Last Updated: 18/01/2016
press and prepress analysis equipment
measurement of printed jobs and of proofs has never been more important than today.
reliable and easy to understand information
is at the forefront of modern process control
Measuring colour in the press-room and on proofs
The ability to reliably and accurately measure printed colour as well as tone is a necessity - since todays colour printing standards are specified as L*a*b* numbers.
It is not possible to actually specify on-press colour as density, since printed colour depends greatly on many factors, including ink, paper and fount solution. Once colour is achieved under controlled circumstances then density can be used for running, day to day.
In the press-room, accurate diagnostic equipment is of utmost importance if standards are to be maintained. If the press is to be run to numbers then the densitometer or spectrophotometer used at press-side to assess the printed sheet must be known to be accurate and well maintained as well as being regularly calibrated.
It is imperative that when plates are checked (ideally regular checking is in place as a policy), that checking is done with a good video plate reader. Density based plate readings are not quite accurate enough.
Process Control on press
It is possible to control press output day to day using, for each ink, only solid ink density and two *TVI (dotgain) readings, perhaps at 40 and 80 percent as specified in the ISO standard. However, if the press were to misbehave only in areas outside two commonly monitored TVI areas, printed work might still suffer and the printer’s job in matching proofs and maintaining grey neutrality become much more difficult with make-ready time is increased.
This means that monitoring carried out using a simple densitometer, which cannot practically give a picture of TVI, nor any indication as to achieved colour, is only part of the overall process control job.
*the term TVI, for Tonal Value Increase is now the accepted term for what we previously referred to as "Dot–Gain".
:: More to come here on diagnostic applications and hardware solutions ::
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