What is one commonly recognized disadvantage of using visual testing (VT)?

Visual testing (VT) is a widely used non-destructive testing method, but it does come with certain limitations, one of which is its heavy dependence on lighting and visibility. For VT to be effective, adequate illumination is essential for the inspector to discern surface conditions accurately. Poor lighting can obscure defects such as cracks, corrosion, or other surface irregularities, leading to oversight of critical issues.

Moreover, environmental factors such as glare, shadows, or reflective surfaces can significantly impact the inspector's ability to see and interpret what is present. Since VT relies on the inspector’s judgment and visual acuity, any impairment in visibility can reduce the reliability of the findings. This reliance on favorable visibility conditions is a key reason why this choice stands out as a recognized disadvantage of visual testing.

In contrast, the other provided options reflect either advantages of visual testing or factors not inherent to its disadvantages, which illustrates why they do not align with the recognized limitations of this method.