Noise Residual
Definition
The signal remaining after a denoising filter removes the scene component from an image. For PRNU estimation, the residual approximates the sum of PRNU and random noise. Averaging many residuals cancels random noise and isolates PRNU.
- Obtained by
- Subtracting a denoising filter's output from the original image
- Contains
- Sum of PRNU pattern and random noise
- Used for
- PRNU-based sensor fingerprinting
- Averaging effect
- Cancels random noise, isolates the PRNU pattern
Common questions
Why is a single image's noise residual not enough to identify a camera sensor?+
One residual is dominated by random shot noise and scene-dependent artefacts that swamp the faint, fixed PRNU pattern. Only averaging residuals from dozens of images from the same device suppresses the random component enough to reveal a stable sensor fingerprint.
What denoising filter is typically used to compute the residual?+
A wavelet-based denoising filter is the most widely used choice in PRNU literature because it separates high-frequency sensor pattern noise from the lower-frequency scene content more cleanly than simple averaging or Gaussian filters.
Related terms
- Camera Noise Model
- A mathematical description of a sensor's noise as a function of signal level, combining signal-dependent shot noise and signal-independent readout noise. The...
- CFA (Colour Filter Array)
- The mosaic of colour filters placed over a sensor so that each photosite captures one colour channel. The Bayer pattern (RGGB arrangement)...
- CFA Phase
- The spatial offset of the CFA mosaic pattern in an image. Pasting a region from a different image or after a non-CFA-aligned...
- Demosaicing
- The algorithm used to interpolate full-colour pixel values from the single-channel raw sensor data. Common methods include bilinear interpolation, gradient-based algorithms (AHD,...
- 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...
- Normalised Cross-Correlation (NCC)
- A scalar statistic in the range -1 to 1 that measures how closely the noise residual of a query image matches a...
- 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...
- Steganography
- Concealing one file inside another in a way that hides the existence of the hidden file. LSB image manipulation, JPEG DCT coefficient...
Explained in these topics
- Noise and CFA Inconsistency DetectionThe high-frequency component of an image obtained by subtracting a denoised version from the original. The residual retains camera-model fingerprint noise and...
- Photo Response Non-Uniformity and Sensor Fingerprinting