Printing Plate - Techkon SpectroDens Manual

Printing Plate

Beside energy and focus of the laser, dot gain is the most important information
which has to be checked in plate exposure. Special plate measuring instruments
working with video analysis have been developed for this application; for example
TECHKON SpectroPlate. Compared to densitometers and colorimeters they offer
big advantages.
Nevertheless it is basically possible to make measurements with a densitometer on a
printing plate. In doing so one should regard the following: Variations in the coating of
the printing plates, may result in strong influences on the measurements especially in
the crucial range under 10 %. Variations of 0.02 D can cause errors up to 6 %.
The values measured with a densitometer do not correspond with the geometric dot
area, due to the fact that the densitometric measurement process is subject to optical
influences, which increase the measurement value. Therefore densitometers measure
always a higher value than video analysis devices. But the measurement value of the
densitometer can be taken as a reference value for the tonal value adjustment.
For the measurement of the zero point (1.), the solid patch (2.) and the screen patch
(3.) you should select areas on the printing plate which are located as close as pos-
sible to each other.
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2.
1.
Manual TECHKON SpectroDens Chapter 2 – Measurement functions
Now the corresponding current dot area is
indicated in the lower right section of the
display. In this case: 94.1 % dot area at 90 %
dot percentage results in a dot gain of 4.1 %.
The shaded area close to the curve shows
the tolerance range. The curve should be
within this area.
A wrong measurement can be easily deleted
by the red Escape button and the device will
be ready again to read the patch correctly.
With the Arrow buttons the vertical, dotted
cursor line can be navigated to display previ-
ous measurements.