AM proofs and FM Presses: Resolving the Color Differences Part 1 of 3

FM screening makes it possible to create printing of ultra-premium quality: not only does it result in a print with no visible dots, but it also creates colors with greater purity and saturation, particularly in the quarter to middle tone range.

Greater purity of color is a great thing; however since industry-standard GRACoL proofing is based on color from AM press runs, we are faced with an inevitable difference between AM_based GRACoL proofs and FM printing.

To dramatize the effect, I will illustrate the difference with an image with elements that  show sensitivity to the appearance differences often seen between AM based printing (conventional dots) and FM based printing (stochastic): A golfer with a slightly tanned face, a neutral gray sweater, and a green fairway.

Golfer Cropped

Golfer Cropped

 

 

 

 

 

 

 

AM-based GRACoL Proof                                         AM-Based Offset Press Sheet

When we compare an AM press sheet with a GRACoL proof based on AM-based characterization press runs, we are apple-to-apple, and we can expect a good color match across all elements. But what happens when it is not apples-to-apples, and we are trying to match an FM press run to an AM-based GRACoL proof?

Golfer Cropped

Golfer Cropped FM

 

 

 

 

 

 

 

 

AM-based GRACoL Proof                                         Offset Press with FM Screening

Now, I have exaggerated the effect of FM screening on image color for purposes of clarity; but it’s easy to see why FM presents both opportunities and challenges to the printer.

Thanks to the G7 gray balance approach, the neutral gray sweater matches on both proof and press sheet, but other elements in the photo have shifted. The grass on the golf course certainly looks healthy; but it is now much brighter and doesn’t match the proof that was approved by the client, and the golfer’s now bright red face could be a serious problem.

Can’t we correct for that by adjusting the ink levels on press? Lets give it a try:

Golfer Cropped

Golfer Correct Face

 

 

 

 

 

 

 

AM-based GRACoL Proof                                       Offset Press with FM Screening

In this example, we can see that the press operator has done a pretty good job of matching the flesh tone color of the FM press sheet to the GRACoL G7 proof by reducing the magenta; but there is a problem: The sweater has turned green and the grass has become absolutely electric. Clearly this won’t fly. The press operator can’t control color selectively, so the overall change that helped the flesh tones has made the grass and the sweater worse.

How about the opposite approach? Could we add magenta to dirty up the grass and get a better match to the proof? The result isn’t hard to imagine but lets take a look:

Golfer Cropped

Golfer Correct Grass

 

 

 

 

 

 

 

AM-based GRACoL Proof                                       Offset Press with FM Screening

Well, no surprises here. The press operator has achieved a nice match to the grass, but now the sweater is purple and the golfer looks like he has been in the sun too long. What to do?

One fairly straightforward approach is to create an icc profile from an actual FM characterization press run and use it either in the  proofing queue, or else within the platemaking rip. This isn’t nearly as easy as it may sound, and there are tradeoffs to both approaches that must be considered.

I’ll cover the complications of custom profile based workflows as well as the pros and cons of both approaches in the next installment.

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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One Response to AM proofs and FM Presses: Resolving the Color Differences Part 1 of 3

  1. Ferran says:

    Hi Glenn, this is a very interesting article. I know of some printers here that have struggled with this. When printing with FM screening the tone value increase is very much higher than on prints with conventional AM screening. Some printers and consultants believe that they can solve this ONLY with new correction curves at the platemaking stage, but then the problem is still there. All what you explain here is true!

    I am looking forward to read the next part and to keep the conversation alive!

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