Reflectivity at glancing angles (Fresnel effect)
Surfaces reflect more light at glancing angles. Paint stronger edge reflections to describe solid, curved materials.
What it is
The Fresnel effect describes how surfaces reflect more light when viewed along their surface than when viewed straight on. A lake can look dark below you and mirror-like toward the horizon. A glossy table can reflect more along its far edge than at its center.
Bright reflection bands can appear near silhouettes and on edges turning away from you. Plastic, varnished wood, car paint, wet skin, and eyes can show stronger highlights and reflections in these areas.
Vary reflection strength across the object. Use local color and softer shading on front-facing areas. Increase value contrast and specular color as the surface turns away. Glossy materials may show a mirror-like band, while semi-matte materials show a gentler edge lift.
Why it matters
This effect helps materials describe curvature and their relationship to light. Weak control can make reflections appear pasted on, flatten spheres, and reduce the sense of weight in armor, eyes, and other forms.
You can check it when
- ✓Identify stronger reflections or value lifts at edges where surfaces turn away from you. They should follow the viewing angle, not appear randomly.
- ✓Repaint the same glossy object from a new camera angle while keeping the light direction fixed. The reflection should shift with the view.
- ✓Compare metal, plastic, and wet materials in your work. Their silhouettes should read as more reflective than their front-facing planes, even when details are simplified.
- ✓In a photo study, mark areas where glancing angles dominate reflection and areas where local color and shading dominate.