Analysis of the three types of pre-press proofing and their respective advantages and disadvantages
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The proofs are the basis for the quality control of printed matter and the tools for communication with customers. Their functions are mainly reflected in the following two aspects.
First, proofs can help users check the various information contained in a document for timely modification, such as fonts, images, colors, and page settings. Color is the most difficult to control in proofing, as different substrates, inks, and dot gain rates can cause variations in the color of the proof.
Second, the proofs can be used as a contract between the customer and the printing house. The same sheet should accurately provide the same color as the final print, and the same sheet should be shot out shortly before printing to avoid fading and distortion of the sample due to long time.
Proofing is the process of connecting prepress between production and printing, allowing the user to anticipate the final print effect before printing. At present, the proofing methods commonly used in the gravure printing industry mainly include soft proofing, traditional proofing and digital proofing.
1. Soft proofing
Soft proofing is implemented on a color display and is undoubtedly the most convenient, fastest, and cheapest way to proof. Color displays are required to be accurate and must be properly calibrated. The obvious shortcoming of the soft proofing method is that the resolution is low, only 72 dpi; the accuracy of the color depends on the performance and calibration of the display; it cannot provide a hard copy for reference in the subsequent printing process.
2. Traditional proofing
There are two kinds of commonly used traditional gravure proofing methods. One is gravure proofing, and the obtained proofs are accurate in color and high in reference. However, this proofing method requires grinding, electro-engraving, electroplating and other processes to correct the processing of the plate cylinder. The requirements are high, the electroplating cost is high, and the process is complicated. Therefore, the production cost of this proofing method is high and the cycle is relatively long, at least one day.
Another method is offset proofing, which requires output of film and print, and then proofing on an offset proofer. Although this method can reduce part of the production cost, due to the difference between the offset printing and the gravure printing process, the proofing effect is quite different, such as insufficient density in the field and equal color levels. The advantages of traditional proofing mainly include the following points.
(1) The production process of proofing and printing plates is relatively close.
(2) Proofing and printing use the same rasterized data, and proofing can reveal potential problems such as moiré, layout and fonts.
(3) Good performance for trapping and ink opacity in proofing of spot colors and metallic colors.
The shortcomings of traditional proofing mainly include the following points.
(1) High technical content requires professional technicians to obtain accurate proofs and labor intensity.
(2) A higher investment is required.
(3) There are many processes involved, the cost is high, and the processing cycle is long.
3. Digital proofing
The digital proofing technology is completely digitally controlled, changing the complex printing process in the past while reducing costs. Moreover, the stability of plate making and printing quality is greatly improved. In the process of gravure printing, which does not require the use of film, digital proofing is a more suitable proofing method.
The digital proofing technology is very mature and fully meets the needs of gravure printing. The design elements in the gravure plate are mostly graphics, images, and more use of the spot color, which is mainly because the color of the spot color is more uniform and more beautiful than the multi-color overprint, and has good stability. The use of spot colors in the reverse white graphics or text section can reduce the difficulty of registration. Therefore, to evaluate the pros and cons of gravure digital proofing, it is critical to verify that the proofing system is accurate for the reduction of spot colors. In addition to the general four-color proofing, the digital proofing technology is more and more perfect for spot color. For example, the professional digital proofing system can be used for overprinting and trapping of spot colors, control of spot color transparency, and specialization. Problems often encountered in gravure processes such as color gradation transitions provide a good solution.
The advantages of digital proofing mainly include the following:
(1) Without the need to output film or make a plate cylinder, the production cycle can be shortened while reducing costs.
(2) Samples made based on inkjet technology are generally more stable in quality.
(3) Digital proofing is an important part of digital printing, and its unique stability can provide a standard for the entire printing process, providing a strong guarantee for the improvement of printing quality.
The main disadvantages of digital proofing are as follows:
(1) Some digital proofing systems do not ensure the integrity of document data.
(2) A digital proofing system with a function of processing the net tone requires a high cost.
(3) Spot colors and metallic colors cannot be accurately reproduced, and a specific system must be used.
Undoubtedly, with the continuous development and improvement of color management technology, digital proofing will show greater advantages and dominate in the printing process.