As an alternative to dot gain the relative print contrast Krel.(%) is often determined, particularly to check the screen in the three-quarter tone.

A print should have a contrast as high as possible. This means that the solids should have a high ink density, but the screen should still print open (optimum halftone value difference). When the inking is increased and the ink density of the dots rises, the contrast is increased.

However, the increase in ink feed is only practicable up to a certain
limit. Above that limit the dots tend to exhibit gain and, especially in three-quarter tone, to fill in. This reduces the portion of paper white, and the contrast decreases again.

If there is no measuring device available with a direct contrast display, the relative print contrast can be calculated or determined on the basis of the FOGRA PMS.

If the contrast value deteriorates during a production run in spite of constant ink value in solid DV, this may be a sign that the blankets need washing.

If the solid density is correct, the contrast value can be used to assess various factors which influence the print result such as rolling and printing pressure, blankets and underlays, dampening, printing inks and additives.

Since the contrast value, unlike the dot gain, depends to a large extent on the solid density it is not suitable as a variable for standardisation. This is why in the recent past its importance has decreased significantly.

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