ifra - Nanyang Technological University

This document is downloaded from DR-NTU, Nanyang Technological 

University Library, Singapore. 

Title Digital screening process and FM screening. 

Author(s) 

Citation 

Date 1995 

URL http://hdl.handle.net/10220/1239 

Rights

ATTENTION: The Singapore Copyright Act applies to the use of this document. Nanyang Technological University Library 

Paper No. 13


Digital Screening Process 

& FM Screening 

• Advent of laser technology made it 

possible to mimic the photographic 

process of creating halftones. 

• Today's output devices comprise two 

parts - RIP and the Recorder 

• The RIP's function is collect and 

interpret incoming text and picture 

data and organize them into an 

electronic bitmap. 

• The recorder's laser is switched on 

and off to expose this bitmap on to 

the film. 

ifra 

• 

Page 1 

/ / ->


Creation of halftones 

In laser output devices clusters of laser 

dots (microdots) are exposed to 

produce the halftone dot 

Size of these clusters depend on the 

grey level information 

Number of grey levels 

- 2 

Output Resolution 

Line screen 

Example: 

Output resolution = 1360 dpi 

Screen ruling = 85 Ipi 

Grey levels = 256 

Page 2


Colour separations on 

imagesetters - requirements 

Each separation has to be screened at 

different angle ( 0,15,45 & 75) to 

avoid moire patterns 

Repeatability and accuracy of the 

recording engine for good registration 

Postscript implementation 

Postscript screening chronology 

• RT - Rational Tangent Screening 

• Supercell implementations 

• Improved quality 

• eg : Agfa's balance screening, Adobe's 

accurate screens, Linotype-Hell's high 

quality screening 

• Irrational screening - even better 

quality 

• FM screening 

Page 3


AM screening & FM screening 

• Conventional screening process 

produces dots of variable size but 

constant frequency, hence the name 

Amplitude Modulation (AM) 

• In Frequency Modulated (FM) 

screening dots of the same size are 

stochastically or randomly 

distributed 

FM screens vs regular screens 

Multi-color printing 

No occurence of overprint moire 

patterns 

No formation of rosettes 

Especially suited for Hi-Fi Colour 

applications (more than 4 process 

colours) 

Page 4



Tone reproduction 

No visible dot structure 

• continuous-tone appearance 

No dot corner link-up 

• smoother tonal transitions 

No trade-off between recording 

density, screen ruling and number of 

grey levels 

Hardware & software 

requirements 

Imagesetter with proprietary 

RIP software 

Postscript imagesetter with 

Macintosh software 

Page 5 


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Inputting 

• Scan resolution is not determined by 

screen ruling, but by 

• detail content of the image 

• quality level needed 

• throughput time 

• Special tone curve is required to 

compensate for higher dot gain 

-.> 

Recommended spot sizes 

For high-quality offset printing 

14 to 21 microns 

For newspaper printing 

21 to 42 microns 

Page 6 


• 

i 

* 



Recording Requirements 

Use of a hard dot film necessary 

Calibration of the imagesetter 

necessary 

Lower tolerances for film contacting 

Platemaking requirements 

high-resolution plate recommended 

(better than 6um according to 

UGRA/FOGRA) 

adjustment of the exposure time 

necessary (8um visible on the 

UGRA/FOGRA PCW) 

Page 7 




General requirement 

A well established quality control 

programme 

FM screening : Problems 

Special standard for platemaking 

necessary 

Adjustment of image gradation 

Tendency to graininess at lower 

recording densities 

Page 8 




Screening Methods tested 

Frequency Modulated Conventional 

Agfa : Crystal Raster 85 Ipi 

Crosfield: 100 Ipi 

Linotype-Hell: Diamond Screen 120 Ipi 

Scitex : Fulltone & Random 150 Ipi 

EMPA/UGRA : Velvet Screen 200 Ipi 

Higher screen rulings 


• 

With conventional screens, 130-150 Ipi 

prints the best results on normal , 

newsprint 

Compared to FM screening, these still 

show rosette-patterns, have moire and 

require high output resolution 

Page 9 



How about black & white 

For B&W, the FM algorithm has to be 

very good not to appear grainy 

Summary 

The times for 85-100 Ipi screen 

rulings are over 

Higher screen rulings (130 -150 Ipi) 

render far better print results 

Optimum print results can be 

achieved by using Frequency 

Modulation 

Page 10


Halftone imace 

'-:_," icrttninc. cortinoni lona 

unt~u cm ba ra;raducad on laiar 

pnMaft, i~j;ru"m and In prim 

Tha halftona calli in 

Ihit Image contitl 

c(4i4 liter doti 

which ma U 17 [nty 

lavad poitibte 

(IS-white). 

: Hallione dais generated by u&>^&$e&£m , :2&i 

Laser printers and Imagesetters 

Tha projatlion of a luar beam on p«?ar or ;~^^i;~ . -J'IM! 

era das >n alamantiry black tpot (cna thouund ol an if.;.- >


a viewing angle (angle o( ihe visual Held) 

O viewing distance (cm) 

d width ol a line pair (cm) 

R resolution power (line pairs/cm) 

Example 

d 20 lan(o/2) 

a =1.5' (minute of arc) 

D = 40 cm 

then: R = 28 7 (line pairs/cm) 

Resolution power of the human eye 

Definition of the terms frequency and amplitude in the 

screening technique 

amplitude modulation 

_ 

t 3 : 

£^^2 £4^*^-2 £•


Dot gain curves for FM screens printed on a non-heatset web 

offset press from negative plates 

Inking level: normal (IFRA values) 

Substrate: newsprint 

Dot gain % 

50 

45 

10 

35 

30 

25 

20 

15 

10 

5 

0 

. 

•^CZ^X 

Fulltone 1^1 

^ Diamond 

' i i 

Velvet N \ 

Crosfield 

102030 40 5060 70 80 90100 

Dol area film % 

Average dot gain curves for different screen rulings 

when printing from negative plates 

Inking level: normal (IFRA values) 

Substrate: newsprint 

Dot gain % 

'50 

0 10 20 30 40 50 60 70 80 90 100 

Dot area film % 

Page 13 

l


u 

RATIONAL SCREENING 

?£ % 

IRRATIONAL SCREENING

Halftone dot form 25% 

Arrangement of recording dots to produce a distance variable 

distribution 

Mffi:-=B 

ZMT. _ 

«T _ _Jmr 

^0 

BHS 

ft=o 

Aata CristalFtasler 

2Tnm 

T 1 : ! : 6 

*».• -..(*.. 

-/• . > i r . 

• .» %..*,.. . 

«... - I '. S 

1 

FM 

AM 

Dot patterns resulting from 6 FM screens and 3 screen rulings 

Dot area: approx. 25 % 

Magnification: 75 x 

Scitex Random 

20 jim 

— L 

• 

• . 

L 

1 • 

X 

• •• 

• • 

.V 

."w 

•..•_. 

. Tv* •- •» ••. 

r ^ i • . .k. 

r. •• .v 

t .- 

• 1 

1 1 .• .X. • *•* • *• .«. • i 

i 

••• 

Scitex Fulltone 

UGRA/FOGRA 

m 

15-25 jim 

Linotype-Hell 

Diamond 30 \im 

Velvet 41 \im 

• • •• S 

34 lines/cm (85 Ipi) 60 lines/cm (150 Ipi) 80 lines/cm (200 Ipi) 

^ 4 


Detail rendering ol an image reproduced with a FM screen 

and a conventional screen (magnification 5 x) 

FM screen spot size 30 Jim 

conventional screen 40 lines/cm (100 tpt) 

i


Niko Ruokosuo 

Research Manager, IFRA 

1976 CTP demonstration by ANPA/Laserite 

1980 First installation at Utica Daily 4" : ' 

1985 Dow Jones at the "Wall Steet Journal" 

1990 Hoechst Kalle N90 at DRUPA*90 

1991 Gerber installation at "Brabants Nieuwsblad" 

fi992};Gerber installation at "Alerta" ^ 

1993J Gerber installation at "Vorarlberger Nachnchten" 

1994 ilCrosfield in Magdeburg 

J1995 Krause in Lindau 

....._ ...... 



Figure 1 

I'" 

-«- 10 3 -, 

1 ,Q2 

f " 

£ JO> 

eft - 

I0" 1 - 

10 J - 

10" 3 

10-*- 

-Diazo positive 

;Diazo negative 

• Photopolymer 

! Electrophotographic! 

Wm Silver halide 

10*. 

300 ; 400 • . 500 600 .700 ' .800 900 .•;. looo . woo 

V/aveiength (run) 

H6echstN90 

- Photopolymer 

» thermal preprocessing . 

• light sensitive liquids 

• high quality and run length 

ip&$i>^%%*mmms&i


• Thermal Plates 

- Thermal Mask 

- Thermal Direct ?•---,:• 

- • daylight operation 

* • good run length 

.:;, • simple process 

^A future technology!!! 

• DRUPA'95 

46 suppliers showed CTP (partly OEM) 

• Number of suppliers increasing 

• Hybrid solutions.;• (Misomex) 

•?iVarious plate sizes 

^rgon-lon replaced by YAG 

Productivity increase (Optotech)


1. What percentage of my daily pagination can be 

produced totally electronically? 

2. How many plates must be produced at the peak 

time? 

3. What level of quality should be set for CTP? 

4. Which production control system or press presetting 

system should be chosen? 

5. How should the digital page data be stored? * 

6. What colour register accuracy does the 

manufacturer guarar 

7. How many plates can the pfete imager magazine 

hold? 

;


CTP - Qy sstiofts I© Ask 

8. How effectively is the plate interleaf paper 

removed, and how easily can jams be cleared? 

9. How well can the platemaking equipment be 

integ rated:- 

- plate developer equipment 

- automatic plate punch 

- automatic plate bender 

- plate scanner? 

Can an integrated control system monitor all 

these stages? If— 


CW - Questions to h$k 

10. Which printing plate to use? 

11. Must you or do you want to proof? 

12. Shall FM screening be used? 

13. What about backup? a


T~~ ' '.; s .-g^'-T- — —-?^~ 

• Simplified process 

• Later deadline for the last page 

• pavings in: 

- materials ':-„; 

- manpower iv; 

- costs (for single & double prod.) 

• Quality improvement 

• Easy use of FM-screens 

• Simple remake 

• Forces new technology and organisation


its,. Quality and Organisation 

Niko RuokosuG 

Research Manager. 1FRA 

pq pq [_| pr) 

1 "- II — II-—I 

W 

J 

5ii ;


;-—; ~—••:••» - — T p r r ^ 

&&&i&WMmi14 -.16 ^JlB-USO -£2 2* 

^ 

' ~ r ' 


Single production 

50-000 plates/year 

depr.


Pfefe&osts 

tOM. 

„ —___—_.—. - -dependson: 

• X—-—-————- recorder 

• Less working stages 

• Faster process (actuality) 

•No copying 

• Simple processing 

•eGood register 

•1 Clean plates 

• FM screening m


E 

J 70 

i *•"• 

r**, 

03 pattd trc m


Dsiaii rendition 

• Extremely good detail rendition and 

sharpness of image 

> Ideal for FM screening 

©fgnnte^tten 

• Platesetters are being positioned in 

the: * 

- editorial department 

- in the printing hall 

> no imagesetting^department 

> partial manning at platernaking 

>high skill-level required -/?': 

• • •\^'\-';^'t?'p " v ^--'"5 : ;' ; v- -"'•'•": '" ••••'• ' • / • ';>• 

.:.. • •••• •" ;•:•:' ' •":-.- •••'' - s ! ' - ' ' d ' - •" 

N ^ I- - .. ^ „ ~ ,-,_ •-,,-.


IN* 

W!W..^^.jK^N, •-, 

New developments at DRUPA 95 

Niko Ruokosuof-y • 

Research Manager, IFRA 

Recorders - examples 

• Creo 

-laser split to 480 beams 

•slower drum rotation 

• higher accuracy; 

- digital laser positioning control ace. to 

temperature 

• Escher-Grad 

: - molded composite materials for .'".••--' 

temperature changes 

- fast/ 35'sec• perflate at 1000 dpi 

:


: 

Recorders - examples i 

• Optotech 

-1 -5 exposing drums 

-1-3 developing units 

- 30 -120 plates per hour 

• Strobbe 

- simple technology (like pagefax) 

-prepunching 

-120 plates per hour 

. .,,, 

LJL-. 

• Krause 

-modular * 

•free choice of laser 

• free choice of RIP & Integration 

• Misomex 

- Laserstepper for 0 -100% digital 

material 

. - Platesetter for 100% digital 

'•>: s- Masterputich for optical punching Jafter 

imaging •'.'- i -':-|


• HighWater 

-manual load /tin-load 

- simple 

- economical 

• Gerber 

- most running installations 

• Basys 

- use of conventional plates 

-UV light source 

- "digital screen" steered by a PC


•:M. 

:Niko Ruokosuo v 

Research; Manager,.1FR A 

Pf^life^ momimiw? 

; Newspapers 

Books 

Commercial 

Business Forms 

Europe,• USA 

235 5 

60 130 

20 180 

60 70 

Total ?375 :385^ 

Source: Vantage Strategic Marketing; Derek Wyse 

«wiB!!'g : ""'" : '' 

wmrnmmmmtmmmm j£mMii**Mi^** v&iv'tmettfii^.' ^',.'' ., _.: I


Alerta, Sahtander, E, 

- Gerber LE 55, Hoechst N90 

Vorarlberger Nachn'chten, Bregenz, A 

- 2x Gerber LE 55, Hoechst N90 

prpler Tageszeitung, Innsbruck, A 

- Gerber LE 55, Hoechst N90 

Die Rheinpfalz/ Ludwigshafen, G 

- 6x DuPont Magnasetter 650, Silverltth 

Die Volksstimme, Magdeburg, G 

- Magnasetter 650, Silveriith 

Fuidaer Zeitung, Fulda, G * 

- Krause LSN, Hoechst N90 

Sydsyenska Dagbladet, Maimo, S 

- 2x Gerber LE 55, Hoechst Kl90 

8000 plates per month 

Sun Server at printing plant for ready pages 

Autoiogic soft RIP, 2 Power PC, 110 MHz, 8Gb 

All pages stored after RIPpirig 

1446 dpi, 50sec/plate, 35 plates/hour 

< 200.000 revs, 

FM screening in daily production 

OPC for advertising pages 

Good experience because of 

in-house engineering 



Same system as Vorarlb.Nachr. 

Problems with: 

- plates not square 

- toning 

- plate cassettes broke down 

- paper jams 

- register 

- processor (Ajax) 

System is not running until new recorder and 

"processor is delivered 

. 

m ZMtui 

Krause LSH, 68 plates/hour at 1016 dpi 

Eskofot2540 Scanner to digitise non-dig. pages 

Windows NT, 64 MB RAM, 1000 pages as bitmap * 

RlPping at prepress 

TCP/IP on 10BASE-T 

Telekom leased line 2Mbit/s


DIGITAL 

M 

PICTURE 

ARCHIVING 

The Virtual Library " 

11 A picture is worth a thousand words 

Please give two differences between 

a picture archive and a text archive , 

i 




COMPONENTS 

• Storage devices 

• Retrieval engines 

• Human interface 

• Magnetic discs 

OF A PICTURE ARCHIVE 

STORAGE DEVICES 

• Magneto-optical discs 

• CD-ROM 

• Photo CD Juke-Box 

2 




Picture formats and resolution 

• Thumbnails 

• Preview 

• High-Res 

RETRIEVAL ENGINES 

• Indexing the picture -> IPTC header 

• SQL or full text search 

• Boolean or natural language 

-> Picture description 

3 

i 

i 

jfra] 



HUMAN INTERFACE 

Give confidence to end-user 

• Local access to newspaper archive 

Remote access to picture data banks 

One archive for all kind of data? 

(Texts, pictures, graphics, ads, pages, video clips ... ) 

/ Probably, several data bases NV 

/ in the technical sense, 

/ but common user interface 

V that generates "hits" 

\ to whatever object meets the criteria. 

_» 

\ ' 

t 




A limited international survey . 

• U.S.A. : 

• U.K. : 

• Germany : 

• France : 

AP Preserver 

Cascade's MediaSphere 

Digital Collections 

Phrasea 

U.S.A.: AP Preserver 

Developed and marketed by Associated Press 

Server : Informix RDB on IBM RS 6000 

User interface : can be made similar to Netscape, • 

(access to external image banks through Internet will 

look similar to local access) 

Contacts : your local AP representative 

5 

H 



U.K. : Cascade's MediaSphere 

• Developed and marketed by Cascade, UK & USA 

• Server : Sun SPARC running Sybase RDB 

• User interface : Natural language search. Supports 

Adobe's Acrobat for previewing PostScript 

documents (typically, newspaper pages) 

• Contact (in U.K.) : 

-> fax,+ 44 171 538 5830 

-> e-mail, info@casuk.com 

[other offices: Andover (MA), Miami (FL)] 

Germany : Digital Collections 

• Developed by Digital Collections, 

marketed in USA by GMTI 

• Server : Unix workstation running own database t 

• User interface : closely linked with production 

database 

• Contact (in Hamburg, Germany) : 

-> fax,+ 49 40 2514121 

_; ifra 

•I i 

6


France: Phrasea 

• Developed by B&L Parentheses, 

marketed by partners worldwide 

• Server : Apple PowerMac 

• User interface : client has local access or remote 

(ISDN) access from Mac or PC (Windows, end 95) 

• Indonesia: Inmac, PT Jayakusuma Permai Data 

Malaysia: Votra Malaysia Sdn Bhd 

Singapore: Noisia 

Thailand: SPV Advance Corporation 

TechnoZone Corp. Ltd 

IMAGE SYSTEMS PLANNING 

• Get a good librarian (indexing is a key factor) 

• Scale the application: nb of users, nb of records, ... 

• Choose platforms for server and clients 

• Input/Output options: scanning, compression, image 

workflow, database maintenance, output for 

consultation/printing/on-line service 

• BOUM! 

Be efficient Once, Use Many times • 


7


WHAT MAKES GOOD QUALITY 

CONTROLLING QUALITY 

' THE DIFFERENCES BETWEEN GOOD AND AVERAGE QUALITY ARE SMALL • 

BUT THEY MAKE A BIG DIFFERENCE' 

'YOU CANNOT IMPROVE ANYTHING THAT YOU DO NOT CONTROL' 

ORIGINALS 

HIGH QUALITY PRINTING STARTS FROM HIGH QUALITYORIGINALS. AVOID: 

• UNDER EXPOSURE 

- BACK-LIGHT • 

- ARTIFICIAL LIGHTING CONDITIONS 

-UNSHARPNESS 

INPUTTING 

A SCANNER WITH CORRESPONDING SOFTWARE SHOULO BE SET SO THAT HIGH QUALITY IS ACHIEVED 

FOR 60% OF THE IMAGES BY USING THE DEFAULT VALUES AND SETTING THE BASIC ADJUSTMENTS 

(FOR EACH IMAGE): 

• SET HIGHLIGHT 

• SET SHADOW 

• CHECK MIDTONES 

• CHECK GREY BALANCE 

• CHECK FLESHTONES 

-SET SHARPNESS 

'DOING YOUR BEST IS NOT GOOD ENOUGH - YOU HAVE TO KNOW WHAT TO DO, AND THEN DO YOUR 

BEST' 

AN EXAMPLE OF ORGANISED CONTROL FOR IMAGE HANDLING 

PROCESSING 

THE VALUES MEASURED ON THE MONITOR MUST BE EXACTLY THE SAME AS ON FILM. 

THE VALUES ON THE POSITIVE PLATE MUST BE 3 V. LOWER THAN THE ONES ON FILM 

THE VALUES ON THE NEGATIVE PLATE MUST BE 3 % HIGHER THAN THE ONES ON FILM 

NO OTHER CHANGES MAY OCCUR 

PRINTING 

CONCERNING GENERAL PRESS PERFORMANCE; 

TECHNICAL LIMITS OF THE PRESS MUST BE DISTINGUISHED FROM EXCUSES 

THIS CAN ONLY BE DONE BY TESTING THE PRESS REGULARLY 

• BY RUNNING THE IFRA ACCEPTANCE TEST 

- BY RUNNING THE IFRA COLOUR TESTFORME 

DURING PRODUCTION - «» 

• DENSITIES MUST BE MEASURED AND CONTROLLED 

• REGISTER MUST BE ACCURATE 

• RUB-OFF AND SET-OFF ARE A PROBLEM TO 95 % OF THE NEWSPAPERS


«. PLATEMAKING 

PLATEMAKING IS CONTROLLED BY EXPOSING A PLATE CONTROL WEDGE WEEKLY 

RESULTS ARE RECORDED 

PRODUCTION CONTROL PHASE BY PHASE 

1. ORIGINALS 

NEWSPAPERS OWN PHOTOGRAPHERS ARE EDUCATED ABOUT OFFSET PRINCIPLES AND THEY ARE 

GIVEN A POSSIBILITY TO SHOOT DIFFERENT OBJECTS WITH DIFFERENT SETTINGS AND MATERIALS 

5. PRINTING 

DENSITIESARE MEASURED FROM THE PRINTED SAMPLES DURING PRINTING. 

CORRECTIONS ARE MADE IMMEDIATELY IN ORDER TO KEEPTHE VARIATIONS AT A LOW LEVEL. 

ADVERTISING AGENCY'S PHOTOGRAPHERS ARE GATHERED TO A DISCUSSION ABOUT PROBLEMS AND 

SOLUTIONS 

TESTPRINTS ARE PRINTED AND DISCUSSED 

S. DELIVERY 

2. SCANNING 

MAIL ROOM STAFF IS EDUCATED TO UNDERSTAND QUALITY DEMANDS AND THE IMPORTANCE OF THE 

MAILROOM OPERATION 

A TESTORIGINAL (INCLUDING HIGHLIGHTS, SHADOWS. FLESHTONES AND GREYS) IS SCANNED TWICE A 

WEEK INTO THE SYSTEM EVERY TIME WITH THE SAME SETTINGS. MEASUREMENTS ARE MADE FROM 

THE MONITOR AND DOT PERCENTAGES ARE RECORDED. THE IMAGE IS OUTPUT ON FILM AND THE 

FILMS ARE MEASURED FROM THE SAME POINTS. 

ALL RESULTS ARE PRESENTED ALSO AS GRAPHS AND ARE LATER GATHERED TO ONE POINT . 

A PERSON IN CHARGE. 

3. PAGE FACSIMILE 

PAGE FACSIMILE IS TESTED BY SENDING ATESTPAGE (CONTAINING 5% 50% and 90% FIELDS) 

REGULARLY, THE FIELDS ARE MEASURED AND RECORDED 

QUALITY HANDBOOK 

QUALITY HANDBOOK IS A TOOL TO: 

- AGREEONHOWTOORGANISE CONTROL 

• WHAT WILL BE MEASUREO 

•HOW OFTEN 

• BY WHOM 

• HOW ARE THE RESULTS HANOLEO 

• WHAT ARE THE TOLERANCES 

- WHAT IS DONE IF TOLERANCES ARE NOT MET 

-MAKE EVERYBODY INFORMED AND AWARE 

• AGREE ON EQUIPMENT AND MATERIALS TO BE USED 

• AGREE ON WORKING METHODS I? 

- DELIVER INFORMATION ABOUT THE WHOLE PRODUCTION CHAIN 

•SHOW RESULTS

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