EN 
Why lighting can matter more than an expensive camera in machine vision
A scratch on a metal surface may disappear in a high-resolution image. Change the illumination angle and the same defect becomes obvious. In industrial machine vision, optical setup often matters more than adding a more complex algorithm.
Real-world demonstrations
KEYENCE — Machine Vision Lighting Selection Guide includes before-and-after imaging examples for glass edges, rubber parts and metallic outlines. These are vendor demonstrations, not tests performed by this site.
CCS — Machine Vision Lighting Applications shows practical lighting families and mounting options.
Four illumination approaches
| Lighting | How it works | Typical inspection |
|---|---|---|
| Backlight | Creates a high-contrast silhouette | Edges, holes, gaps and dimensional outlines |
| Low-angle / dark field | Grazing light makes surface defects scatter toward the lens | Scratches, burrs, dents |
| Ring / direct | Light surrounds the lens | Presence checks, labels, general inspection |
| Coaxial / dome | On-axis or diffuse illumination | Flat reflective parts, shiny surfaces, glare reduction |
No arrangement works everywhere. Reflective, curved and transparent workpieces need testing with actual samples.
A small-factory retrofit
For a cap-present inspection, fix the camera geometry, select illumination for clear cap edges, lock exposure and gain, then test thresholding or contour detection. A narrow presence/absence problem may not need AI.
For metal scratch detection, try low-angle lighting before upgrading the sensor.
What to validate
Compare good and defective samples under several lighting setups; judge feature-to-background contrast rather than perceived image quality; control ambient light; and account for motion blur, strobe timing and light aging.
Key idea: Make defects visible in a stable image before asking software to find them.
Sources: KEYENCE lighting guide · CCS lighting applications.
Independent technical analysis; demos and media belong to their cited sources.
Cover photo: PCB inspection lighting installation from planistar Lichttechnik, used as a lighting application example.