The Power of Colour. aniva

Transcription

1 The Power of Colour. aniva

2 Preface aniva enables images to be printed on the basis of image data within the colour gamut of photographic prints. Lithography and colour management are adapted in addition to the offset printing inks. This brochure provides an overview of the necessary specifications and procedures. In this context it is vital to understand that all the individual steps in prepress and production are closely interrelated, which necessitates and renders effective standardised procedures based on colour management. Certain topics, such as metrology and make-ready at the workplace in prepress or detailed information on press hall standardisation, have been omitted. Please refer to the extensive technical literature available. The information below will provide you with a better understanding of the entire subject of colour management and inspire you to think up new ways of optimising processes in your own company.

3 Colour perception 3 The eye and the light spectrum The retina of the human eye contains so-called receptors which convert the detected light into nerve impulses. There are two kinds of receptors. The rods are the more lightsensitive but colour-blind receptors. Besides the pure black and white vision they are (among other factors) responsible for spatial vision. The cones are the receptors responsible for colour vision. There are three groups of cones, each of which is particularly sensitive to a certain range of the spectrum. b c a Retina b The incident light is broken into the spectral colours as it passes through a prism. c Visible light (electromagnetic waves from 380 to 780 nm) a (Visible light) The primary colours which we allocate to the cones (according to their sensitivity) are red, green and blue. When referring to the colour vision of our eyes, we speak of additive colours or additive colour mixture. The more intense the light waves, the brighter we perceive our environment or the higher the amount of light reflected by the object, the brighter the object that is hit by the light appears. We perceive the lack of light or a low light reflection as black or dark. The human eye is capable of interpreting optical densities of up to 3.0. We perceive the optical density of 3.0 as absolute black; the optical density 0 as white. All the colour gamuts and contrast ranges we perceive are located within this range. No printing method is capable of reproducing these gamuts and ranges. Today s standard ranges in offset print productions amount to an optical density of about 1.9 in black. Furthermore, the colour mixture taking place in printing is not of the additive but of a subtractive kind. The more printing ink applied, the darker it appears.

4 Colour perception Colour models The primary colours of all printing methods are not red, green and blue (RGB) but cyan, magenta, yellow and black (CMYK) (see above). Black is the fourth colour which increases the printable density range (contrast). The subtractive primary colours of cyan, magenta and yellow cannot achieve the corresponding optical density for black (as we see it), even if all three colours are superimposed. Additive colour mixture - RGB Subtractive colour mixture - CMY (presentation without black) 4 Colour spaces in comparison These three depictions of different colour spaces show the problems related to colour management supported by ICC profiles. Each transfer from a large RGB colour space to a smaller CMYK colour space (for offset printing) bears the risk of socalled separation errors. Each graphic arts company can generate an individual ICC profile, based on individual software settings, by means of a customised standardisation of the press hall. Any compatibility with other producers is therefore rather incidental. The wide range of ICC profiles in use tends to cause confusion. The wrong inhouse profiles might be used for separation purposes or the images of different suppliers might be calculated on the basis of different profiles. In both cases, the printing result will never fulfil expectations. This 3D colour range depiction (1) shows an expanded RGB colour space. The considerably smaller Euroscale CMYK colour space is included in this RGB colour space. This depiction shows clearly how little of the visible colour space can be reproduced in offset printing. The 3D depiction (2) shows two CMYK colour spaces (Euroscale and aniva ). The aniva colour space is larger and, besides the increase in presentable colours, characterised by the enhanced image definition in the shadows. This picture 3D depiction (3) shows two Euroscale CMYK colour spaces in comparison. Their different structure is easily recognisable. It is very likely that the printing presses on which the IT8 charts were printed off had been set up according to different values and specifications. We can also assume that different printing inks were used for proof printing.

5 The aniva system 5 Photography is the only medium which faithfully perceives and reproduces the coloured vision of the human eye. For this reason, the quality of the photograph print is regarded as the world-wide image standard. If, however, high quantities of an image are requested, printing has always been the more efficient method and, above all, is more cost-effective and quicker. The options of image printing are constantly being refined and further developed in order to adapt the printing result to the high quality of the photographic print. The German company Epple Druckfarben AG has now developed aniva, a system which brings the world of printing a decisive step closer to the world of photography. Offset printing, proof, layout and photography are now of comparable quality. A standardised process chain matching the image perception of the human brain provides the viewer with a new vision of coloured and monochrome images. aniva offers designers a new dimension in visualisation of ideas, ranging from the most delicate pastel hues to extremely bright colour shades, from light grey shades to the deepest black. The close match between original and print also considerably simplifies the designers communication with both parties, i.e. with his client and his printing partner. Thanks to aniva, offset printers achieve density ranges on book paper which correspond to the Eurostandard that has up to now only been achieved on art paper. The printing results are more predictable in a standardised process chain and make aniva an appealing and economic product. The complete version of the aniva system consists of aniva ICC profiles, aniva printing ink, printed in aniva densities, and a standardisation according to aniva. Even the use of aniva inks on their own provides a number of advantages. aniva inks meet the requirements of ISO Therefore, the offset printer is able to print existing or new standard print jobs. Thanks to the higher pigmentation, the printing density can be easily enhanced on demand without increasing the risk of offsetting. The higher densities render the image more colourful and richer in contrast. If the proof has not been adapted to the expanded colour space, the print will appear more colourful. Usually the customer s response is positive. In the event of critical jobs, however, this should be pointed out to the customer. Printing in higher densities offers another benefit: Minor fluctuations in the ink feed, which are impossible to avoid in practise, play a far less important role for the aniva densities. The quality remains constantly high throughout the entire print run.

6 6 The image range The quality of the image is determined by the following aspects: Transparency / Eye Photographic paper Offset printing The range of grey-value gradations gives the image a threedimensional character. The grey-value range of the image is determined by the colour black. Today s standard media represent the following ranges: Transparency = log 3.0 density max. in black (the human eye can perceive black up to 3.0). These patches show how the contrast range increases and the white gains in luminosity if the log density increases. At the same time, the three-dimensional impression increases due to the high contrast range. Photo = log 2.4 density max. in black. Offset print = log 1.9 density approx. in black.

7 7 The colour space The observer s mood and feeling are addressed largely by the photogenic colours of images. The following factors, among other things, play a decisive role in shaping the observer s opinion: The distance of 0.5 density units from black to the darkest chromatic colour is perceived as balanced. At lower distances, the prints seem to lack in image definition as the picture details don t stand out sufficiently against the colour. If the distance from black to the darkest chromatic colour is too high, the image seems too dense and the colours loose some of their visual effect. Picture 1 (left page) shows an image of 0.5 optical density distance from black to the darkest chromatic colour. Picture 2 (obove) shows the same image with a higher optical density distance from black to the darkest chromatic colour. The distance between the chromatic colours should amount to log 0.1 density.

8 The aniva system in printing practise The aniva system consists of the aniva Euroscale ink, the aniva ICC profile, and a standardisation according to aniva Euroscale. 8 The aniva Euroscale ink Based on a new binder combination of renewable raw materials, aniva Euroscale inks offer improved dispersability of the pigments and higher colour intensity. As aniva Euroscale inks meet the requirements of ISO , the inking of the process standard offset printing (according to ISO ) is obtained in the standard range of printing densities (B 1.9, C 1.45, M 1.45, Y 1.4). If the printing density is increased to aniva density (B 2.4, C 1.9, M 1.8, and Y 1.7), the colour space is expanded evenly by 20%. The ink feed in the printing process is much more stable than that of traditional printing inks due to the decreased water absorption. The grey scale is defined based on the specifications of the aniva profile. The aniva ink profile The aniva profile is a specially designed ICC profile which offers optimised colour separation for printing. It takes into account the expanded colour space of the aniva Euroscale ink. Printing standardisation The aniva standardisation is effected for solid densities B 2.4, C 1.9, M 1.8 and Y 1.7. The result can be checked by using the aniva test form and a supplied reference print. Thanks to this standardisation, aniva Euroscale inks can also be used for normal process standard offset printing. As a consequence, different print products can be manufactured without changing the ink.

9 Benefits of the aniva systems at a glance The first system world-wide which is based on a systematic analysis of image perception Black is perceived as black Thanks to the higher density range of 0.3, the image information doubles in perception Thanks to the higher contrast in separation with the aniva profile, the images gain in three-dimensional character The colour white is defined in terms of range so that the paper white of aniva is doubled The readability of texts is increased significantly due to the high black density aniva Euroscale inks expand the colour space evenly with an increasing density of up to approx. 20%; this enables printing without any ink change in normal process standard and in aniva standard Contrast and colour tone of the layout no longer grey in the printing process The aniva standardisation allows you to produce prints at different locations with the same high quality; the same applies to repeat jobs and reprints when using the same image data as that of the first edition The aniva system reduces colour fluctuations and thus offers a more even print-run aniva Euroscale inks are based on a new, vegetable binder combination, which offers an exceptionally wide, universal application range. The ink-water balance is excellent and quickly obtained, the stapling behaviour is favourable, and the transfer characteristics in both straight printing and perfecting are highly consistent The aniva process standard can be used across the systems in offset printing as well as in dry offset printing 9

10 Water The following information on dampening water refers to the use of offset printing presses and is of no relevance for dry offset printing. The following information on dampening water for offset printing presses refers to the use of the aniva colour scale. If the ph value is too high (ph value above 5.2), a slight dot enlargement is caused. If the ph values are kept within the specified tolerance range, the print is clean with sharp dots. 10 The ph value of the dampening water should amount to as this ph value generates a slight dot reduction. Any dot enlargement changes the tonal properties during the printing process. At ph values below 4.5, the ink no longer dries. The ink components responsible for the oxidative drying process are impaired (modified) chemically by the insufficient ph value.

11 Example: The following pictures show in what way the tonal properties influence the visual effect of images. Insufficient dot gain makes the left picture appear to lack in image definition and renders it less brilliant. The image message is lost due to an insufficient contrast range. The middle picture with the optimum dot gain shows the best image definition properties and brilliant colours in fine tonal gradations. The right picture seems overloaded due to the excessive dot gain, the depth is too compact and lacks in image definition. 11 Insufficient dot gain Optimum dot gain Excessive dot gain

12 Water 12 The water conductivity provides information on the water s purity. The reference value should be kept between 1,200 µs and 1,600 µs. These values ensure good transfer properties of the printing inks and prevent the rollers from furring. If the conductivity is too high, there is a risk of the rollers furring up. Lime scale is one of the most frequent causes of an excessive reference value. If the conductivity is too low, the inks transfer properties change and the printing process is no longer controllable. Degree of water hardness: The water hardness ( dh) indicates the salt content (calcium and magnesium compounds) in the water. The scale ranges from 0 (very soft) to approx. 30 (very hard). It has transpired that 8-10 dh is the most suitable range for offset printing. If the water is too hard, (scale) deposits form on the blankets and rollers. This nonsoluble scale deposit causes the roller surface to become more hydrophilic (water-friendly): The ink is rejected and the rollers run dry. Water temperature: The temperature range of C has proven to be ideal. Inking unit temperature control: C. The temperature of the inking units must be controlled to ensure constant application conditions at all times. If the temperature is too high, the ink becomes thinner and the ink transfer is no longer consistent. Moreover, this can lead to an excessive dot increase. Another problem caused by too high water temperatures is the excessive evaporation of the alcohol. If the water temperature is too low, the resulting impact on the ink viscosity also leads to an inconsistent ink transfer. Air humidity in the press hall The air humidity should amount to approx %, 60% maximum. Otherwise the paper becomes too damp or water may condense on the ink in the ink fountain. These effects can lead to uncontrolled emulsification of the ink or to modified ink trapping on the paper. These effects are not controllable and can cause strong visual changes to the print image. In the worst-case scenario, the ink is changed to such an extent that sufficient drying or rub resistance can no longer be obtained. Alcohol in the dampening water 7% alcohol for aniva system 5-6% for aniva system with alcohol-reduced rollers The printing ink s impact of the cylinder s rolling behaviour is largely dependent on the water consistency. The alcohol has a decisive impact on the water consistency and thus the rolling properties of the cylinder. This is why these values must be monitored and adhered to in order to ensure a stable printing process. Blanket If the blanket is too soft, excessive dot gain, dot enlargement, slur or doubling may occur. If the blanket is too hard, the dot edge is too smooth. Should blankets of other manufacturers or blankets with different properties be used after the standardisation of the offset printing process, the standardisation procedure must be repeated, using these new blankets as a basis.

13 Notes on printing when using the aniva system Colour sequence The correct colour sequence for the aniva printing system is black-cyan-magenta-yellow. It should never be changed. Proof In general, it is a fact that proof systems, no matter what printing procedures they are designed for, are incapable of 100% simulation of the expected print result. As with other printing inks, the proof procedure used must be adapted to the printing conditions by means of ICC profiles (colour management process). These can be easily adapted to the aniva system using the corresponding profiles, as the inks used in inkjet printers or tonerbased systems (latest toner generation) have a very large colour space. In principle, each known proof system comprising a larger colour space than the aniva colour space is suitable for the visualisation of the final result. A respective metrology must be applied to adapt these devices. Contact: Epple Druckfarben AG Gutenbergstraße 5 D Neusäß/Augsburg Fon +49 (0)821/ Fax +49 (0)821/ info@aniva.info Medigraph GmbH Marienhof Marienstraße D Hückelhoven Hilfarth Fon +49 (0)2433/ Fax +49 (0)2433/ info@medigraph.de Drying No special requirements must be fulfilled during the drying process of the sheets. The ink stands out due to its good absorption characteristics and stapling behaviour. Infrared drying is not recommended for strongly oxidative drying inks. Should problems occur during the drying process, the press parameters (water values, additives) must be checked. Finishing The properties of the aniva Euroscale inks are identical to those of traditional offset inks in the finishing procedures subsequent to the printing process. Paper The aniva method is suitable for achieving good results on all standard papers. The CTP curve should be adapted for coated and for uncoated paper. Printed with aniva Board and Unibrilliant by Epple Druckfarben AG on 150g Klippan Art gloss by CLASSEN PAPIER 13

14 Die Kraft der Farbe. The Power of Colour. La Force des Couleurs. Forza ai Colori. La Fuerza del Color. De Kracht die Kleur uitstraalt. aniva

15 Epple Druckfarben AG Gutenbergstraße 5 D Neusäß/Augsburg Fon +49 (0)821/ Fax +49 (0)821/ info@epple-druckfarben.de