The 14th INTERNATIONAL DAAAM SYMPOSIUM “Intelligent Manufacturing & Automation: Focus on Reconstruction and Development”, 22-25th October 2003


Mahovic, S.; Mandic, L.; Agic, D. & Gojo, M.

Abstract: Modernization of the graphic production caused the appearance of different input and output units in the systems of graphic reproduction. Each of them has the same goal to obtain the reproduction true to original reproduction. Different proofing systems are used today for quality control and they play important role in communication between the client and the printer. They are used mostly as a kind of “contract” by which the ordering party accepts and permits the printing of products. From these reasons color management in each particular system as well as its standardizing is necessary.
Key words: ink jet proof, analogue proofing system, CTP system,
print quality, colour management.


Contemporary input and output devices for graphic reproduction of an image comprise the computer with the adequate program support as the input unit. Color printers, digital and conventional printing machines are used as the output units. During the image information transfer onto the corresponding output, changes in color reproduction are possible, because of different working principle of the device (Agic et al., 1999). Before the long run reproduction, as well as shorter ones with great quality demands, proofs are produced. They enable the control of colour and text reproduction and eventual error corrections before the printing process. In dependence on the proofing device impressions are obtained with determined deviations in colorimetric characteristics of inks, from the original and offset printing (Mandic et al., 2001).
This paper tries to determine which proofing device gives reproductions true to offset prints. The device, giving better reproductions, could be used for more secure impression control and as the evidence of the correct reproduction. Computer generated original is reproduced on different proofing devices and in the offset technique with Computer to Plate (CTP) system for printing form production. Densitometric and spectrophotometric measurements determine the deviation of the proofs from the realized reproduction in offset and try to estimate which of the systems is more adequate and more appropriate for the realization of the defined demands in the reproduction quality.
The proofing device based on ink jet technology and analogue proofing device are used in investigation. The proofing devices based on ink jet technology enable direct production of proofs from the computer. Ink jet devices enable the ink transfer onto the paper by means of nozzles. The system ‘drop on demand’ defines the ink droplet by means of the so-called piezo printing heads. The output information deforms the piezo ceramics, which squeezes the ink from the printing heads. The nozzles are very thin and closely concentrated. The ink dries very quickly on the paper so there are no essential changes on the reproductions. Analogue proofing device enables the obtaining colour reproduction of continuous tone by screening simulation. The film separations (CMYK) are used foils with photosensitive diazo pigments and impressions are produced on the polyethylene substrate. Copying through the film (each film separation separately), the disintegration of the exposed parts of the diazo layers appear. Non exposed parts stay on the substrate and the exposed parts are physically removed together with the foil. The obtained proofs are compared with the reproduction in offset. Printing forms for offset are produced directly from the computer by CTP system for plate production. The used systems are optimally adjusted according to the manufacturer specification.
The measuring results are presented in the diagrams with the reference and measured values for surface coverage in the systems CIE*a*b* for colour gamut (Wyszecki, Stiles 1982) and L*Cab* system for lightness and chroma determination (Hunt, 1991). The proofing system, which is better for the colour control of the original, is determined from the obtained values. The proof is determined, which will ensure the ordered that the colours from the proof will be reproduced in offset. Visual comparison of the samples is also done.


The original contains the wedge with the patches of 10, 20, 30, 40, 50, 60, 70, 80, 90, 100% coverage for 155 l/inch. The proofs were made in ink jet technology on Epson Stylus Pro 5000 (proof A). Analogue proof device Agfa Printon CDL 1020 R (proof B) was also used. The same original was reproduced in offset.
Viptronic 2000 (D65/10o) densitometer was used for measuring surface coverage on wedge patches in cyan, magenta yellow and black. These relations are presented in fig. 1, 2, 3, 4.

Fig. 1. Dependence of the measured and reference values.

Fig. 2. Dependence of the measured and reference values.

By spectrophotometric measurements on the instrument Datacolor CS3 (D65/10o) and by transformation equations the values L*a*b*, for the presentation in CIEL*a*b* colour space were obtained (fig. 5). In L*Cab* system the differences in lightness and chroma of samples were presented (fig. 6).

Fig. 3. Dependence of the measured and reference values.

Fig. 4.
Dependence of the measured and reference values.

Fig. 5. Colour gamut in CIEL*a*b*diagram.


Greater deviation of the proofing device on ink jet technology principle is visible in figures 1, 2, 3, 4 (proof A). The deviation is visible mostly on middle tone values on all the colours. The deviations from the reproduction in offset, on analogue proofing device (proof B) are very small. The greatest dot gain on offset prints is between 50% and 60% surface coverage. This is the consequence of the mechanical and optical changes of the screen elements on the printing substrate (Nilsson et al., 1997).
From CIEL*a*b* colour space it is visible that the proof based on ink jet technology has considerably smaller colour gamut which can be presented and it deviates essentially from the reproduction in offset. Colour gamut is decreased in red, yellow and green area. Because of that prints obtained by ink jet, do not give satisfactory data about the colour control. In diagram L*Cab* it is visible that Agfa proof (proof B) has greater lightness on the places C, M, Y than Epson (proof A) and offset one. On the places Y the deviation in tone is visible as well as in CIEL*a*b* colour space.

Fig. 6. Relation of lightness and chroma in L*Cab* diagram.

It is visible from the obtained results that the analogue proofing device (proof B) gives reproduction more alike the ones from offset (smaller deviations). This is the consequence of working principle of the device, which uses the colour separations of the original on films to produce proofs.


The control of colour and text is necessary before the beginning of long run. The proofing devices enable prevention of great waste quantities and unnecessary costs of wrong reproduction. Changes in lightness and chroma among the proofs and offset prints are visible. Ink jet proofs give somewhat weaker reproduction in relation to the analogue ones. This is the consequence of different ink application on the substrate, which does not exclude today’s broad usage of these devices for reproduction control. Changes in dark tones are visible by visual evaluation on both proofing devices in relation to the offset. The prints have decreased contrasts and weaker reproduction of the details especially on the dark tones on ink jet printer.
In this closed graphic system, ink jet proofing system is used for imposition control of graphic layout and analog proofing system for image quality control. By involving CTP system in reproduction, there is no request for further usage of films. That is the reason why ink jet proofing system must take over the control of image reproduction also. This is possible only by using colour management system with weekly calibration of colour devices.


Agic, D.; Mandic, L. & Gojo, M. (1999). Influence of Some
Parameters on the Change of Printing Elements Dimension, Proceedings of 10th International Daaam Symposium, Katalinic, B., pp. 5-6, ISBN 3-901509-10-0, Vienna, October 1999, DAAAM International Vienna, Austria
Hunt R. W. G. (1991). Measuring Colour, Ellis Horwood Limited, ISBN 0-13-567686-X, England
Mandic L.; Agic D. & Ziljak V. (2001). Differences in Colour Reproduction in Closed Systems and through Colour Management Calibrated Device, Proceedings of IARIGAI, ISBN 0-88362-401-X, Montreal, September 2001, Canada
Nilsson, C.M.; Malmqvist, L.; Busk, H. & Kristiansson, P.
(1997). Optical Enhancement of Closely Positioned Screen Dots, Proceedings of TAGA, Taga office, pp. 11-21, ISBN 14623-5604, Rochester, NY, 1997, USA
Wyszecki G., Stiles W.S. (1982). Color Science: Concepts and Methods, Quantitative Data and Formulae-2nd Edition, John Wiley & Sons, ISBN 0-471-02106-7, Canada