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100Module 5 of 15

File Preparation for Print

PDF/X standards, overprint vs. knockout, trapping per method, rich black builds, preflight checks before sending to converters.

8 minutes
prepress
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Lesson Video
File Preparation for Print
Module Content

1) Executive Summary

Top insights (5–7)
  1. Prefer PDF/X-4 or PDF/X-6 for modern workflows. X-4 (ISO 15930-7) preserves live transparency and ICC color; X-6 (ISO 15930-9, PDF 2.0) updates exchange for complex color/supply chains. X-1a forces flattening and CMYK/spot only. [1–4]
  2. Use ISO 19593-1 “Processing Steps” for packaging layers. Tag cut/crease/varnish/white ink etc. so downstream systems treat technical layers correctly. [5–8]
  3. Overprint vs knockout must be intentional and previewed. Black text typically overprints; white must never overprint—use a white-ink Processing Step. Always check with Overprint/Output Preview. [9–13]
  4. Trapping is process-dependent. Offset uses small traps; flexo larger; gravure varies; quality digital (e.g., Indigo) often minimal/none—confirm with converter. Don’t hard-code generic values. [14–18]
  5. Rich black builds must respect TAC. Typical TAC: GRACoL 2013 CRPC6 ≈ 320%; SWOP 2013 CRPC5 ≈ 300%; FOGRA51/PSO Coated v3 ≈ 300%. Choose builds with your converter. [19–21]
  6. Preflight to GWG 2022 where possible. Automate checks: fonts embedded, page boxes, resolution, spot/CMYK handling, overprint flags, TAC, Processing Steps. [22–26]
  7. For spot-tone control (esp. flexo), use ISO 20654 SCTV. Prefer SCTV over density-based TVI for predictable tints. [27–30]
Immediate actions (3–5)
  • Default export as PDF/X-4 (or PDF/X-6 where supported); embed the correct Output Intent ICC. [1–4,31]
  • Layer special operations with ISO 19593-1 Processing Steps (Cut, Crease, Varnish, White, etc.) as overprinting spot technical inks. [5–8,32]
  • Turn on Overprint/Output Preview and run GWG 2022 preflight before sending. [9–13,22–26]
  • Confirm traps and rich black with the converter’s spec (press, substrate, coating). [14–21]
Risks & watch-outs (12–24 months)
  • Growing adoption of PDF/X-6 (PDF 2.0) and expanded Processing Steps use. [2–4,22]
  • Increasing reliance on SCTV for spot tone control in flexo; update QC instruments/curves. [27–30]

2) Definitions & Concepts

  • PDF/X. ISO-constrained PDF for reliable print exchange; X-4/X-6 preserve transparency/ICC. [1–4]
  • Output Intent. ICC profile/identifier in the PDF describing intended print condition. [31]
  • Processing Steps (ISO 19593-1). Tag layers (OCGs) for dielines, varnish, white ink, etc. [5–8]
  • Overprint vs Knockout. Overprint stacks inks; knockout removes underlying inks. Preview required. [9–13]
  • OP/OPM. PDF overprint flags (fill/stroke) and overprint mode in graphic state. [12]
  • Trapping. Deliberate overlaps to mask mis-registration; strategy is process/substrate dependent. [14–18]
  • Rich black. K plus CMY for depth in large blacks; avoid in small type; respect TAC. [19–21,33]
  • TAC (Total Area Coverage). Max sum of CMYK to prevent over-inking. [19–21]
Concept map (bullets)
  • File format → PDF/X-4/X-6 → fonts embedded + page boxes → Output Intent drives soft-proof/conversions. [1–4,31]
  • Packaging layers → Processing Steps (cut/crease/white/varnish) → technical inks → control overprint/TAC. [5–8]
  • Rendering → Overprint/OPM + transparency → requires Overprint Preview. [9–13]
  • Printability → Trapping, TAC, resolution → verified via GWG 2022 preflight. [22–26]

3) Standards, Regulations, and Governance

Authoritative overview (US/EU/UK)
  • PDF/X (ISO 15930): X-1a, X-3, X-4, X-5, X-6 (PDF 2.0). [1–4]
  • Processing Steps (ISO 19593-1:2018): Metadata/constraints via OCGs for dieline/varnish/white, etc. [5–8,34]
  • Spot Color Tone Value (ISO 20654:2017): SCTV for spot tints. [27–30]
  • Print conditions & ICC: GRACoL/SWOP (US), FOGRA/PSO (EU/UK) with TAC constraints. [19–21]
  • Ghent Workgroup (GWG 2022): Preflight specs building on X-4/X-6 + Processing Steps. [22–26]
Per-region notes (selected)
TopicUS (GRACoL/SWOP)EU (FOGRA/PSO)UK
Default print conditionGRACoL 2013 CRPC6; SWOP 2013 CRPC5PSO Coated v3 (FOGRA51); PSO Uncoated v3 (FOGRA52)PSO/FOGRA widely used; ISO 12647 conformance
TAC (coated)~320% (CRPC6) [19]~300% (FOGRA51) [21]Typically 300% (PSO)
PDF/X expectationPDF/X-4 common; emerging X-6PDF/X-4 common; X-6 uptake in packagingSame as EU

Upcoming: Continued migration to PDF/X-6 and broader Processing Steps enforcement. [2–4,22–26]

4) Evidence Base & Benchmarks

Key sources summarized
  • PDF/X capability differences (flattening, transparency, ICC). [1–4]
  • Processing Steps tagging for dielines/white/varnish. [5–8,34]
  • Overprint behavior (OV/OP/OPM) per PDF Association/Adobe. [9–13]
  • Trapping mechanics and presets vary by tool/process; FIRST and Adobe docs as baselines. [14–16]
  • TAC and ICC constraints via GRACoL/SWOP/FOGRA registries. [19–21]
  • SCTV as spot-tone method in flexo. [27–30]
A) Typical TAC by print condition
ConditionTACEvidence
GRACoL 2013 CRPC6 (US, coated)≈ 320%[19]
SWOP 2013 CRPC5 (US, web)≈ 300%[20]
PSO Coated v3 / FOGRA51 (EU/UK)≈ 300%[21]
B) Indicative line screens & resolution planning
  • Offset: 150–200 lpi (effective PPI ≈ 2× LPI)
  • Flexo (labels/film): 85–150 lpi (screening tech-specific)
  • Gravure: coordinate with converter

Evidence gap: No single ISO sets LPI; use press fingerprint or FIRST guidance. [14,36–38]

C) Trap width ranges (illustrative; confirm)
ProcessIndicative trapNotes
Offset (sheet/web)~0.05–0.2 mm (0.2–0.6 pt)Depends on LPI, paper, registration; follow printer spec. [16,39]
Flexo (labels/film/corrugated)~0.2–0.4 mm+Wider traps common; verify via fingerprint. [14,40]
GravureVariableCoordinate with converter (no harmonized numeric standard).
Digital (HP Indigo)Often minimal/noneRegistration is tight; still confirm. [17,41]

5) Design & Production Implications

Rules of thumb (with citations)
  • Choose PDF/X-4 (or X-6) unless converter mandates X-1a; keep transparency live; attach Output Intent. [1–4,31]
  • Define page boxes (Media/Trim/Bleed); bleed ≥3 mm (EU/UK) or ≥0.125″ (US) unless otherwise requested. [1–4,42–44]
  • Enable Overprint Preview in Acrobat Output Preview and in design apps; simulate rich black/overprints. [9–13]
  • 100% K small text/linework generally overprints; avoid 4-color micro-type; never use Registration color in artwork. [9–13,45–46]
  • Rich black for large areas only, within TAC. Example (coated): confirm with converter; many choose ~C40–60/M30–40/Y30–40/100K within TAC. [19–21,33]
  • Processing Steps layers: set dieline/varnish/white as overprinting spot technical inks; tag per ISO 19593-1; exclude from print unless intended. [5–8,32,47]
  • Trapping: Prefer RIP/prepress traps per press profile; if designer-side traps required, follow printer values and Adobe trap settings. [14–16]
ChoiceCostColor stabilityRepro riskSustainability note
PDF/X-1a (flattened)LowLower (flattening artifacts risk)Higher with transparency/overprintsLegacy workflows only
PDF/X-4/X-6NeutralHigher (live transparency/ICC)Lower with proper preflightModern default
Rich black heavy buildsNeutralDark but risk set-offOver-inking/TAC riskMore ink → potential drying energy
Processing Steps taggingNeutralHigh (clean downstream)Lower (fewer manual fixes)Reduces errors/waste
Manufacturability flags
  • Hairlines <0.1 pt (offset) or <0.25–0.4 mm (flexo reverse) risk fill-in/breaks. [14,48–50]
  • Reverse text in flexo: bold sans-serif ≥5–6 pt; confirm with printer. [14,48–50]
  • Barcodes: manage quiet zones/magnification per GS1; verify with converter. (Pointer only.)
Supplier perspective (converter intake)

Correct PDF/X variant with Output Intent; fonts embedded; defined Trim/Bleed; Processing Steps tagged; no registration color; spot colors as spot; TAC respected; adequate resolutions; and a GWG-based preflight report attached. [1–4,22–26,31,45]

6) Sustainability & Compliance Considerations

  • Ink efficiency: Respect TAC; avoid unnecessary rich black—reduces set-off, drying energy, and waste. [19–21]
  • Right-first-time files: PDF/X-4/X-6 + Processing Steps reduce re-plates/makeready waste. [1–4,5–8,22]
  • Evidence gap: peer-reviewed LCA linking file quality to scrap is limited.

7) Workflow & Tooling (for PDA tools)

A) Checklists
Print-ready (designer handoff)
  • Export PDF/X-4 (or X-6) with Output Intent (target ICC). [1–4,31]
  • Set Trim/Bleed boxes (≥3 mm/0.125″ bleed). [42–44]
  • Convert intended process colors to CMYK/spot; confirm spot names.
  • Tag dieline/varnish/white via ISO 19593-1 Processing Steps as overprinting spot technical inks. [5–8,32]
  • Ensure fonts embedded; no Registration color in artwork; small text 100 K only (overprint). [45–46]
  • Check TAC against print condition; flag exceedances. [19–21]
  • Images: effective PPI suits LPI (~2× LPI rule); vector for type/line art. [36–38]
  • Overprint/Output Preview: simulate overprints & rich black; scan for “white overprint” errors. [9–13]
  • Run GWG 2022 preflight; attach report. [22–26]
Prepress (converter intake)
  • Validate PDF/X conformance and Output Intent match job ticket. [1–4,31]
  • Verify Processing Steps presence/colorant policy; suppress in print unless intended. [5–8,32]
  • Verify TAC, overprint flags, fonts, resolution, min line/type sizes, traps (house rules). [14–16,19–21]
B) Decision trees (to-be)
  • Pick a PDF/X variant: Need live transparency/ICC? → Yes → X-4/X-6; No/legacy RIP → X-1a. [1–4]
  • Overprint or knockout? Small black text/lines on color → Overprint 100 K. Pure spot over color and need purity → Knockout + trap. Never overprint white; use white-ink Processing Step. [5–8,9–13]
  • Trapping: If digital (Indigo) and house spec says none → none; otherwise RIP-based traps per press/substrate. [14–17]
C) Calculator blueprints
  1. Effective resolution: Effective_PPI = Placed_PPI / Scale_Factor; target ≈ 2 × LPI for CT images. Inputs: LPI, scale %. Output: min PPI. [36–38]
  2. Trap width seed (rule-of-thumb): Trap ≈ 0.5 × dot diameter; dot diameter ≈ 1/LPI (inches). Confirm via fingerprint. [39]
  3. TAC check: Sum CMYK per pixel/object; flag when Σ(C+M+Y+K) > TAC_profile. [19–21]
D) Template specs (to-be)
  • RFQ fields: Print condition (ICC), process, substrate, finishing, white ink Y/N, dieline source, min type/line specs, barcode grade target, TAC.
  • Artwork naming/versioning: {Project}_{SKU}_{Rev}_{Date}_PDFX4_{ICC}.pdf; Processing Steps layer names per ISO 19593-1.

8) Category-Specific Guidance

Beauty (labels, cartons). White underprint on clear/metallic substrates; multiple varnishes (spot/tactile) must be tagged via Processing Steps; small legal text → 100 K only, overprint; test trapping on foils. [5–8,32]
Food (flexible films). Flexo on films needs higher traps and larger min reverse type; SCTV recommended for brand spot tints. [14,27–30,48]
Beverage (cans, shrink). Complex die/crease/white/varnish stacks require robust Processing Steps tagging; confirm TAC vs coatings. [5–8,19–21]

9) Case Studies (proposed)

1. Label on clear film → washed-out brand red
Problem: No white underprint; designer used CMYK 0/0/0/0 “white”.
Approach: Add Processing Step: White (spot, overprint) under red; export PDF/X-4 with Output Intent; GWG preflight. [5–8,22–26]
Result: Brand red meets ΔE target; converter approves without rework.
2. Catalog X-1a flattening artifacts around soft shadows
Problem: PDF/X-1a forced flattening; stitching visible.
Approach: Switch to PDF/X-4; verify TAC/overprints in Output Preview; GWG preflight. [1–4,22]
Result: Cleaner output; reduced prepress edits.
3. Flexo snack pouch → gaps at color joins
Problem: Insufficient trap; thin reverse lines filling in.
Approach: RIP-based traps per FIRST; widen reverse lines; adopt SCTV for spot gradients. [14,27–30,48–50]
Result: Fewer visible seams; stable highlights.
Evidence gap: Public, quantified scrap/approval cycle reductions are scarce; replication plan would collect makeready sheets, ΔE stats, approval rounds, and plate remake counts across A/B jobs.

10) Common Pitfalls & Red Flags

  1. Exporting without Output Intent or with the wrong ICC. [31]
  2. White set to overprint instead of a proper white-ink Processing Step. [5–8]
  3. Using Registration color in artwork (marks only). [45]
  4. Four-color micro-text and rich-black small type → halos/mis-registration.
  5. Ignoring Overprint/Output Preview → surprises on press. [9–13]
  6. Over-TAC images causing set-off/drying issues. [19–21]
  7. Un-tagged dielines/varnish/white → printed by mistake. [5–8]
  8. Designer-side generic traps without converter input. [14–18]
  9. Missing/incorrect page boxes (Trim/Bleed). [1–4,42–44]
  10. Not embedding fonts; Type 3/emoji fonts sneaking in (preflight fixable).

15) References

Primary standards & specifications include PDF/X (ISO 15930), ISO 19593-1 (Processing Steps), ISO 20654 (SCTV), GRACoL/SWOP/FOGRA ICC registries, GWG 2022 preflight profiles, and Adobe/PDF Association guidance on overprint, flattening, and page boxes. See numbered citations [1]–[55] in the course handout.

Designer tips / Compliance watch / Manufacturing notes

  • Designer tip: In InDesign, set Appearance of Black appropriately and still check Output Preview; rich black warnings help spot unintended builds. [10]
  • Manufacturing note: For white ink, never try to “overprint white” as process white; define a spot white layer tagged as Processing Step: White (overprint). [5–8,32]
  • Compliance watch: Embed fonts and include page boxes; many PDF/X validators fail files lacking Trim/BleedBox per profile. [1–4,42]

Figures & visual prompts (to develop)

  • PDF/X family timeline (X-1a → X-6) with capability matrix
  • Decision tree: Overprint vs Knockout vs Trap
  • Processing Steps layer stack (Art vs Cut/Crease/White/Varnish)
  • Calculator UI mockups: Effective PPI & TAC inspector

Where numeric ranges are given (trap width, min line width, rich black builds), treat them as starting points and validate against the converter’s press/substrate profile. There is no single ISO numeric mandate; FIRST, GRACoL/FOGRA, and converter specs govern practice.

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