Application of color mark (3)

What data should be obtained when measuring the color scale?
Various printing markets, including publishing, cold-fixed advertising, newspaper printing, commercial printing, etc., have specific demand for density values ​​and outlet expansion values. Although the actual values ​​will vary with each production process, the survey conducted by the GCA Print Properties Committee in 1991 showed that the target values ​​listed in the following table have a The meaning of sex.

Element 100% (field) Print contrast 50% Dot 25% expanded Dots expanded Green 1.25 30% or higher 24% 20%
Product 1.30 30% or more 24% 20%
Yellow 0.98 25% or higher 22% 16%
Black 1.65 33% or higher 28% 24%
Note: The values ​​in the above table are all industry averages and will vary depending on factors such as paper, ink, printer, press operator, plate type, etc. Also note that these values ​​are very effective for copying high quality prints, but do not necessarily disregard the appearance of the images rather than achieving these absolute data.

Is it better to measure the color scale at the time of printing or the color scale at the time of proofing?
In fact, both sensible printing operators or color separation personnel do it. Many people in the industry should know that "no one buys numbers. They buy beautiful images." In the long run, they are right. Proofs or prints with specified density values ​​or dot gain values ​​may not achieve the desired appearance, in which case experienced color separation personnel or printing operators—with the support of a knowledgeable printing customer—will make the necessary The adjustments to obtain the desired image appearance. However, these color separation personnel, printing staff, and printing customers will use color scale measurements to record the process adjustments that need to be made to achieve the desired image reproduction. Also note that the defined dot gain values, such as those provided in SWOP (Square Offset Parameter Description), SNAP (Sensor Offset Parameter Description), and other documents, usually provide the best starting point for image duplication. After reaching these target points, the print operator evaluates the image effect, and then adjusts the ink key appropriately to change the appearance of the copy, ultimately meeting the customer's needs.

Should the color mark be pasted on the back of the model or pre- proof?
No. The original color-coded film should be imaged at the same time as the image being proofed and placed alongside the proofing page or ad. In addition, in the model, the color mark should also be placed parallel to the cylinder of the printing press and run through the full length of the image to be proofed so as to provide effective information.

Can I copy or copy color film?
No. Surveys conducted by the CGA Prepress Committee have shown that in most prepress operations, the use of color copies of copies and copies does not effectively control the process. This is because the color value of the copied or copied color code film has undergone a certain change, which affects the practicability of the color code as an information transmission tool during the copying process. Even if you set the copy conditions very carefully, the chromaticity value may change by 1% to 2%, which means that 50% of the chromaticity value on the original color gradation will become 48% or 52% on the copy. The chroma value. Visual perception factors such as dot gain measurements and gray balance often rely on the surveyor’s knowledge of the correct color film value. If these values ​​change due to factors such as copying or copying, the measurement results will not truly reflect changes in the process and prevent accurate communication of process information.
There are three controversies about copying and copying the original color film:
1, the cost of color film is very expensive, and a unit may need more than one set of film, thus causing a certain burden on the enterprise. However, with the result of measuring with incorrect color scale film, controlling the process often results in error transfer, shutdown, and waste of information. In contrast, purchasing multiple sets of original film to meet the printing company's needs is costly. The cost is still very small.
2. Time progress Sometimes the urgent need for color-coded films and the lack of access to channels are also one of the reasons for copying or copying films. The solution is to plan ahead, or keep enough spare set film on hand.
3. Self-confidence Some institutional groups are full of confidence that their pre-press departments can accurately copy or copy the color-coded films from outlets to outlets. According to this view, the ability of an operator to copy or copy a color separation film under certain control can be applied to a color-coded film to obtain better results. However, the facts show that this view is incorrect in many cases. Precise measurements are required to determine the extent of the changes that result from copying or copying.
The following are four additional reasons why it is not wise to confirm copying or copying a color film:
(1) Any copying or copying of a color-coded film brings about unnecessary changes to the measurement process, although the extent of this change may be small.
(2) The color film is more sensitive than the color separation film for small changes brought about by the copy or copy process. In fact, the print copy process tolerates changes in the color copy film copy or copy change to a greater extent than changes in the color film print copy or copy. Many investigations and studies have shown that in the balance between ink and dot gain, color separations can be more full (or heavier) or finer (or more light), still meeting customer expectations Subjective requirements for copying. In contrast, color-coded films should be measured objectively and must be produced within tight tolerances.
(3) Copies or copies of color patches can give operators and managers erroneous information and can be misleading to operators.
(4) Enterprises have lost the tools to use accurate process data information exchange for control. Unless all color patches are manufactured by the factory, operators, managers, quality control personnel, and customers cannot accurately know which color film is used. Therefore, the actual conditions of the printing process are likely to be confused by the measurement results, resulting in undesirable process changes. In the worst case, the results of all objective measurements need to be used as reliable and non-essential data for stable and high-quality printing. Removed. Duplicating copies of a color-coded film multiple times can only exacerbate the unreliability of the color scale as a measurement tool.

How do you know if a color patch has been copied or copied?
There are two ways. The first method, using a magnifier, checks each of the fine lines contained in the color scale or GATF Star Target element to see if they are degraded by degradation (for example, the thinning or thickening of microline, highlight, or dark tone points, or These elements completely disappear or become blocked). The second method, using a transmission densitometer, measures the colorimetric values ​​of the color patches in the printing primaries, and tests whether these patches are different from their values.