Data Management Method for Copying and Restoring Originals in Color Printing (2)

Proofing is one of the most important and difficult to control processes in color platemaking

Proofing is the most important and difficult to control process in color platemaking. The biggest problem with domestic proofing is that many companies do not have a signal strip or a non-reflective densitometer when doing the profiling. Even if there are imported Bruner bars or copied Bruner bars, there are reflection densitometers due to the signals used. The strips were inconsistent with the field density (film density at 100%) of the pieces that were put together for proofing. The information detected on the strips could not faithfully reflect the information on the proofs. For example, the off-the-shelf PS version can be proofed with 8 sets of 16 open films. At the same time, the 8 sets of 16 open films are proofed at the same time. The 8 sets of films are sent from 3 output centers and one output center. The field density of the film is 3.0, the field density of one output center film is 4.0, the density of the film of the other output center is 5.0, and the density of the Bruner signal bar we use for detection is 4.2. After the Brunel signal bar shows that the dots at 3% are neat, 95% of the dots are not glued. After printing, the actual ink density is C:1.55, M:1.4, Y:1.0, K:1.8, but actually 3% of the film on the field with a density of 3.0 on the film must be lost. 95% of the film with a film density of 5.0 on the field must be pasted. Only the film with a density of 4.0 on the field and the Brunel signal Information (such as solid ink density, dot gain, contrast, etc.) is inconsistent with the actual information after the films delivered by the three output centers have been sampled. In fact, the information displayed on the Brunel signal bar at this time does not have any guidance on proofing. The Bruner signal strip and the reflection densitometer are virtually empty.

Shangpin Company adopts the following methods to solve this problem: It requires the customer to scan, film, and proof in the same company. When the film sent from another output center requires proofing, the transmission density meter must be strictly used to check whether the percentage of network points is accurate or not. Is it consistent with the field density of the company's signal strips, otherwise it refuses proofing.

In terms of technology, we designed a set of signal bars for controlling proofing as follows:

Color print copy, color reproduction data management methods:

The biggest advantage of using this signal strip is that the information reflected by the signal strip is exactly the same as the information displayed by the proofing film. Since the signal strip is formed by the image-setter output, it is not purchased or copied. This signal strip output environment and general The environment for the output of computer files is the same. The field density of the signal strips is the same as the field density of the soft films required for proofing. For each type of film, a set of signal strips output from the brand must be used to control the proofing. For example, the signal strip formed by the output of Kodak film can only be used for the proofing of the Kodak film output. The signal strip formed by the Agfa film output can only be used for the film proofing control of the Agfa film output, otherwise the thickness of the film base is inconsistent. The light transmittance is inconsistent, and the information caused by the signal bar does not match the information on the proof film.
The signal strip can measure the proof dot gain rate and density contrast K value according to the reflection density meter to measure the ink color shift, ash and efficiency, detect whether the dot at 3% is neat, and whether the dot at 95% is dead or not. Density and other parameters.

Proof expansion rate = (50% fine dot density value - 50% coarse dot density value) × 100% dot gain rate should be controlled within a reasonable range

Density contrast K value = 100% field density value - 75% dot density value 100% field density value

The larger the K value, the better the amount of ink, and the 75% fewer outlets. The K value is better.

The signal strip and the proofed film were put together and proofed. After the proofing was completed, a magnifying glass was used to check whether the dots at 3% were neat and 95% of the dots were pasted. If the signal strip can be output with the layout software around the film, it would be great.

With this signal bar and reflection densitometer faithfully reflecting the proofing information, the following discusses how to restore the color of the original during the proofing process.

Firstly, the printing ink, paper, and auxiliary equipment used for proofing should be prepared and kept stable, and the temperature, humidity, PS exposure time, color sequence, and other parameters of the proofing room should be stabilized. Through the previous discussion on the three processes of scanning, producing, and filming, the scanning process faithfully restores the dot percentage of the original document to a computer image file without any loss in the dot percentage; the production process does not make any adjustments to the image file, and the dot percentage There will be no loss; due to strict detection and control, the percentage of outlets in the image will be faithfully restored to the film and the percentage of outlets will not be lost; if the outlet expansion rate is limited to a very small (such as 5%) during proofing The percentage of outlets will not be lost. Proofs should be consistent with the originals and the colors of the originals should be faithfully restored. However, due to the different inks and other raw materials used by each company, even if there is no increase or decrease in the percentage of outlets at the time of proofing, there will be a certain gap in the color of printed proofs and originals.

In order to restore the original, we removed the Kodak standard reflection color block that was originally scanned with the gray ladder ruler, opened the scanned file, made a PageMaker file, and sent it as a regular hair piece, together with the proof signal strip. . After repeated experiments, when the visual proof (preferably visual observation by many people) is the same as Kodak standard reflective color patches, record the ink density values ​​of the yellow, blue, solid, and black solid patches, such as the red solid density of 1.4. The blue solid density is 1.50, the yellow solid density is 0.9, and the black solid density is 1.8. These data should vary according to the ink and other raw materials used by each company, and may vary depending on the density of the measurement density meter. . With these data, as long as the percentage of the first 3 process outlets does not increase or decrease, the 4-color field density values ​​will be sufficient just for the red, blue, yellow, and black density values ​​for proofing. achieve.

Tools for testing proofing include: reflection densitometers, self-made proofing signal strips, magnifiers, Kodak standard reflective color patches. The purpose is to align the finished product with the original. A set of red, blue, yellow and black ink spot density values ​​of a restored manuscript was detected so that the dot at 3% was not lost, the dot at 95% was not pasted, the finished sample was not dirty, and the registration was accurate.

The above describes in detail the work that Shangpin Plate Making Co., Ltd. has done in color printing, copying, and restoring originals. Now let's briefly introduce some matters that should be noted when restoring originals in color printing. First of all, the printing ink and paper should be the same as the printing ink and paper used for proofing. Secondly, the same signal bar as the proofing should be used to detect the printing situation when printing the PS plate. The dots at the % are not stuck, the PS plate is not dirty, and the density of the ink can be controlled with a reflection densitometer when printing.

In short, the copying and restoration of manuscripts is a systematic project, and every link must be implemented with data management. Each step must have detection tools to detect, otherwise years of experience can hardly achieve the goal.

Author/(Wang Baizhi)