Moiré
The Moiré effect or, in other words, a halftone overlay, is a common phenomenon when viewing prints. It occurs when two even patterns overlap unevenly.
Lexicon
Monitor calibration
In order to judge colours, the computer monitor must be calibrated. This ensures that colours and contrasts are displayed correctly on the screen.
A measuring device is recommended for this purpose, as monitor calibration with the eye is very error-prone.
The resulting calibration is stored as a monitor profile.