First thing is to define at what it means for a printing house to print under the standard. Concept “qualitative print” includes repeatedly reproduced, stable in time print without defects with compliance to some parameters. Every printing house should consider all these components. Get rid of print defects completely is very difficult. Besides, there is a question what to consider for defect. In polygraph for many years the whole list of print parameters and possible deviations from them was generated. Curious, but these deviations are not stipulated in the ISO standard. Naturally, it does not mean, that it is possible to print somehow if only colours of the base would have certain characteristics which might meet the general output. Simply in the standard it means that there is no place for deviations. Nevertheless for its introduction in practice it is necessary to understand, that deviations during printing process can appear, at what degree they influence quality of polygraph edition, how much they are admissible and whether it is possible to reveal and somehow measure these deviations is another question. For this purpose to a subject image of a print the gamut which allows detecting those or other problems at press is always added. Gamut may appear in different ways, they are developed by special institutions, enterprises and manufacturers. But in any case it is not very important as to which gamut is in use, the main thing is to learn all deviations and defects.
It is supposed that on all colourful printed images of one side of a leaf, colours should be combined precisely. But it might not happen. Qualitative colour registration depends on a condition of equipment which in process of its function can show fails of accuracy, a paper used since thinner paper is easier deformed during print process, and put precisely the fourth paint on the first paint layer becomes impossible, a format of the printed equipment (the leaf of a greater format is subject to deeper deformed during print) and from set of other factors indirectly connected with print process, for example, from quality or their tension at installation in the printed car, all of this should be taken into consideration. The indispensability to track such quantity of nuances does not allow to get rid completely from defects.
Perhaps, the situation when the same colour in circulation slightly changes from a print to a print is familiar to you. This phenomenon is sometimes called “difference in hue”. The reasons for its occurrences are quite clear, the printed car as any dynamic system, is difficultly kept in a stable condition. Only if it is adjusted and managed properly at the competent approach it is possible to print long circulations without those differences. Frequently happens that the printer has been adjusted according to the certain requirements, and commenced circulation, but during the process supply of paint has a little decreased or, to the contrary, has increased. A pattern taken out for control has certain traces of paint additions. As a result the personnel might change the amount of paint which then, again, might affect the right printed output. The process of printing is quite interesting and peculiar mechanism, and there is no doubts that no matter how many of obstacles might be, true experts will always overcome them all and prepare a full list of specifications which will guarantee good printed results.
|