Colour Filter Array (CFA)
Definition
A mosaic of spectrally selective filters placed over a camera sensor so that each photosite measures only one colour channel. The standard Bayer pattern arranges filters as RGGB in a 2x2 tile; other layouts include Sony's RGBE (with an emerald filter) and Fujifilm's X-Trans 6x6 pattern.
- Standard pattern
- Bayer, RGGB in a 2x2 tile
- Sony alternative
- RGBE with an emerald filter
- Fujifilm alternative
- X-Trans, 6x6 pattern
- Forensic use
- Source camera identification via demosaicing artefacts
Common questions
Why is the CFA pattern useful for identifying a source camera?+
Each photosite records only one colour, so the missing two channels are interpolated by a demosaicing algorithm, and the specific interpolation pattern leaves periodic artefacts characteristic of the sensor and processing pipeline, which examiners can use to link an image to a camera model or even a specific device.
How does the X-Trans pattern complicate this analysis compared to Bayer?+
Because X-Trans uses a larger, less regular 6x6 tile instead of the simple repeating 2x2 Bayer tile, the periodicity of demosaicing artefacts differs, so detection methods tuned to Bayer-pattern cameras can fail or need adaptation for Fujifilm sensors.
Related terms
- Brown-Conrady Model
- The standard parametric model for camera lens distortion, using radial coefficients k1, k2, k3 and tangential coefficients p1, p2. Camera calibration tools...
- 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,...
- Device-Class Identification
- Establishing that an image was captured by one of a set of cameras sharing the same sensor architecture and firmware, rather than...
- Frequency-Domain CFA Spectrum
- When a demosaiced image is transformed into the frequency domain (using a 2D DFT), the CFA interpolation introduces periodic peaks at spatial...
- Radial Distortion
- A geometric lens aberration in which magnification changes with distance from the optical axis. Barrel distortion (negative radial coefficient k1) bows straight...