Which statement best describes the limitations of visual testing (VT)?

• A. VT can detect subsurface defects with depth quantification under all lighting conditions.
• B. VT is limited to surface-visible defects, highly dependent on lighting and surface condition, cannot quantify depth reliably, and may yield false positives/negatives without proper methods.
• C. VT provides quantitative measurements of depth using calibrated lighting.
• D. VT results are independent of lighting and surface condition.

Answer: (B)

Visual testing is about what you can actually see on the surface under the given lighting and viewing conditions. Because it relies on human perception and illumination, surface condition (like dirt, coating, roughness) and how you light the part directly affect what defects appear, how clearly they show up, and even whether they’re seen at all. Since VT only reveals surface features, it cannot reliably reveal or measure anything beneath the surface, so you can’t quantify defect depth with this method. In addition, lighting and surface quirks can create artifacts or hide real defects, leading to false positives or false negatives if you don’t use proper lighting, standards, and procedures. Therefore the best description of VT limitations is that it detects only surface-visible defects, is highly dependent on lighting and surface condition, cannot quantify depth reliably, and can yield misleading results without proper methods.