What Stage Is In Greatest Need of Better Process Control?

Answered by Dan Remaley, Senior Technical Consultant Process Controls, PIA/GATF

Between proofing, platemaking, and printing, what stage of the process is in greatest need of better process control?

I believe that the major changes that occurred in prepress, namely CTP and digital proofing, dramatically changed the process. Prior to this, we output linear film and made plates and proofs with consistent results. Each product had a wide latitude for exposure and were pretty stable. The pressroom has changed with automation but the basic process has remained the same: ink, water, and paper. We still need process control, but the tools have been the same for years. Contrary to popular belief, linear plates will not allow you to match a print standard or a screen build book.

The two major problems are plates and proofs. The plate curves need to be adjusted so that the press can run the correct SID numbers and reproduce gray balance throughout the tone scale. Currently press operators move the SID values up or down to create a neutral sheet, this moves the values away from the standard. It also causes problems with trapping, overprint colors, and ink water balance.

Digital proofing has replaced the traditional halftone proofing systems. The general problem is that if the press calibration isn’t done correctly then the proof doesn’t match the press sheet. These systems are color managed by the use of an ECI 2002, or similar target. The press prints this target to the correct standards, and then the Lab measurements are transferred to the proofing device. These targets are compared and adjusted to give a visual match from press to print. Comparing a known value target, on every proof keeps the device from changing color in day to day operations.

This question was answered by Dan Remaley, Senior Technical Consultant Process Controls, PIA/GATF. For questions, comments or on-site help, contact Dan at dremaley@piagatf.org or (412)259-1814.
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