The key to printing high-quality images: scanning color separation (a)

Unscheduled technical exchanges with related customers are one of the means to improve the service level of printing companies, increase mutual understanding and friendship, and improve and expand production and management. In the exchanges, many art editors, advertising planners, photographers, and prepress producers are often complained about the poor quality of color pages in books, magazines, and advertising leaflets. It is mainly because faithful reproduction of originals and serious color distortion cannot be achieved. Sometimes there is imbalance in brightness and darkness, the level is reversed, and sometimes the contrast of the image of the proof is too large or the color is too light. How to deal with it, I would like to discuss with the industry peers from the pre-press scan separation.

Prepress production has basically determined the general quality characteristics of the printed product. Only the degree of dot reduction and the depth of ink can be adjusted when printing. To change the color and tone structure of the image and improve the visual effect, we must work hard on the operation of pre-press scan color separation. It is not possible to print high quality images with an imported imagesetter, CTP system, and four color machines. The key to the products is correct understanding and operation.

1 Choosing the right color separation route is the basis

The picture quality provided by the customer is uneven. If there is no high-quality manuscript, it is impossible to make high-quality prints, which is not necessary. In addition, some of the pictures have color distortion or poor accuracy caused by improper scanning and color separation.

● Use low-grade platform scanners to reduce operating costs during prepress production. Many non-professional prepress production staff, especially those of small advertising companies, generally adopt low-cost home-level platform scanners to process images. The scan quality is poor, resulting in illegible pictures, unclear levels, and low saturation levels. The color separation characteristics of these images are that the cyan, red, and yellow versions are lighter, the black version is heavier, and the black version is entirely used to adjust the overall image hierarchy and hue, and the images are inevitably gray. This type of scanner can be used only for general line drawing scans or general small-scale renderings.

● Use originals from home digital cameras. To handle the A4 format color picture, no domestic high-end or professional digital camera with more than 6 million pixels or more, professional optical lens can not meet the pre-press production requirements, the common common home-level digital cameras are Sony F828, Canon Pro1, Nikon D70 And so on, the images taken by these digital cameras tend to be less saturated, difficult to open and the images are too sharp, requiring further adjustments to suit printing requirements.

● Network downloaded images. Due to the limitation of network bandwidth and the inaccuracy of the network image itself, the resolution of images available for transmission and download on the network is often low, which is basically 72 DPI, and the high compression format with lossy image details is mostly. To meet the requirements of professional printing, the resolution must be at least 300 DPI.

● Prepress operators are often unable to master the operation of scanning and color separation. They are limited to relying on computer screen colors for subjective adjustment. Advanced technologies for high-end professional scanners and pre-press systems can not fully utilize image processing capabilities. .

● Prepress operators lack the necessary aesthetic appreciation capabilities and the correct analysis of manuscripts and the appropriateness of the printing requirements. The correct parameters cannot be set and adjusted according to the features of various manuscripts and the printing methods, so that the printed images cannot be achieved. To the desired effect.

(to be continued)