Radiographic interpretation rewards a fixed order of thinking: establish that the radiograph is technically valid, describe what you see in measurable terms, and only then apply the acceptance criteria in the written technique. This article teaches that sequence through two worked film scenarios, a defect-appearance comparison table, an artifact-versus-defect discrimination habit, and a scored film-review drill. Treat administrative details — booking, eligibility, and current requirements — as questions for the certification body; see the issuer's site for those specifics.
Why image quality checks come before any defect call
A radiograph can only support interpretation after its validity is established: correct image quality indicator (IQI) visibility, density within the technique's specified range, and no backscatter evidence. Level 2 RT thinking starts with these checks, not with hunting for defects.
Two IQI designs dominate weld radiography, and they test different things. Wire IQIs encode sensitivity as the finest visible wire bridging the area of interest; step-hole or plaque IQIs encode it as visible holes of defined diameter in a stepped thickness. A wire IQI probes your eye for thin linear detail, while a step-hole IQI probes contrast resolution of small areas. Whichever the written technique specifies, your first interpretive act is confirming the required IQI detail is visible in the correct location.
The other validity gates are density and backscatter. Density is read with a densitometer and must fall inside the range the technique allows; outside that window, film contrast no longer behaves as designed and interpretation is compromised. Backscatter is checked with a lead symbol, usually the letter B, placed on the rear of the film cassette — if it appears faintly in the image, radiation scattered off the backing surface is fogging the film. Build the habit: validity first, then interpretation, then disposition, then documentation.
- Confirm IQI type, placement, and required detail visibility first
- Measure film density with a densitometer against the technique's stated range
- Inspect the image for the backscatter symbol before trusting contrast
- Only then begin characterizing indications
Geometric unsharpness: the calculation you should be able to defend
Geometric unsharpness is blur caused by the finite source size combined with source-to-object and object-to-film distances. A Level 2 computes it, compares it with the technique's allowance, and corrects the setup rather than interpreting a degraded image.
In simplified teaching form, Ug equals the effective source size multiplied by the object-to-film gap, divided by the source-to-object distance. Real setups also involve screen contact, focal spot condition, and motion, so treat the formula as a design check, not a guarantee of image quality. Work a labeled example: a 2.5 mm focal spot, a 10 mm object-to-film gap, and a 600 mm source-to-object distance give Ug = 2.5 × 10 ÷ 600 ≈ 0.04 mm. If a technique allows a maximum of, say, 0.5 mm at this thickness, the setup passes with wide margin — and shrinking the gap or lengthening the distance tightens it further.
Scenario 1 — the tempting shortcut. On a pipe weld with limited clearance, a colleague suggests shortening the source-to-object distance to cut exposure time, since the wall is thin anyway. The mistake is prioritizing exposure economy over unsharpness: at a short source-to-object distance the same gap produces large blur, fine wire IQIs lose definition, and the edges of crack-like indications soften. The better decision is to hold the required distance or reduce the object-to-film gap and re-shoot if needed. An unusable image produces an unusable report, however much exposure time it saved.
| Setup change | Effect on geometric unsharpness | Practical trade-off |
|---|---|---|
| Increase source-to-object distance | Reduces blur | Longer exposure time required |
| Reduce object-to-film gap | Reduces blur | May be impossible on complex geometry |
| Larger effective source size | Increases blur | Often chosen for shorter exposure |
| Smaller effective source size | Reduces blur | Lower output, longer exposure |
Separating genuine discontinuities from film artifacts
A dark or light mark on film is evidence of something — a discontinuity in the weld, or an artifact from handling, processing, screens, or the cassette. Discrimination is a deliberate habit: locate, compare, and correlate before naming anything.
Artifacts come with recognizable signatures. Pressure and crimp marks follow film handling and often show as sharp crescents or net-like lines unrelated to weld geometry. Developer splashes and drying streaks sit on the emulsion side and can appear on both films of a double-film mount in different patterns. Lead screen scratches, dirt, and poor screen contact produce repeated, sharply defined shapes. A useful habit: sketch the weld's expected geometry — fusion lines, root, cap, heat-affected zones — and ask whether each indication relates to that map. Discontinuities live in the weld; artifacts wander.
Scenario 2 — the linear trap. On a butt weld radiograph you see a fine, straight, dark line running just inside one fusion line. A rushed call names it slag inclusion and, because it is isolated, accepts it. The better decision: first check whether the line continues beyond the weld into the parent plate — if so, it is likely an artifact such as a screen scratch, since fusion lines are inside the weld. If it follows the fusion line exactly, consider lack of side-wall fusion, a planar discontinuity that most techniques reject outright regardless of length. The distinction changes the disposition completely, which is why characterization precedes any accept call.
Naming weld indications: the appearance vocabulary you need on the film
Interpretation is describing what the eye sees — shape, distribution, location, orientation, contrast — then mapping those observations to named discontinuities. Vague names like 'bad spot' have no place in a Level 2 report.
Anchor each discontinuity to its visual signature. Gas porosity appears as rounded, dark spots, singly or scattered, with sharp edges; shrinkage cavity is an irregular dark void. Slag inclusion shows as elongated, irregular dark lines or patches, often along the root or between passes, with less sharp definition than cracks. Incomplete penetration is a straight, dark line at the root centre, continuous or intermittent. Tungsten inclusion in TIG welds is the classic exception — it appears light, because tungsten absorbs more radiation than steel.
Cracks and planar flaws demand the most care. A crack reads as a fine, jagged, often branching dark line that may fade in and out of visibility, frequently transverse to the weld or running along the fusion boundary. Undercut is a dark line hugging the fusion line at the cap or root surface; excess penetration metal, burn-through, and concavity all show at the root and need positional reasoning. Practice narrating films aloud in this vocabulary — location, orientation, size, distribution — because that narration is exactly what a reportable description requires.
Turning a characterized indication into a defensible disposition
Acceptance is never a feeling. Once an indication is named, sized, and located, its disposition comes from the acceptance criteria in the written technique or referenced standard — and that citation belongs in the record.
Scenario 3 — the sizing slip. A radiograph shows a 6 mm elongated slag inclusion in the root of a single-sided weld, and the technique permits up to 8 mm of isolated slag but rejects any planar indication. Under time pressure you accept it on the length argument alone. The better decision is a two-step check: confirm the indication is truly volumetric — rounded ends, consistent width, no branching — before applying the slag rule at all. If it is planar, the length comparison never comes into play. The disposition matters because it follows a chain each link of which an auditor can retrace: validity, characterization, sizing, criterion, verdict.
Two habits make this chain fast rather than slow. First, write dispositions in the same order every time — validity result, indication description, dimension, criterion clause, verdict — so the reasoning is automatic under pressure. Second, treat borderline calls as re-look decisions: re-examine the film with an illuminated viewer in a darkened viewing area, adjust masking, and if doubt remains, follow the technique's provisions for additional exposures or angles rather than guessing in the direction of acceptance.
Reports and records: what a complete radiographic result contains
A Level 2 report links the film to its technique and inspection conditions: component identification, technique details, exposure and processing conditions, film evaluation, and the signed disposition. Missing links make even a correct interpretation unverifiable.
Trace one complete record to see what must survive on paper. Component and weld identification tie the film to a drawing location. Technique information — radiation source or energy, film and screen system, IQI type and placement, distances — ties it to the written procedure. Processing records tie it to a controlled darkroom outcome, since density and artifacts depend on it. The evaluation section then carries your described indications, dimensions, and the acceptance criteria applied. Every downstream reviewer should be able to reconstruct the decision from the page alone.
Level 2 responsibilities also include custody and organization of the film or digital images for the retention period the contract requires, and knowing when to escalate. A Level 2 interprets to a technique and issues reports for acceptance; questions of technique development, procedure qualification, and interpreting ambiguous code provisions belong to Level 3 or engineering authority. Practicing this boundary — what you sign, what you pass upward — is part of professional readiness, not just paperwork discipline.
A film-review drill and a preparation sequence you can adapt
Prepare by drilling the interpretive chain on real or reproduced films, scoring yourself against a rubric, and sequencing your study from image formation through processing, validity, interpretation, and dispositions.
The drill: obtain a set of weld radiographs — training films, reproduced images from textbooks, or films archived from supervised work. For each film, complete a one-page chain sheet: (1) validity — IQI visible, density, backscatter; (2) indications — location, shape, orientation, size; (3) name each indication; (4) disposition with the criterion you applied. Score one point per completed link and half-points for descriptions without dimensions. Re-run the same films a week later without notes; stable scores indicate the chain is internalized. These are learning milestones for your own tracking, not predictions of exam performance.
An adaptable sequence: weeks one and two, image formation and geometric principles — do Ug calculations by hand until setup changes feel intuitive. Weeks three and four, film and screen systems plus processing, since density and artifacts only make sense with this background. Weeks five and six, validity checks and interpretation drills with the chain sheet. Final stretch, mixed films under time limits, plus documentation practice writing full reports. Keep a personal log of every indication you misnamed; your log is a better syllabus than any generic list. For administrative matters such as eligibility, booking, and current certification requirements, consult the certification body rather than study notes.
- Score each drill film on four chain links: validity, description, naming, disposition
- Keep a misnamed-indication log and review it before each drill
- Sequence study: image formation → film/processing → validity → interpretation → dispositions → reporting
- Practice writing full reports, not just making accept/reject calls
References and further reading
Use these references to explore the concepts and check the latest information from the relevant organizations.