Which statement best describes oblique lighting's effect on edge features?

• A. It helps reveal edge features and cracks that direct lighting may miss
• B. It produces false positives
• C. It only highlights color differences
• D. It makes detection more difficult

Answer: (A)

Oblique lighting works by striking the surface from a side angle, so height differences along edges and cracks cast directional shadows and create stronger relief. That contrast makes subtle edge features become more visible, allowing cracks or separations that would be washed out under direct, perpendicular illumination to stand out. It emphasizes geometry and texture rather than color, so you’re seeing shape information rather than color differences. While any lighting can introduce shadows, oblique lighting is specifically used to enhance edge visibility and is not aimed at creating false positives; when interpreted correctly it helps detect features that direct lighting can miss.