Normalised Cross-Correlation (NCC)
Definition
A scalar statistic in the range -1 to 1 that measures how closely the noise residual of a query image matches a reference PRNU pattern. Values near 1 indicate a strong match; values near 0 indicate no relationship.
- Value range
- -1 to 1
- Strong match
- Values near 1
- No relationship
- Values near 0
- Application
- PRNU-based sensor fingerprinting of images
Common questions
How is a match threshold set when using NCC for source-camera identification?+
Labs typically establish a decision threshold empirically from a reference dataset of known-same and known-different image pairs, since a single fixed cut-off is not universally reliable across cameras, image content, and processing history.
What can produce a misleadingly low or high NCC score?+
Heavy JPEG compression, image resizing, cropping, or strong content correlation between unrelated scenes can distort the noise residual and shift the NCC value away from what pure sensor-pattern similarity would otherwise indicate.
Related terms
- Flat-Field Image
- A photograph of a uniformly illuminated surface, typically a white wall or diffuser, taken at moderate brightness to avoid saturation. Used to...
- Noise Residual
- The signal remaining after a denoising filter removes the scene component from an image. For PRNU estimation, the residual approximates the sum...
- Peak-to-Correlation Energy (PCE)
- An extension of NCC that computes the ratio of the squared correlation peak to the energy of the surrounding correlation map. PCE...
- Photo Response Non-Uniformity (PRNU)
- A fixed-pattern noise component caused by microscopic sensitivity differences between individual sensor pixels. PRNU is deterministic and camera-specific, making it a sensor...
- PRNU Fingerprint
- Photo Response Non-Uniformity: the unique pattern of pixel-level sensitivity variations in a camera sensor, which acts as a device fingerprint. Used to...