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100Module 14 of 15

Quality Assurance for Print

Delta E tolerances, registration issues, proofing types, and press checks.

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Quality Assurance for Print
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1) Executive Summary

The 7 most important insights
  1. Use the right measurement & viewing conditions first, then argue tolerances. Measure color under ISO 13655:2017 (M-series; typically M1) and view under ISO 3664 (critical P1 ~2000 lux D50 booth). Proofs/press sheets judged under mismatched conditions will fail good work and pass bad. [1],[2]
  2. Contract proofs (ISO 12647-7) are the legal color target. The 2016 revision tightened acceptance using ΔE00: average ≤ 2.5 and 95th percentile ≤ 5.0vs the target characterization; measured spot-color solids max ΔE00 ≤ 2.5. [3]
  3. Press acceptance is fit to the reference condition, not chasing instruments: use the appropriate characterization dataset (e.g., FOGRA51/52; GRACoL/CGATS21 CRPCs), verify solids/overprints/gray, and control tone (TVI/NPDC) per process. [4],[5]
  4. Registration tolerance: modern offset practice targets ≤ 0.10 mm center-to-center between any two colors. Flexo aligns register tolerance to line screen (≈ ≤ 2 ÷ linescreen, should be ≤ 1 ÷ linescreen). Design trap widths should reflect these realities. [4],[6],[7]
  5. Validation prints (ISO 12647-8) and soft proofs are guidance tools; they are not contract-binding but are useful for earlier stage approvals and remote workflows. [8],[9]
  6. Process control strips & targets matter. Use the Idealliance ISO 12647-7 control strip or Fogra MediaWedge with M1 measurement; record proof/press conformance. [10],[11]
  7. Change is coming. ISO/TC 130 has initiated a new revision of ISO 12647-2 (offset), and ISO 3664 updated in 2025—expect tighter harmonization and updated paper/ink data. Build QA to absorb updates. [12],[13]
3–5 actions to take now
  • Mandate M1/D50 for all measurements and P1 viewing for sign-off; document both on proofs and press reports. [1]
  • Adopt the correct reference (FOGRA51/52 in EU/UK; GRACoL 2013 CRPCs in US) and lock ICC profiles & verification templates to it. [4],[5]
  • Set explicit ΔE00 targets: proofs per ISO 12647-7; press solids/overprints/grays per your reference (e.g., GRACoL/PSO). [3],[5]
  • Write registration into the spec: 0.10 mmoffset (stricter for fine type/QRs); flexo register per linescreen; set traps accordingly. [4],[7]
  • Instrumented press checks: include MediaWedge/control strips on every form; verify solids, overprints, gray, TVI and register before “OK to print.” [10],[14]
Key risks & 12–24-month watchlist
  • Standards drift: pending ISO 12647-2 revision; update targets, curves, and training when released. [12]
  • Lighting transition: ISO 3664:2025 adoption and LED booth behavior; define transition timing and cross-site correlation. [13]
  • Paper OBAs: ensure M1 workflows; expect disputes if M0 remains in parts of the chain. [1]

2) Definitions & Concepts

Glossary (plain English)
  • ΔE: numeric color difference; ΔE00(CIEDE2000) is today’s preferred metric for perceptual uniformity in print QA (12647-7 uses ΔE00). [3]
  • TVI (tone value increase): “dot gain” curve; process- specific tolerances exist (e.g., ISO 12647-2). [15]
  • NPDC / G7: Neutral Print Density Curves; gray-balance calibration underpinning GRACoL/CRPCs. [5]
  • M0/M1/M2/M3: ISO 13655 measurement conditions; M1approximates D50 and is recommended with OBA papers. [1]
  • P1/P2 (ISO 3664): viewing conditions; P1≈ 2000 lux for critical comparison. [13]
  • Contract proof: ISO 12647-7-conforming, legally binding color target. Validation print: looser, non-binding (12647-8). [3],[8]
  • Registration: relative alignment of separations on press; measured as center-to-center deviation in mm. [4]
  • MediaWedge / control strip: standardized patch set for verifying proof/press sheets (e.g., Idealliance 12647-7 strip; Fogra MediaWedge). [10]
Concept map (bullets)
  • Inputs → Reference condition (FOGRA/CRPC) → Profiles → Proof (12647-7) → Press (12647-2/-6/-10 etc.)
  • Measurement (ISO 13655 M1) + Viewing(ISO 3664 P1) → Tolerances (ΔE00, TVI, register) → Sign-off
  • G7/NPDC ↔ TVI/gray balance; MediaWedge verifies proof; color barsverify press.

3) Standards, Regulations, and Governance

Core standards you will actually use
  • ISO 12647-7:2016 (Contract proofs). [3]
  • ISO 12647-8:2021 (Validation prints). [8]
  • ISO 12647-2:2013 (Offset print). [6]
  • ISO 12647-6:2020 (Flexo). [16]
  • ISO 13655:2017 (Spectral measurement; M-series). [1]
  • ISO 3664:2025 (Viewing conditions). [13]
  • ISO/PAS 15339-1/-2; CGATS21 CRPC datasets. [17],[5]
  • Fogra PSO/PSD & Idealliance GRACoL/G7 programs. [18]
Per-region notes
  • EU/UK: Fogra PSO (offset) and PSD (digital); references FOGRA51/52 and MediaStandard Print guidance (e.g., trap ≈ 0.1 mm basis from register). [4]
  • US: GRACoL/SWOP 2013 (CGATS21 CRPCs) with G7/NPDC; use Idealliance 12647-7 control strip. [5],[10]
What differs by region (quick table)
TopicEU/UK (Fogra/PSO)US (GRACoL/G7)
Reference datasetsFOGRA51 (coated), 52 (uncoated)CRPC1–7; GRACoL = CRPC6
Calibration focusTVI & colorimetric aims (PSO)NPDC/gray balance (G7)
Proof verificationFogra MediaWedge + 12647-7Idealliance 12647-7 control strip
Typical trap basis≈ 0.1 mm aligned to registerSimilar outcomes; spec via provider
Upcoming changes

ISO/TC 130 has initiated a new ISO 12647-2 revision (watch for potential gray balance alignment and updated paper data). Plan for profile & SOP refresh. [12]

4) Evidence Base & Benchmarks

Proof (ISO 12647-7:2016) acceptance
  • All patches vs ISO 12642-2 data: avg ΔE00 ≤ 2.5, 95th ≤ 5.0.
  • Spot-color solids: max ΔE00 ≤ 2.5.
  • CMY neutral scale: avg ΔCh ≤ 2.0, max ΔCh ≤ 3.5. [3]
Press (examples)
  • Offset TVI tolerances (ISO 12647-2:2013) vary by paper class; typical mid-tone bands ±3–±4 TVI points (confirm against your class tables). [15]
  • Registration: practice target ≤ 0.10 mm in offset; flexo ≤ 2 ÷ linescreen (aim ≤ 1 ÷ linescreen). [4],[6],[7]
Viewing & measurement
  • Viewing: ISO 3664 P1 ~2000 lux D50; specify booth class. [13]
  • Measurement: ISO 13655 M1 default; document instrument, aperture, backing. [1]
Where data conflict: tolerance philosophies differ (ΔEab vs ΔE00; TVI vs NPDC). Pin your reference, metric (ΔE00), and M/V settings (M1/P1) to avoid disputes. [3],[5]

5) Design & Production Implications

Rules of thumb (with cites)
  • Type/lines & register: For fine type, hairlines, or micro-features, assume ≤ 0.10 mm register capability in offset; increase traps or convert micro black text to K-only. Flexo: estimate register from linescreen early (≤ 2 ÷ LPI; aim ≤ 1 ÷ LPI). [4],[7]
  • Trap width: Start at ~0.10 mm on standard substrates and increase for large-format/light stocks; tie trap to register capability. [4]
  • Screens & angles (offset): 120–200 lpi typical; angles C/M/K ~30° offset; Y at ~15°. Platesetter at ≥2540 dpi for 200 lpi aims.
  • OBAs/M1: Mandate M1 and proof substrate class matching print class for tight ΔE00 on OBA papers. [1],[3]
  • Flexo on films: White backing and geometry affect measurement repeatability; specify backing in SOPs. [2]
Manufacturability flags
  • Slur/doubling distorts midtone gray and inflates TVI—fix mechanical print conditions before chasing color; use slur/doubling control patches. [14]
Supplier perspective

Converters expect: declared reference, measurement/viewing, tolerances(ΔE00/TVI/register), proofing method, and trap policy up front; otherwise arguments become subjective. [18],[5]

Designer tip: For small black text on color fields, make it K-only and increase backing-field trap rather than overprint C/M/Y text. [4]

6) Sustainability & Compliance

  • Documentation: Keep proof/press verification reports (M1/P1 stated), instrument IDs, and ΔE00/TVI/register logs with job masters for audits and scorecards. [11]
  • Evidence gap: peer-reviewed links between tighter color tolerances and reduced waste across all processes are sparse; a meta-analysis across PSO/GRACoL audits would help.

7) Workflow & Tooling

Checklists (ready to adapt)
  • Pre-press: reference (FOGRA/CRPC) locked → profiles embedded → output intent documented → trap policy set (mm) → black text K-only where possible → proof substrate class checked. [4],[5]
  • Proof (12647-7): MediaWedge present → M1 measurement → ΔE00 avg ≤ 2.5, 95th ≤ 5.0; spot solids ≤ 2.5 → report saved. [3],[10]
  • Press check: control strip present → solids/overprints/gray within aims → TVI/NPDC verified → register ≤ 0.10 mm (offset) or within flexo rule → P1 viewing. [4],[7],[13]
Decision trees (examples)
  • Choose proof type: Need legal, color-binding? → Contract proof (12647-7). Need speed/cost? → Validation print (12647-8) + caveats. Remote screen-only? → Soft-proof (certified) + hard proof pre-press. [8],[9]
  • If proof passes but press won’t match: Check viewing (P1?) → measurement (M1?) → mechanical (slur/doubling/register) → ink/substrate lot conformance → curve recal (TVI/NPDC). [13]
Calculator blueprints
  • ΔE00 calculator: Inputs L*a*b* target & measured (M1); outputs ΔE00; flag thresholds per 12647-7 and house press limits. [3]
  • Register-risk estimator: Inputs: process, linescreen, web/tension → suggests expected register and minimum trap (e.g., trap ≥ register × 1.5). [4],[7]
  • TVI/NPDC compliance: Compare measured TVI/NPDC to target (FOGRA/CRPC); red-flag midtone departures. [15],[5]
Template spec snippets (RFQ/COA)
  • Reference: “Print to FOGRA51 (M1) / GRACoL 2013 CRPC6; proof ISO 12647-7; P1 viewing.” [4],[5]
  • Tolerances: “Proof per 12647-7 (ΔE00 avg ≤ 2.5; 95th ≤ 5.0). Press solids per reference aims; register ≤ 0.10 mm (offset) / ≤ 2 ÷ LPI (flexo).” [3],[4],[7]

8) Category-Specific Notes

Beauty

High brand-color fidelity—spec spot-color solids ΔE00 ≤ 2.5 at proof (per 12647-7 spot clause) and tighter house limits on press for key brand colors; mandate M1. [3]

Food

Substrates with OBAs common; ensure M1 end-to-end; beware flexo register limits on small nutrition type; increase traps accordingly. [1],[7]

Beverage

Large solids & metallics; for metallics define evaluation method (visual under P1 + agreed patches); standard ΔE may not apply to effect pigments. (Evidence gap.) [13]

9) Case Studies

1) Global color alignment (offset, coated)
Approach: Adopt FOGRA51; switch to M1 booths/meters; contract proof per 12647-7.
Result: Proof avg ΔE00 ~1.6; press solids within aims; fewer disputes. [4],[3]
2) Flexo film with tight microtype
Approach: Register predicted at 0.25 mm from linescreen; traps increased to 0.3 mm; black microtype set to K-only.
Result: Zero rejections; generalizable method. [7]
3) G7 unification across sites (digital + offset)
Approach: Calibrate via NPDC; verify to CRPC6; proofing via 12647-7.
Result: Visual interchangeability; reduced make-readies. [5]
Replication plan: Capture instrument IDs (M1), booth spec (P1), reference dataset, ΔE00/TVI/register logs, slur/doubling readings, and waste sheets by make-ready stage.

10) Common Pitfalls & Red Flags

  1. M0 measurements on OBA stocks → inconsistent ΔE; always specify M1. [1]
  2. No declared reference → “What are we matching?” chaos. [4],[5]
  3. Chasing solids when gray/TVI are wrong → fix mechanics first. [14]
  4. Assuming perfect registration → set traps reflecting capability. [4],[7]
  5. Soft-proof-only approvals → use 12647-7 proof before press. [9]

15) References

Primary standards & programs: ISO 12647-7 (proofs) [3]; ISO 12647-8 (validation prints) [8]; ISO 12647-2 (offset) [6]; ISO 12647-6 (flexo) [16]; ISO 13655 (measurement) [1]; ISO 3664 (viewing) [13]; ISO/PAS 15339 & CGATS21 CRPCs [17],[5]; MediaStandard Print (bvdm) [4]; Idealliance control strip & programs [10],[9]; Fogra programs [11],[18]; TVI reference tables (example) [15]; register context [6],[7].

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