities, documents, printed matter, packaging material, plastic products, works of art protection, product declarations, textiles and leather security, including brand protection.

Optical and Color Stability of Aged Specialty Papers and Ultraviolet Cured Ink Jet Prints

The present study deals with the optical and color stability of aged specialty papers and ultraviolet cured (UV) ink jet prints. As paper substrates, a fiber synthetic paper and two types of lignin-free papers with included security elements were used. Prints of CMYK color fields using UV Curable Inks were made using a UV ink jet printer, Océ Arizona 250® GT. Samples of papers and UV ink jet prints were artificially aged using standard techniques of accelerated aging, such as moist heat (80°C and 65% RH), dry heat (105°C) and treatment with the a xenon arc lamp (35°C CT, 50°C BST, 35% RH). Aging was performed for periods of 1, 2, 3, 6, and 12 days. In this study, optical properties of untreated and treated paper substrates such as the whiteness and yellowness index and color differences between untreated and treated UV ink jet prints were followed. The tested paper substrates behaved differently. The fiber synthetic paper was more stable than both lignin-free cellulose papers. Some color differences during accelerated aging were observed in prints. The effect depends on the particular ink and type of accelerated aging. On average, dry heat treatment and treatment with the xenon arc lamp showed greater impact on CMYK prints than moist heat treatment. The most stable among the prints was the black ink.

CMYKIR security graphics separation in the infrared area

Graphic printing inks respond in different ways when they are in the wavelengths of a near infrared (IR) area. It is not possible to measure such response in the IR and describe it with parameters from the CIELab, sRGB or HSB color systems that are the base for color theory in the visible spectrum area. Additive RGB colors that we use to describe the image in our eye correspond with subtractive C 0 M 0 Y 0 printing inks used for nearly overall printing reproduction in the overall color visual spectrum. Adding of black color ink that has a good response in the infrared area, and subtracting CMY inks makes it possible to carry out each color tone in an endless number of ways. CMYK printing ink characteristics are the basis for setting the algorithm for double appearance of independent graphics: the first graphic in daylight and the second “IR graphic” in infrared light. Proposed algorithm creates a print X on the base of two pictures: the original one X 0 and mask F. The aim is documents’ ultimate security which is detected in IR area. Graphic element visibility with the help of instruments in the wavelength area from 700 to 1000 nm allows programming the selection of image information by using process inks only. The individual characteristics of those printing inks are used for introducing a new criteria in the RGB/CMYK separation process with the goal to create IR graphics. We call this separation CMYKIR and use it for planning the dosing of inks in the creation of good quality reproductions with incorporated IR characteristics: either for causing or prohibiting the IR effect. The goal of CMYKIR reproduction is to incorporate the set “IR graphic” that is not meant to be detected in the visible spectrum part.

The durability of UV ink-jet prints on special papers upon accelerated ageing

The aim of research work was to investigate the influence of accelerated ageing on unprinted and UV ink-jet printed special papers. Prints with CMYK color fields were made by UV ink-jet printer Océ Arizona 250 GT on three types of special papers; a fiber synthetic paper, a woodfree paper with included invisible security fibers and multitonal watermarks and another woodfree paper with security elements. On unprinted and CMYK printed special papers the moist heat treatment at 80°C and 65% relative humidity was performed. Samples were aged according to the standard ISO 5630:3 for 1, 2, 3, 6 and 12 days. Attention was focused on the investigation of the optical properties of papers (i.e. whiteness, opacity and yellowness) and colorimetric properties of CMYK prints during moist heat treatment. The properties of CMYK prints were determined with the measurements of CIELAB values before and after accelerated ageing and on the bases of those measurements the color differences have been calculated. The analysis revealed some deviations between CMYK prints and papers. The best durability upon accelerated ageing obtained the fiber synthetic paper and the black ink prints at all three types of paper.

Characterization of High-Fidelity Color Printing Devices Using Illuminant-Independent Approaches for Color Imaging Application

The aim of this research was, optimally to derive a multi-spectrally illuminant-independent type of High-Fidelity (Hi-Fi) multi-color printing device characterization model, which could reconstruct spectra of every color concerned in high-dynamic-range of original images for an accurate color-matching or - reproduction application. In this study, the Adobe RGB color space under the D50 illuminant condition was used as the reference working space. To have the ability to adapt the change of light sources, two works were preliminarily carried out. Firstly, an ideal type of CIEXYZ camera characterization model was derived using a spectral reconstruct method, based on basic vector under the D50 condition. Via the estimation and the reconstruction of the spectrum of every pixel in question, the XYZ under any light source considered could be obtained accordingly. Therefore, any Adobe RGB format of Hi-Fi complex color images could be transformed into the multispectral type of images via the CIEXYZ camera model derived. Secondarily, the characterization of 7-ink CMYKRGB printing process, using FM screening technique, was implemented and tested in terms of single stimulus. The superset of CMYKRGB i.e. Hi-fi color set) was divided into seven 4-ink groupings, including KGCB, KBMR, KRYG, RKYM, GKYC, BKMC, and also CMYK. Each subgroup contains three chromatic inks and one black ink. Both the multispectral (MS, i.e. narrowband) and the broadband (BB) types of characterization models, using 3rd-order and 2nd-order polynomial regression equations respectively, were developed in this stage. They all applied singular value decomposition method (SVD) and constructed including both transforms of forward (i.e. fractional dot area (FDA) to XYZ/L*a*b*) and reverse (i.e. XYZ/L*a*b* to FDA) processes for each subgroup. The transform between device-independent data and device-independent data was derived and defined via measuring a number of colors in the IT8.7/4 training/test target produced using each 4-ink grouping subset. An approach of key component replacement (KCR), which is similar to GCR (gray component replacement) applied in traditional CMYK printing process, was integrated to implement the BB type of a multi-ink color separation algorithm. Additionally, in order to reconstruct the spectra and adaptively map to the corresponding tone values (fractional dot area) for every color in test/training datasets, the MS approach in the reverse process was optimized by iterating the KCR components of BB algorithm in terms of the measure of RMSE (root of mean square error). The predictive performances of 2 models derived were tested for each of subgroup in the IT8.7/4 datasets mentioned above. Two measures of both the mean CIEDE2000 (i.e. E*00) and the mean RMSE were used. The results showed that two types of algorithms, used in the printing process of 7-ink CMYKRGB, were successfully proposed. The mean E*00 values are 1.04 and 0.79 in the forward and the reverse processes respectively for the MS type. Also 0.00098 of the RMSE value was obtained for the reverse transform of the MS type. It implies the spectral reflectance of every color in datasets was satisfactorily reconstructed. Subsequently, following the preliminary study, by taking two matters of “metamerism” and “wide-gamuts” in mind, feasible application modules of Hi-Fi multi-color process toward the spectral/complex color images was derived and proposed. Then, Sets of image-processing algorithms were implemented in the process of scanner-to-monitor, and then monitor-to-printer color transform in the study. Eventually, to cross verify performances of models derived, a set of forced-choice paired comparison psychophysical experiments carried out under a viewing phase of CIE D50 illuminant.

Updating a CMYK Printer Model Using a Sparse Data Set

Two distinct approaches for updating a CMYK printer model in response to systematic changes in print device behavior are presented. In the first method, a corrective model is constructed from a sparse set of newly acquired characterization data and used in addition to the initial printer model. A number of corrective models are investigated, including linear, quadratic, and artificial neural network models. The second method involves directly updating the parameters within the printer model. The updated model parameters are obtained using both the original characterization data and a set of newly acquired data. Both methods are evaluated in a set of experiments in which either the paper stock or the cyan toner cartridge is changed. The corrective model approach is found to be the most effective. The most successful corrective models removed between 76% and 100% of the systematic error.

Digital Offset Printing – Going Beyond 4 Colors

While 4-color CMYK printing is the norm for mainstream offset printing, all HP Indigo digital presses have the option of printing with up to 5, 6 or 7 different colors. These extra color stations can be used to improve image quality by increasing the color gamut, decreasing graininess, reducing illumination sensitivity, or adding special effects to the printed output. The HP IndiChrome Pantone® certified ink mixing system is one key enabler of these improvements, allowing customers to create Pantone® or custom-matched spot colors at their own site.In this paper, we show how the color gamut of a digital press can be increased through the use of additional full-density inks, such as green and violet. We also show how the graininess of a print can be decreased through the use of light inks. In particular, we show how the addition of a gray ink can decrease the illumination sensitivity, improve the gray neutrality, and reduce the graininess of a print. Finally, we highlight some of the special effects that can be created when using specialty inks such as the digital matte ink.

Addressing the Problems of Color Science and Management in Toner-based Digital Print

There are long standing problems in achieving accurate and consistent colors in digital laser printers and color copiers. Despite efforts of incorporating a standardizing ICC profile in digital color equipment, the ICC profile is still subject to various internal and external factors. The inherent conflicts of color management are associated with the calibration of color printers, the differences between the monitor and the actual CMYK prints, soft color proofing on the RGB monitor, inconsistent printer settings over time, variation of colors in different printers and color inconsistencies in repeated printing.This paper aims to address these problems and presents a novel solution for them. The solution was developed based on both objective and subjective color comparison and Artificial Intelligence technology. It is used to calibrate and stabilize digital printers in a quick and easy fashion by means of ICC profiles.

Factor Spaces of Spectra Sets of Color Prints

Dimensions of factor spaces of spectra of color prints in various spectral representations have been investigated using principal component reconstruction and cross validation of color differences between original and reconstructed spectra. Extensive sets of spectra of color prints printed by various graphic arts technologies have been studied. It has been shown that the most reliable reconstruction is achieved using space of logarithms of reflectance factors and empirical ψ–space. The dimensions of primary factor space of these spectral representations depends on actual printing technology and vary from four for CMY and CMYK prints to six for Hexachrome® and spot colors prints.