When printing a job, the dots tend to print larger on the press than on the plate, which makes the output darker than the original file.
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Digital film |
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This is due to different factors:
- the type of ink: the more fluid the ink is, the more it will spread under pressure of the press.
- the type of substrate: paper with a rougher and more porous surface (like uncoated paper) reflects less light, making the printed area look darker.
- the type of press:
- offset presses typically print at a 67% density for a 50% dot,
- flexo presses have an even higher dot gain as they put more pressure on the substrate,
- gravure presses have a dot gain similar to offset presses for small dot sizes (up to about 30%) and a sharply increasing dot gain for higher percentages (70% prints as solid).