How Do I Determine the Exposure Time of a Ps Plate?

How Do I Determine the Exposure Time of a Ps Plate?
3 min read
28 October 2022

The PS plate's exposure time is mostly determined by its photosensitive range. Sensitivity and spectrum characteristics of the light source, as well as other factors As a result, if you change the PS version of a different brand or the light source, you must use the measurement and control strip to do a series of tests on the PS version to determine the correct exposure time.

How do I alter the exposure time of the PS version based on the conditions?

  1. There are no dots; instead, the lettering is thicker. The original form of lines and solids can extend exposure time, eliminate minor filthy spots and stains, and shorten cleaning time.
  2. After a long period of storage, the blank part of the negative turns yellow, or after manual imposition, two or three layers of blank film bases are superimposed together, which can slightly increase the exposure time; the original plate with low density in the solid part can reduce the exposure time.
  3. Because the pressure of the proofing machine is lower than that of the printing machine, the increase in the proofing dots is smaller than the increase of the printing dots, thus the exposure time of the proofing plate should be less than the exposure time of the printing plate. In the proofreading version, 0.5% of the outlets are normally eliminated, while 1% of the outlets are retained.

Strictly speaking, when defining the tone reproduction curve for the color separation plate creation of layered drafts, the difference in dot gain under various situations should be considered and compensated. Because the standardization of this procedure in China is not particularly excellent, the exposure period must be adjusted according to the production conditions of the individual printing facilities. If the dot rise rate in our factory's printing process is high, the exposure time might be increased. Depending on the substrate to be printed, the exposure time for printing the printing plate of offset paper should be longer than for printing the printing plate of coated paper.

Why do you need to pump the air when printing and exposing?

Using the manufacturing of the positive pattern PS plate as an example, when printing the plate, if the film surface of the negative film is not in close contact with the photosensitive coating of the PS plate. If there is a gap in the middle, the light will shine obliquely from the edge of the blank area of the negative film onto the image and text. The photosensitive layer right below decomposes the margin of the graphic section, causing the image to blur. The dots become smaller, and the small dots and thin lines vanish.

Because one side of the printing frame is transparent glass and the other is a rubber pad. When the vacuum pump sucks out the air in the printing frame, the air pressure inside is low, and the rubber pad will release the PS plate due to the action of the external atmospheric pressure. The original negatives face the glass and are carefully glued together.

In case you have found a mistake in the text, please send a message to the author by selecting the mistake and pressing Ctrl-Enter.
zheng yimin 2
Joined: 1 year ago
Comments (0)

    No comments yet

You must be logged in to comment.

Sign In / Sign Up