Photometric Stereo
Definition
A technique that recovers surface normals and illuminant direction from shading patterns. When applied to a single image, it uses local shading gradients and assumed surface reflectance models to estimate the illuminant direction at each surface patch.
- Recovers
- Surface normals and illuminant direction from shading
- Single-image use
- Estimates illuminant direction per surface patch
- Input relied on
- Local shading gradients and reflectance assumptions
- Forensic use
- Detecting spliced regions in image forgery analysis
Common questions
How does photometric stereo help detect a spliced or composited image?+
If a pasted-in object was photographed under different lighting than the rest of the scene, the illuminant direction estimated from its shading will not match the direction estimated from the surrounding region. That mismatch flags the area as a likely splice.
What limits the reliability of single-image photometric stereo for forgery detection?+
The technique assumes fairly uniform, well-behaved surface reflectance, so complex materials, strong shadows, or multiple light sources in the original scene can produce inconsistent normals even in an untouched image, which can generate a false lighting-mismatch signal.
Related terms
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- Shot Noise
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- Specular Highlight
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