Barcode grading standards measure how well a code is printed. ISO/IEC 15416 grades linear barcodes, ISO/IEC 15415 grades 2D codes such as Data Matrix and QR, and ISO/IEC 29158 adapts 2D grading to marks made directly on parts. GS1 then sets the minimum grade for each application, and GS1 South Africa tests barcodes for retail listing. This series explains each in turn and where an in-line reader fits.
What this series covers
Three ISO/IEC standards define how barcode print quality is measured and graded on a scale from 4 to 0. They do not say what grade is good enough: that is left to application standards, and for retail and logistics barcodes the application standard is the GS1 General Specifications. A barcode can therefore read on one scanner today and still fail a grade, or meet a grade and still be rejected for the wrong size or number.
The four chapters take one standard each. Chapter 1 covers ISO/IEC 15416 for linear barcodes and the 1.5/06/660 notation; chapter 2 covers ISO/IEC 15415 for Data Matrix and QR codes; chapter 3 covers ISO/IEC 29158 for dot-peen and laser marks on parts; chapter 4 sets out GS1’s minimum grades, GS1 South Africa’s verification reports and what an in-line reader can prove. The ISO texts are sold by ISO, so we work from ISO’s public abstracts and from what GS1 publishes openly, and say so where GS1 is the source.
addaScan integrates in-line code reading for South African production lines: every code is read and its content checked against the expected product, batch or serial. We do not supply barcode verifiers or formal grading. For a one-page overview, see our guide to barcode verification and grading.
Chapters
- 01What is ISO/IEC 15416 and what does it measure?How linear barcodes are graded from scan reflectance profiles, the 4-to-0 scale and what 1.5/06/660 means. · 6 min
- 02What is ISO/IEC 15415 and how does it grade 2D codes?How Data Matrix and QR codes are graded from an image, the 2D parameters and how GS1 writes a 2D grade. · 6 min
- 03What is ISO/IEC 29158 and why do DPM codes need it?Why dot-peen and laser marks on parts need their own lighting and grading, and how GS1 writes a DPM grade. · 5 min
- 04What barcode quality does GS1 require in South Africa?GS1 minimum grades by application, GS1 South Africa test reports for retailers, and what an in-line reader can prove. · 5 min
Which standard applies to which code?
The three ISO/IEC standards cover different symbols and marking methods, and GS1 then picks the minimum grade for each scanning environment. Find your code in the first column; the chapter link gives the method in full.
| Code or mark | Grading standard | How it is measured | Typical GS1 minimum | Chapter |
|---|---|---|---|---|
| EAN-13, UPC, ITF-14, GS1-128 (linear) | ISO/IEC 15416 | Scan reflectance profiles across the bars; each profile takes the grade of its weakest parameter, and the profile grades are averaged | 1.5/06/660 at the till; 1.5/10/660 in distribution | ISO/IEC 15416 |
| GS1 DataMatrix, QR, Digital Link codes printed on packs | ISO/IEC 15415 | An image of the whole symbol; matrix parameters such as grid non-uniformity and unused error correction | 1.5/12/660 at the till; 1.5/20/660 in distribution | ISO/IEC 15415 |
| Data Matrix dot-peened or laser-marked on parts | ISO/IEC 29158 (modifies 15415) | Image under defined angled or diffuse light, adapted to marks on metal and plastic | 1.5/06/660 (GS1 table 7, non-medical items) | ISO/IEC 29158 |
| Any of the above, for a South African retailer | GS1 General Specifications | GS1 South Africa tests to ISO methods and issues a report | The table for the scanning environment | GS1 quality in South Africa |
How do you read a grade like 1.5/06/660?
A grade is only meaningful with the aperture and light used to measure it, so GS1 writes all three together: minimum grade, aperture diameter in thousandths of an inch, and light wavelength in nanometres. ISO/IEC verifiers report four passing grades, 4 down to 1, and a failing 0; the older ANSI method uses A to D and F with the same thresholds (GS1 General Specifications, 5.12.5.1.2). GS1’s quick reference lists 1.5 as letter grade C and 0.5 as D (GS1 General Specifications, Table 5-43).
| GS1 notation | Minimum grade | Aperture | Light | Where GS1 uses it |
|---|---|---|---|---|
| 1.5/06/660 | 1.5 (ANSI C) | 6 mil = 0.152 mm | 660 nm | EAN/UPC at the till |
| 1.5/08/660 | 1.5 (C) | 8 mil = 0.203 mm | 660 nm | 2D codes on items not scanned at retail or in distribution |
| 1.5/10/660 | 1.5 (C) | 10 mil = 0.254 mm | 660 nm | ITF-14 on labels, GS1-128 and SSCC labels |
| 1.5/12/660 | 1.5 (C) | 12 mil = 0.305 mm | 660 nm | 2D codes on retail items, beside the linear barcode |
| 1.5/20/660 | 1.5 (C) | 20 mil = 0.508 mm | 660 nm | 2D codes on cases and logistic units |
| 0.5/20/660 | 0.5 (D) | 20 mil = 0.508 mm | 660 nm | ITF-14 printed directly on corrugate, or with X of 0.635 mm or more |
The aperture matters because it matches the size of the code. A small aperture on a large, coarse code exaggerates voids and specks; a large aperture on a fine code blurs narrow spaces. That is why the larger cases and logistic labels are measured with 10 or 20 mil apertures, and retail packs with 6 mil.
What does a failing report usually mean, and what fixes it?
A verification report lists a grade for each parameter, and the overall grade follows the weakest one in each scan. GS1 publishes the usual print causes and remedies for each parameter (GS1 General Specifications, 5.12.5.11–5.12.5.12). Most fixes sit with the artwork, the printer or the coder settings, not with the scanner.
| Report parameter | What it means | Usual print causes (GS1) | Remedies GS1 lists |
|---|---|---|---|
| Symbol contrast (SC) | Difference between the lightest space and the darkest bar | Background too dark or glossy; bars too light; contents or print showing through | Lighter, less glossy substrate; darker bar colour, more ink; opaque material or white underlay |
| Minimum reflectance (Rmin) | At least one bar must be no more than half as reflective as the lightest point (Rmax) | Bars too light | Darker bar colour, more ink or print head heat (watch bar gain) |
| Minimum edge contrast (ECmin) | Weakest contrast between a neighbouring bar and space; fails below 15 % | Recycled substrate with dark specks; uneven inking; elements too narrow for the aperture | More consistent substrate; even inking; larger X-dimension |
| Modulation (MOD) | ECmin as a share of symbol contrast: how even the contrast is across the code | Bar loss or gain, uneven inking, show-through, aperture too large for the X-dimension | As for ECmin; correct bar width adjustment |
| Decode | Pass/fail with the reference decode algorithm | Wrong encoding or check digit; gross bar gain or loss; defects seen as extra elements | Re-originate the symbol; correct the software; adjust press or printer; replace print head |
| Decodability | Margin left in the bar and space widths | Systematic bar gain or loss; rescaled digital images; flexo plate stretched across the print direction; ragged inkjet edges | Bar width adjustment; integer pixels per module; bars parallel to print direction; larger X |
Substrate sets a ceiling. GS1 notes that white paper typically reflects more than 75 % and black ink about 3 to 8 %, so black on white almost always reaches the top contrast grade. Brown corrugated board reflects between about 27 and 40 %, so even with a very dense ink it can never do better than the minimum passing grade for symbol contrast (GS1 General Specifications, 5.12.5.11.1). That is the reason for the lower 0.5/20/660 minimum for ITF-14 printed directly on corrugate.
Where does an in-line reader fit next to a verifier?
A verifier grades samples to the ISO method; a reader on the line checks every pack, but does not produce an ISO grade. In a South African plant the usual pattern is: artwork and first production checked by GS1 South Africa or an in-house verifier for the retailer’s listing (GS1 South Africa verification service); a reader on the line rejecting no-reads and wrong content on every pack; and periodic verifier checks during long runs. Chapter 4 sets out what each piece of evidence proves. A falling quality value on the line reader is a useful prompt for an extra verifier check, not a substitute for it.
addaScan supplies the in-line part. For the station see carton and pallet verification and DPM code reading; for which symbol goes where, see barcode basics.
Keep code data, print quality and line matching distinct
- Confirm identifier and data structure
- Select the symbol specification table
- Verify print quality to the specification
- Read and match each item on the line
A passing production read confirms decoding in that setup. A verifier report assesses the printed symbol under its stated method and settings. Neither substitutes for checking that the encoded identity belongs to the product being shipped. Preserve the application specification with the verifier report and the line recipe.
Questions about barcode grading standards
What are the barcode grading standards?
What is the difference between ISO/IEC 15416 and ISO/IEC 15415?
What grade does GS1 require?
Does addaScan grade barcodes?
Why does our ITF-14 on brown board only get a D?
What does a decode failure on a verification report mean?
Sources
- ISO/IEC 15416:2025, linear symbols (catalogue abstract) (ISO, read 2026-10-03)
- ISO/IEC 15415:2024, two-dimensional symbols (catalogue abstract) (ISO, read 2026-10-03)
- ISO/IEC 29158:2025, direct part mark (catalogue abstract) (ISO, read 2026-10-03)
- GS1 General Specifications, Release 26.0 (§5.12 barcode production and quality assessment) (GS1, read 2026-10-03)
- GS1 South Africa: barcode verification service (read 2026-10-03)
Have a line in mind?
Describe the product and the fault you need to catch. We test on your samples and reply with a feasibility note and a budget.