Gray scale ruler exposure strip detection method
In order to ensure the accuracy of the dot transfer, the control bar is usually used in actual production to determine the exposure required during printing. The control strips for printing include continuous gray scale, UGRA test strips, and Japanese FUJI test strips.
Here we are going to introduce the use and detection method of continuous adjustment of the ladder as the exposure control bar, which is the most commonly used in normal production.
Generally, there are two types of gray scales, 15 and 21, and the difference is 0.15. That is, for every additional level, the density increases by 0.15. Indicates that the corresponding exposure will increase by 10%. If we can't find the shaded gray scale, we can temporarily use the gray scale used in paper printing (this ladder factory can be found in any printing plant or non-forest export company) for testing. However, it should be noted that in this case, the dots in the ladder should be reversed (because the gray ladder used for paper printing is positive and the opposite of CD printing). That is to say, after marking 95% of the dots after printing, you need to observe whether the remaining 5% of the dots can still be seen. If they can be seen, it means that 5% of the dots have not been lost. Also mark the 10% dots section to see if the remaining 90% dots can be seen after printing. If they can be seen, we can say that 90% dots are not blurred after printing. It should also be noted that the number of lines of paper offset printing is exactly the same as that of the CD offset printing, so this method can only be used as a reference.
Of course, if conditions permit, you can go to Film Export to request the production of 175-line negative graph continuous gray scale ladders (UGRA test strips, Japanese FUJI test strips generally cost several thousand yuan, and make negative graph continuous gray scale ladders Only need one or twenty yuan). In this way, the shade-type continuous gray scale ladder can be used as the original version (film) when printing, and it is closely attached to the PS version. Determine a fixed light intensity (illuminance), adjust the length of exposure time, and perform trial exposure separately. After developing the PS plate, use a magnifying glass at least 15 times to observe the dot transfer. If 2% -3% of the outlets are not lost, more than 95% of the outlets are not blurred. Prove that the exposure is basically bright. You can record the exposure time and light intensity at this time, and you can print according to this parameter in future production.
The light source of the printing machine will decay after long-term use. This requires that we must constantly detect and adjust the exposure of the printing machine in order to make the dot transfer within a controllable range.
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