Hello Florian,
Thanks for your response to my email.
You said:
Given the CIELAB measurements of 50% yellow
are blueish compared to the aim values (e.g.
due to a blueish paper tone or blueish yellow
ink) - how should a printer correct this?
The linkage of density and CIE L* does not
work as well - even substantial increase/
decrease of yellow density almost does not
change the L* value.
In case of TVI differences process control
is clear (increase/decrease density, make new
plates, etc.)
I am sorry; I guess I didn't explain the idea clearly. The proposal was to use dE
(which is derived from the Lab measurements) just as you use TVI estimates today - purely
as a means of process control.
Today instruments measure the density of the paper, the density of the solid and the
density of a tint and using an approximate calculation estimate %dot for that tint.
Printers then compare the '%dot' value currently achieved against their aim
'%dot' value.
In the proposed scheme instead of measuring density, instruments would measure Lab of the
paper, Lab of the tint and possibly Lab of the solid. >From these measurements the
colour difference (dE) from the paper is calculated - this could be scaled so that the
solid becomes '100'. Users in this case would compare their measured value with
the aim value and adjust the process as they do today.
In addition to this measure, the solids would be measured using Lab which ensures that
problems of different inks and ink contamination can be detected [which cannot be seen
using a densitometeric approach].
Best regards,
Craig Revie
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