What is the purpose of a light meter in VT?

• A. To quantify illumination levels and ensure consistent, adequate lighting across inspections.
• B. To measure surface roughness.
• C. To record defect depth.
• D. To calibrate camera white balance only.

Answer: (A)

In visual and optical testing, the light meter is used to quantify illumination levels so lighting can be kept consistent and adequate across inspections. By providing a numeric value of brightness (like lux or foot-candles), it lets you set the lighting to a standard level and verify it stays within that level during the inspection. Consistent lighting helps prevent shadows, glare, or uneven illumination from masking or exaggerating surface features, making defect detection and comparisons reliable. The other options aren’t the primary role of a light meter: surface roughness is measured with different probes, defect depth with depth-measuring instruments, and camera white balance is adjusted by imaging settings or calibration steps, not by the light meter’s core function.