AM, FM, and new alternatives:

The Revolution and Evolution of Screening

Steve MusselmanSr. Manager, WW Business DevelopmentAgfa Corporation

Screening dates back to the origins of photography

1852 William Henry Fox Talbot patents photo-etching

uses a woven cloth screen to modulate tones of photographs.

1881 Frederick Ives

1882 Georg Meisenbach1890 Max and Louis Levy

1890s Max Perlmutter Early FM Screening?

100 years later…the FM Revolution

1993: The advent of Frequency Modulation.

Agfa’s CristalRaster1994 GATF InterTech award

Linotype-Hell’s Diamond screening

And, the Computer-to-Plate Revolution

1990: Advent of the “digital plate”.N90 photopolymer plate; variant of “projection plates”

1994: Advent of Computer-to-Plate.

Optronics, Gerber & Creo CTP products 1st to market

Now, in 2003, there are over 16,000 CTP systems installed world-wide.

With CTP, AM screening has reached its limit.

Amplitude Modulation:

Highlight and shadow detail can often be lost on press.

Frequency can now exceed engine addressability.

CTP quality can exceed press capabilities.

A CTP plate can resolve more than the press can hold.

10.6µ line Top:

Kodak Thermal(Imaged on Creo)

Middle:Agfa Silver (violet)(Imaged on Galileo)

Bottom:Agfa Thermal(Imaged on X45)

Printed SheetPlate

FM: fine, consistent dots; “grainy” midtones.

FM implies fixed size, controlled placement to generate tones.

Clustering often occurs in the mid-tones

Some 2nd order FM create swirls to minimize grain

Clustering

1st and 2nd order FM screening examples

Press-sheets:

Plates:

2nd: Luscher1st: Agfa 2nd: Creo

Trade-offs: AM versus FM screening

Each technology has its best fit.

175 lpi AM vs. 21 micronFM AM FM Rendering of fine details - +

Smooth flat tones + - Less Inherent Dot gain (TVI) + -

Press reponsiveness (ability to adjust colours)

+ -

Reduced Color Moiré - + Reduced Subject Moiré - + HiFi colour separations - + Extended Run length + -

Reduced clipping in highlights - + Rendering of midtones + - Open shadow details - +

Hybrid screening – trying to bridge AM & FM

Segmentation method

Specific AM & FM areas“Classic” Hybrid from Artwork Systems (PCC)

Stochastic distribution of AM dots

“Spekta” from Screen

XM: an alternative to AM, FM & Hybrid

Implemented via a single tiling algorithm

Patents awarded to Agfa: 1997 EU, 1998 US

Marketed by Agfa as :SublimaSimilar approach by Artwork Systems (Quantum)Similar approaches by Esko-Graphics and Creo (SambaFlex & MaxTone for Flexo)

XM = Cross Modulation

A screen that crosses smoothly from AM to FM

Not stochastic: FM dots at AM angles

• Stochastic implies random

• Highlight details may look stochastic, but are not.

• FM placement along existing AM angles of mid-tones.

• XM’s AM-to-FM transition point is line frequency dependent.

FM, XM & Hybrid screens side-by-side. (200x)

Agfa CristalRaster 21µ 1st order Heidelberg Satin 20µ 1st (?) order Creo Staccato 21µ 2nd order

Agfa Sublima 340 lpi XM screening Fuji 300 lpi CoRes AM Dithered Grey Screen Spekta Random AM 21µ

FM = increased gamut?300 lpi AM

FM attributes are really small-dot attributes.

Microdots are the primary cause of any measured/perceived gamut increase, rather than how they are organized.

175 lpi AM 340 lpi XM 21µ 1st order FM

What’s better: fine AM, XM or FM?

All are good – especially at rendering details.

XM & FM can have the same size minimum dot.

FM screens tend to show noise or grain in flat tints

AM & XM tend to show smoother flat tintsBut fine AM can clip (posterize) in highlights

340 lpi XM 21µ 2nd order FM

21µ 1st order FM 300 lpi AM

Take a closer look for yourself…

:Sublima Technology Overview

Printed using only CMYK – no spot colors!

Overall line screen used 340 lpi :Sublima.

Also compares 210, 240 & 280 :Sublima, and shows 21 micron :CristalRaster & 175 ABS.

The FM screening revolution of 1993 has just evolved…

AM, FM, XM, Hybrid…the choice is yours.

Thank you.