Colour Management for Newspaper Printing

　In the newspaper printing production, usually the layout of advertising topics produced by the advertising company, the layout of news topics produced by the pre-press department of the newspaper, the printing plant to get the digital files of the different pages, after the large version of the spelling, the output plate on the machine after printing. Due to the colour decomposition of the pre-press process and the colour synthesis of the printing process are produced by different companies, and there is a lack of communication between them, which makes the whole production process of colour newspapers often lack of effective colour management, resulting in quality disputes such as off-colour, rubbing dirty and so on. Therefore, how the newspaper printing process for effective colour management is the focus of every newspaper printing plant should be concerned about.

　　Newspaper printing problems

　　1. Problems in pre-press plate making

　　In the pre-press plate making process, due to the lack of in-depth understanding of the colour management of some pre-press production staff, in the picture mode from RGB to CMYK conversion, often using Photoshop software default coating paper printing characteristics of the file (such as often used Japan Color 2001 Coated.icc, etc.) as a colour separation of the target characteristics of the file. Japan Color 2001 Coated.icc, for example, which represents the colour space and the colour space of newspaper printing is very different. In this case, the colours of the colour-separated images cannot be accurately reproduced in the printing process. An even more obvious disadvantage is that the total amount of ink specified by Japan Color 2001 Coated.icc is as high as 350%, i.e., after the black part of the picture has been colour separated, the sum of the dot-area ratio of the CMYK four-colour ink is close to 350%. This is not only a waste of ink for newspaper printing, but also will lead to printing faults such as scuffing and dirtying of the newspaper when receiving the paper because the ink cannot dry in time.

　　In addition to the use of coating paper printing characteristics of the file as a colour separation of the target characteristics of the file, some pre-press production staff also use newsprint printing characteristics of the file (such as ISOnewspaper26v4.icc, etc.) as a colour separation of the target characteristics of the file. ISOnewspaper26v4.icc, for example, the provisions of the black ink starting value of 0%, the maximum value of 95%, the colour separation option to select the maximum degree of grey component replacement (GCR). In this case for colour separation of the picture, after printing the black ink replacement amount is too much, easy to lead to the middle tone and bright tone parts of the density, gloss decreased, the level of loss is more serious, the colour saturation is poor. At the same time, due to the excessive amount of black ink substitution, black becomes the main colour, while domestic newspaper printers often use square dots when screening pre-press documents, and the dot angles of the CMYK four-colour printing plates are correspondingly set to 15°, 45°, 90° and 75°, of which the black plate is not arranged as the main colour plate in the 45° direction, which results in the coloured parts of the overprinted images made of the four-colour ink, and the colour parts of the overprinted images made of the four-colour ink. Especially in the mid-tone and bright tone parts are prone to tortoise, which in turn makes the picture rough and the level is lost.

　　Therefore, we believe that Photoshop software default printing characteristics of the file and the newsprint printing characteristics of the file, are not suitable for domestic newspaper printing colour separation. Domestic newspaper printers need to print calibration, according to their own process characteristics of the printing characteristics of the file, for pre-press colour separation, proofing and set the colour block colour to use.

　　2. Problems in the printing process

　　In the actual production process of newspaper printing, due to the majority of newspaper printing factories either because there is no densitometer, or because the newspaper is not set on the measurement and control bar, or because the printing workers did not get into the habit of controlling the amount of ink by detecting the density of the ink, the ink control in the printing process mainly relies on the experience accumulated by the printing workers over a long period of time. In addition, because the picture editors and pre-press production staff used to see the colour of the monitor as a measure of the printing effect, always feel that the newspaper after printing the colour is not bright enough. So some newspaper printers in order to meet the requirements of the picture editors and pre-press production staff, intentionally in the newspaper printing process to adjust the amount of ink, so that the actual density of the four basic colours of the CMYK value is significantly more than the international standard of newspaper printing ISO 12647-3 and the national standard GB/T 17934.3 recommended by the four basic colours of the CMYK value of the density of the standard.