Beta Ultra Dottie II, Руководство по эксплуатации

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Hold the Ultra Dottie II parallel to the edge of the plate to get a correct
value of the screen angle in degrees.
Important: The screen angle is not shown for FM screening and for middle tones,
especially for chain dots in AM screening. In a regular screen, the screen angle
will always be shown if the dot area has closed dots (highlights and shadows).
3.5.7.5 Visual Coverage
The visual coverage is a ‘density’ measurement, which is not
compatible with any current density standard and can only be used
for comparative analysis. For proper density measurements, we
recommend using a Beta Industries Densitometer conforming to
standards.
For the “Visual Coverage” value, a zeroing on the medium is needed.
The zeroing is done by a measurement on the sample (e.g. plate
background).