AM proofs and FM Presses: Resolving the Differences: Part 3 of 3

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FM screening is prized by high-quality printers because of the enhanced detail and expanded midrange color gamut it offers, but color matching to a conventional proof can be frustrating. Even though modern inkjet proofs use FM screening and show no visible dots, the widely-used GRACoL color model is derived from traditional AM press runs and is impossible to match directly with FM offset screening.

I touched on the reasons for the color differences in Part 1 of this series, and went over the creation and uses of device link profiles in Part 2. In part 3, we will explore the pros and cons of the two approaches to AM/FM color matching: match the press to the proof or match the proof to the press.

Option 1: Matching the Proof to the Press

An icc profile made from a characterization run of the press using FM screening can be used to create a proof that matches the color appearance of the characterization press run.

Pros:

  1. The proof becomes a good predictor of press color.
  2. Expanded FM midtone color gamut is preserved.
  3. No change in press workflow required.

Cons:

  1. Proofs will not match traditional GRACoL proofs
  2. Extreme accuracy is required when creating the profile: precise process control during the characterization phase is crucial.

Option 2: Matching the Press to the Proof

In this scenario, the FM press characterization profile is used to create a device-link profile for the plating workflow. In effect, the press is being treated much like an inkjet device.

Pros:

  1. Press can accurately match traditional GRACoL proofs
  2. Enhanced detail and freedom from visible screening is retained.

Cons:

  1. Color Gamut is limited to GRACoL range…potential expanded FM midtone gamut expansion lost.
  2. Specialized press workflow required.
  3. Extreme accuracy is required when creating the profile: precise process control during production runs is crucial.

The bottom line:

If your main reason for using FM screening is fine detail and freedom from visible dots, and if you need to match customer’s supplied proofs, choose option two and use device link profiles to match the press FM color characteristics to traditional GRACoL proofs. However, if you want both the fine detail of FM printing AND the expanded midtone color gamut that FM offers, chose option one and match your proofer to the press with carefully created icc profiles from characterization press runs.

Either way, process control is a must

Whichever approach you take to FM printing, process control is an absolute must, both during the characterization runs and during everyday production. The stake you put in the ground during characterization is something you will have to live with moving forward: if it is unreliable, un-typical or un-repeatable, success in color matching will be impossible.

Plate curves can be used to match FM press runs to G7 aims for NPDC; but the higher native dot gains (TVI) of FM mean that stronger plate curves must be used in order to achieve these NPDC aims, and stronger plate curves mean increased variability on press. This means that tracking of TVI for all 4 colors, already an important variable on a press using AM screening, must be tracked even more closely when printing with FM screening.

Ideally, the process control system should be used on every production job, not just during the fingerprint run. It should track all major parameters: solids, overprints, TVI (dot gain) and NPDC (gray balance plus contrast). And all measurements should be shared in real time with the prep department, so that any changes on press can be tracked and compensated for via plate curves adjustments before they result in visible color shifts. I use pressSIGN from Bodoni Systems, but a number of other systems are available as well: the important thing is to track the process, maintain stability, and respond to changes when necessary.

I always keep my posts informative and product promotion-free. If you are a buyer, brand owner or printer interested in the subject of color communication, please check out my other posts and browse my website for more information on achieving effective prep-press collaboration. If you would like to learn more about process control and brand color verification with pressSIGN, please click here. Or contact me directly at glenn@colorclarity.net

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