Specular Highlight
Definition
A bright spot where a light source reflects directly off a shiny surface toward the camera. The position and shape of specular highlights encode the illuminant direction and the surface normal, and can be used to infer the light source position independently for each object.
- Field
- Digital image forensics
- Cause
- Direct reflection of a light source off a shiny surface
- Encodes
- Illuminant direction, surface normal
- Use in forgery detection
- Checking lighting consistency across composited objects
Common questions
How does a specular highlight expose an image composite?+
If two objects in the same photo were lit by a single source, their specular highlights should point toward a consistent light direction, and a mismatch between the highlight geometries on different objects can indicate one was inserted from a different source image.
Does the absence of specular highlights weaken this forensic check?+
Yes, the method only applies to sufficiently shiny or wet surfaces; matte objects rarely produce usable highlights, so an examiner needs other lighting cues, such as shadow direction, when highlights are not present.
Related terms
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- Photo Response Non-Uniformity (PRNU)
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- Photometric Stereo
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- Shot Noise
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