Choose the right digital proofing system
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With the development of computer-to-plate (CTP) in recent years, the industry generally believes that this technology is bound to replace the existing film process, but its development has received some obstacles. Because the filmmaking process using the film can still provide a certain flexibility for manual modification, such as typo or partial plate change. The direct plate making is a cloth-like image directly on the plate using the plate-making machine. All the imaged data can not be lost, otherwise the full-page layout needs to be re-exported. That is to say, Ctfilm, a computer-based direct plate making (CtPlate), is more rigorously a set of reliable digital workflows to properly handle the production process from the designer to the press. Therefore, the most controversial issue is not whether lasers can be used to create high-precision dots directly on the board, but whether there is an approved digital workflow to replace the existing production methods, and the entire process needs to be considered. Including: digital proofing, computer layout, flexibility in production efficiency modification, cost, trapping and self-filming.
The following is an introduction to the requirements and techniques of digital proofing.
Comparison of digital proofing and traditional proofing
Whenever the effect of digital proofing is mentioned, the general lecture will use the traditional proofing as the benchmark for comparison. Although this comparison is logical, it is often easy to miss the benefits brought by some functions attached to digital proofing. Below I have three broad scopes, including quality, cost and effectiveness, and try to objectively compare the differences between the two.
Quality effect
Color Simulation Capability - Since the traditional proofer is also imaged using ink, the theoretical color gamut it can express is very close to printing. In terms of digital proofing, some equipments can also use the color inks that approximate the ink composition, and the color gamut performance is also very similar to printing. However, the cost of inks and machines is very high (generally between 500,000 and 1.5 million units, depending on the format and accuracy). Other common color printers, such as inkjet or sublimation, can express a wider color gamut than printing inks at a lower cost. The key is how to use the overly rich color gamut to simulate the color gamut of the printing ink, depending on which manufacturer's color management technology is chosen.
Dot Simulation Capabilities - This is an absolute advantage in traditional proofing. Because they use the same set of film printing and printing. For digital proofing to simulate online flowers, on the one hand, it has to pay more than one million yuan to purchase high-precision equipment, but the effect is not consistent with the real printing effect. For example, the accuracy of the digital proofing machine is 2000/3000dpi, and the accuracy of the photo-aligning machine is 2400/3600dpi. The net flowers made by the two are completely different. Most of the devices on the market that can simulate cyber flowers can only meet the visual requirements of customers.
Stability - Because the traditional proofing machine uses the ink of the person and adjusts the pressure, the effect is very unstable. The insiders have this experience: this is the same set of film to take out the proof, the effect is usually different. Digital printing is automated imaging, it can be very stable, and such equipment is not difficult to find.
Reliability - Traditional proofing uses a film that is consistent with printing and is highly reliable. The digital proofing system is designed according to the needs of the prepress process, we divide it into:
1. Design proofing required by individual users who are concerned with cost and design performance;
2. If the output center focuses on production efficiency, the RIP pre-prototype process is widely used;
3. If you pay attention to the requirements of data reliability, it is recommended by the industry after the RIP proofing process.
In addition to the human factors in the entire process, the most likely difference in operation is the RIP calculation. The three methods mentioned above are available on the market.
Cost-effectiveness:
Investment costs – In this respect, traditional proofing is inferior to digital proofing. Because the same production capacity, such as the completion of two sets of four-color proofing in one hour, the investment of traditional equipment requires four groups of machines, supporting printing, printing equipment, plus the required staff and A large factory building. The investment in digital proofing depends on the quality requirements, while the extra labor is close to zero. In terms of material cost, the cost of traditional proofing paper and ink is very low, and the cost and the higher proportion are the plate and the potion. For digital proofing, a split format depends on the individual printer. In general, the rate of return on digital proofing (to a certain degree of quality recognition) can be much higher than traditional proofing.
Performance:
Production speed - on the surface is digital proofing imaging faster. Printers that are common in the market can complete a face of the same quality in 20 minutes. The traditional proofing, regardless of size, does not include imposition, printing and printing time, single proofing action, usually takes 30-40 minutes, but this is only a comparison of the production of a proof. When it is necessary to produce more than one color proof, the speed of the two is relatively close.
A variety of analog capabilities - most of the digital proofers mentioned above can express a wider color gamut than printing inks. Rich color gamut and good color management software make digital proofing not only simulate the effect of printed matter, but also simulate other production effects, such as screen printing, digital printing, inkjet posters, etc., and even simulate The performance under the high-speed rotary press can better meet the increasingly diversified output requirements in the market. The most common example is a set of advertising designs that need to be advertised through different media.
A variety of format capabilities - a complete digital proofing system, in addition to simulating the color effect of an output medium, can also automatically adjust the color of the image in the file for different output needs, the operator does not need to manually modify, Can truly automate the workflow. The characteristics of the above two digital proofs are lacking in traditional proofing.
Digital proofing options
Digital proofing can basically be divided into three categories:
1, design proofing, for color layout design.
2, color proofing, for color effects.
3, dot proofing, at the same time for color and net flower effect.
Overall, Color proof color proofing is the most comprehensive and selective, and the best cost-effective.
In fact, there are many types of color printers that can be selected on the market. The main imaging technologies include laser printing, thermal wax transfer, sublimation, and inkjet. The inkjet type can be said to be the mainstream middle and high-end products.
Introduction to digital proofing hardware:
Thermal Transfer and Sublimation Technology: Thermal transfer technology transfers wax blocks containing pigments to specialty paper. However, the color space that this technology can cover is different from the color space of traditional offset printing. Samples using thermal transfer technology have a rough appearance, and the resulting dots are inconsistent with printed halftone dots; the sublimation technology proofing system uses a printhead containing thousands of heating elements and a color ribbon containing CMYK pigment for proofing . The printhead can produce 256 levels of different heat, allowing the solid pigment to sublimate into steam and condense on the receiving medium. In the central part of each point, the color is darker and the edge part is lighter. When the four printing colors are printed, the four colors are combined to form a continuous tone image; such equipment is expensive to use. The cost is high.
Professional inkjet technology: The inkjet proofing system ejects ink onto paper to form an image. As the level of hardware continues to increase, performance is fully capable of meeting the needs of proofing. Equipment investment costs are also accepted by more and more users, but in terms of the cost of use, it is feasible to provide full service to control costs by professional system service providers due to the need to use special paper and necessary color maintenance work. This practice is recommended by users in many countries.
Laser technology: This technology is highly accurate and produces halftone dots, and the specific techniques used vary. The general color expression is smaller than the printing color gamut, the system precision can vary from 1800dpi to 4800dpi, and the equipment cost is different. Because ordinary printing paper can be used, it is often preferred by users as a color printing device.
The right printer only provides hardware features, and the more important part of the proofing system is the part of the color management software. In the topic of digital proofing, a term called "ICC PROFILE" is often used. This is actually a data file with a standard format, which is used to record the unique color gamut of different color output devices. Applying this "ICC PROFILE" in a digital proofing system is just a common procedure. What users need to know is how effectively this data is generated. Do you allow users to have regular maintenance? It all depends on the technical level of the service provider's color management.
Software introduction
Our perception of the color of nature is determined by the following factors: how the object changes the reflected or transmitted light, and the sensitivity of our eyes to the changed light. The eye is one of the most important sensory organs, and the principle of eye color matching is consistent with the color mixing principle of color light. When red, green, and blue light in the external light respectively stimulate the corresponding cone-shaped cells, the nerves generate electrical impulses, form nerve excitation, and transmit to the visual center on the cerebral cortex, which constitutes a certain color, and different colors will be Different visual effects. The same color will have different auditorium effects under different contrast changes, because the color contrast in the same picture will affect the brain's judgment of color. This is one of the important principles used in our color conversion.
First, there needs to be a way to measure and define color.
Visible colors can be composed of: hue, saturation, and brightness. The hue is the intensity of one or two colors of light that is the largest in RGB trichromatic light. When the RGB quantities are equal, the color becomes unsaturated, it looks gray or white, and the brightness is the RGB light wave that stimulates the eye to perceive the intensity or wave height of the cells. These characteristics can be stacked by a number of "discs" to form a three-dimensional color model. The change in the circular motion of the disc is that the hue shifts from bottom to top to increase the brightness. Each disc moves outward from the center to increase saturation. This model is - irregular, because the eye is sensitive to a color.
Each device has its own gamut space, some of which can be seen on the screen but not by the output device. This is due to the inconsistency of the common space of the screen and the output device. Agfa CMS can connect and match two common areas to solve the problem of color conversion. When using the screen color to simulate the printing color, a method can reduce the gamut space that cannot be expressed to the expressable gamut space, change the color of the whole surrounding environment, and use the relationship between the eyes and the brain to simulate different color gamuts. The effect of the latter, so the latter has a superior method, which enables all color output devices to have a certain color simulation capability.
Digital proofing application
The existing digital proofing technology has been able to satisfy most general users. They mainly pursue speed, stability and cost effectiveness. The performance of these three aspects of digital proofing is significantly better than the traditional proofing. User examples include general books, magazines, and textbooks.
For high-end users, the above three advantages can not fully satisfy them, and color quality is the most important requirement. But because of the strict requirements of these users, a layout often requires multiple modifications during the production process, and many of these types of users, such as advertising agencies, have begun to use digital proofing as a test. Digital proofing has been used in the modification process, and the traditional proofing is done after the modification is completed. This alone can save a lot of cost for repeated proofing.
The above introduction hopes to provide some reference for everyone. Finally, it is proposed that today's digital proofing technology has reached a certain practicality, but users must pay attention to the software, hardware and service capabilities when selecting equipment to achieve the best results.