Chromatic Aberration
Definition
Colour fringing at high-contrast edges caused by differential refraction of light wavelengths by a lens. The pattern is lens-specific and inconsistent across a splice boundary where content from a different lens is inserted.
- Cause
- Lens refracts different wavelengths of light by different amounts
- Visible as
- Purple, green or red fringes at high-contrast edges
- Worst location
- Near the frame periphery and at wide apertures
- Forensic use
- Detects splicing when fringe pattern breaks across a boundary
Common questions
Why does aberration differ between two genuine photos from the same camera?+
Fringe direction and intensity depend on the subject's position in the frame relative to the lens centre, so two crops from different parts of the same original image can show different, both authentic, fringe patterns.
What defeats a chromatic aberration check?+
An inserted region can be edited to add matching synthetic fringing, or the whole image can be resized and recompressed, which smooths the colour edges and hides the discontinuity an examiner would otherwise look for.
Is it used alone to prove tampering?+
No, examiners treat an aberration mismatch as one corroborating clue and combine it with noise analysis, JPEG grid inconsistencies, and lighting or shadow checks before concluding an image was manipulated.
Related terms
- Affine Transform Estimation
- The recovery of the geometric transformation (rotation, scaling, shear) relating a copied region to its source, using matched keypoint pairs. Geometrically consistent...
- Block-Matching
- A copy-move detection strategy that divides the image into overlapping fixed-size blocks, computes a compact feature vector per block, sorts vectors, and...
- Copy-Move Forgery
- An intra-image manipulation in which a patch copied from one location within the image is pasted over another location in the same...
- Localisation Map
- The output of a forgery detection algorithm that marks, at pixel or block resolution, which regions of the image are identified as...
- Noiseprint
- A CNN-based camera-model fingerprint extractor by Cozzolino and Verdoliva. Applied to deepfakes, it reveals inconsistency between the camera fingerprint in the genuine...
- Passive Forgery Detection
- Detection that operates on the image data alone, without any pre-embedded watermark or signature. Distinguished from active methods such as digital watermarking...
- SIFT (Scale-Invariant Feature Transform)
- A keypoint descriptor algorithm that detects interest points and computes 128-dimensional descriptors invariant to scale and rotation. In forgery detection, matching SIFT...
- Splicing
- An inter-image manipulation in which content from one or more external images is inserted into a target image. Splicing introduces cross-boundary inconsistencies...